http://informahealthcare.com/dre ISSN 0963-8288 print/ISSN 1464-5165 online Disabil Rehabil, 2015; 37(8): 712–720 ! 2014 Informa UK Ltd. DOI: 10.3109/09638288.2014.940428
RESEARCH PAPER
Association between muscle power impairment and WHODAS 2.0 in older adults with physical disability in Taiwan Kwang-Hwa Chang1,2, Hua-Fang Liao3, Chia-Fan Yen4, Ai-Wen Hwang5, Wen-Chou Chi6, Reuben Escorpizo7,8,9, and Tsan-Hon Liou2,10 1
Department of Physical Medicine and Rehabilitation, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan, 2Institute of Injury Prevention & Control, Taipei Medical University, Taipei, Taiwan, 3School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan, 4Department of Public Health, Tzu Chi University, Hualien, Taiwan, 5Graduate Institute of Early Intervention, Chang-Gung University, Kweishan, Taoyuan, Taiwan, 6Department of Information Management, National Chung Cheng University, Jiayi, Taiwan, 7Department of Physical Therapy, Louisiana State University Health Sciences Center, New Orleans, LA, USA, 8ICF Research Branch of the WHO Collaboration Centre for the Family of International Classifications in Germany (DIMDI), Nottwil, Switzerland, 9Swiss Paraplegic Research, Nottwil, Switzerland, and 10Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, Taiwan
Abstract
Keywords
Purpose: To explore the association between muscle power impairment and each World Health Organization Disability Assessment Schedule second edition (WHODAS 2.0) domain score among subjects with physical disability. Methods: Subjects (60 years) with physical disability related to neurological diseases, including 730 subjects with brain disease (BD) and 126 subjects with non-BD, were enrolled from a data bank of persons with disabilities from 1 July 2011 to 29 February 2012. Standardized WHODAS 2.0 scores ranging from 0 (least difficulty) to 100 (greatest difficulty) points were calculated for each domain. Results: More than 50% of subjects with physical disability had the greatest difficulty in household activities and mobility. Muscle power impairment (adjusted odds ratios range among domains, 2.75–376.42, p50.001), age (1.38–4.81, p50.05), and speech impairment (1.94–5.80, p50.05) were associated with BD subjects experiencing the greatest difficulty in most WHODAS 2.0 domains. But a few associated factors were identified for the non-BD group in the study. Conclusions: Although the patterns of difficulty in most daily activities were similar between the BD and non-BD groups, factors associated with the difficulties differed between those two groups. Muscle power impairment, age and speech impairment were important factors associated with difficulties in subjects with BD-related physical disability.
Muscle power functions, older adults, physical disability, WHODAS 2.0 History Received 28 September 2013 Revised 22 June 2014 Accepted 27 June 2014 Published online 15 July 2014
ä Implications for Rehabilitation
Older adults with physical disability often experience difficulties in household activities and mobility. Muscle power impairment is associated with difficulties in daily life in subjects with physical disability related to brain disease. Those subjects with brain disease who had older age, a greater degree of muscle power impairment, and the presence of speech impairment were at higher risk of experiencing difficulties in most daily activities.
Introduction According to estimates by the World Health Organization (WHO), one billion or more people globally are disabled [1]. Disability refers to a person’s activity limitations and participation restrictions. Based on a medical model, disability is related to an illness or health condition [2]. However, as a multidimensional
Address for correspondence: Tsan-Hon Liou, MD, PhD, Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, 291 Jhongjheng Rd., Jhonghe, New Taipei City 235, Taiwan. Tel: +886-2-2249-0088 ext. 1600. Fax: +886-2-2248-0577. E-mail: [email protected]
concept, disability is accompanied by various types and degrees of body function impairment, creating different patterns of difficulty in daily living. Therefore, the combined consideration of an illness and impairment in body functions can offer more comprehensive information on disability [3]. Physical disability is one of the most common disabilities. Of those people with a registered disability in Taiwan, 35% have a physical disability [4]. In addition to activity limitations and participation restrictions, persons with physical disability often experience psychological distress [5,6]. The difficulty in daily life increases further if a person has both physical and psychological disorders [7]. The WHO Disability Assessment Schedule second edition (WHODAS 2.0) can offer comprehensive information for
Muscle power impairment and WHODAS 2.0
DOI: 10.3109/09638288.2014.940428
people with physical disabilities because of its psychometric properties [8]. People with neurological disease-related physical disability may result from either brain disease (BD), such as cerebral stroke, or non-BD, such as spinal cord injury. The impairments in body functions and difficulties in daily life might differ between those two groups because brain plays an important role on cognitive, motor control and speech functions. Most WHODAS 2.0-based studies on people with physical disability have investigated disabilities following a specific illness or health condition [5,6,8–14]. Scant literature has aimed at the extent of the difficulties in daily life for people with different causes of physical disability. Muscle power impairment is a common problem for people with physical disability [15] and can increase their difficulties of daily living [16]. However, few studies have linked impairment in body functions to WHODAS 2.0 domains. We hypothesized that persons with different causes of physical disability have different patterns of difficulty in daily life and that difficulty levels of daily life are associated with impairment degrees of muscle power functions. Therefore, we conducted this study to determine the difficulty level in each WHODAS 2.0 domain and to explore the association between muscle power impairment and each WHODAS 2.0 domain score among persons with physical disability.
Methods The Eligibility Determination System of Disability in Taiwan The rights of people with disabilities are protected by law in Taiwan. Since 1980, each citizen with a sequela or long-term functional impairment after illness can apply for disability evaluation. Within the Eligibility Determination System of Disability in Taiwan, an authorized physician evaluated and reported the applicant’s impairments or problems in body functions and structures using the official Disability Eligibility Determination Scale-version 1980 (DES-1980). DES-1980 has been implemented in Taiwan from 1980 to 2012. Beginning in July 2012, the disability evaluation processes changed under the amended Taiwanese law People with Disabilities Rights Protection Act. Based on the bio-psychosocial model and the International Classification of Functioning, Disability and Health (ICF) framework, the content of the official Disability Eligibility Determination Scale (DES-2012) has changed accordingly [17]. Completing the DES-2012 requires two or more authorized specialists. At least one physician evaluates the subject’s impairments in body functions and structures using the items related to ICF categories. Another interviewer evaluates the subject’s activity limitations and participation restrictions using the 36-item version of WHODAS 2.0 and the ICF categories regarding environmental factors. After training and becoming qualified, a professional specialist in the field of physical therapy, occupational therapy, speech therapy, psychology or social work for 1 year or more is authorized to be an interviewer for the DES-2012. Based on the ICF, WHODAS 2.0 was developed to assess the difficulty in daily activities and social participation experienced by a person in the prior 30 days. The WHODAS 2.0 has six domains. Domain 1, cognition or understanding and communicating (UC), includes six items; Domain 2, mobility, includes five items; Domain 3, self-care, includes four items; Domain 4, getting along with people (GAP), includes five items; Domain 5a, household activities (HA), includes four items; Domain 5b, work and school activities (WA), includes four items; and Domain 6, participation, includes eight items. The WHODAS 2.0 is closely linked to the ICF component d activities and participation [3] and is a reliable and helpful instrument to measure disability [9,18].
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Based on the WHO guidelines and permission, we translated WHODAS 2.0 into traditional Chinese version which was validated by the experts in the field of physical therapy, occupational therapy, psychology, linguistics and rehabilitation. The Taiwan Data bank of Persons with Disability In a pilot study from 2011 to 2012, we used the DES-2012 to assess 6244 individuals nationwide. Compiling the DES-2012 data of those 6244 individuals, we constructed the preliminary part of Taiwan Data bank of Persons with Disability (TDPD). The TDPD consists of each participant’s information, including gender, age, major caregiver, work or school status, area of residence [19], disability-related illnesses or health conditions, major impairment in body functions and structures coded as ICF categories, the scores of each WHODAS 2.0 domain, and overall score. Participants We recruited people who experienced neurological diseaserelated physical disability and had impairment in muscle power functions (ICF category b730) from the preliminary part of TDPD (Figure 1). We excluded those who were in a vegetative state or had dementia from the sample. Based on the primary disabling condition, we divided all participants into BD and non-BD groups. However, aging is an important risk factor for disability [20,21] and an age difference may exist between BD and non-BD groups. Focusing on the effects of muscle power impairment on the difficulties in daily living, we would like to eliminate the age difference from those two groups. Thus, those subjects younger than 60 years were also excluded in the study. Other potential
Figure 1. Summary of the recruitment processes of participants in this study and the participants’ distribution in each domain.
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risk factors for disability, including gender, major caregiver, work or school status, area of residence, disability-related illnesses or health conditions, and major impairment in body functions and structures were collected from the TDPD. Major caregivers included immediate family (parents, children, grandchildren and spouse), extended family (sibling and other relatives), and institution workers or friends. Work or school statuses included employed, housekeeping or retirement, and unemployment. Residence included urban, suburban and rural areas. The Joint Institutional Review Board of Taipei Medical University approved this study.
four impact values were added up. We added 1 point to the sum if the subtotal value of both arms equals the subtotal value of both legs because people with functional impairment of both arm and leg have worse outcome than those with either an arm or leg impairment [24]. Subjects experiencing a sum value of impact ranging from 1 to 3 points were identified as having a minimal degree of muscle power impairment. Conversely, 4–8 points represented mild impairment, 9–22 points represented moderate impairment, and 23–33 points represented severe impairment. The degree of muscle power impairment was coded along with ICF category b730 in the TDPD.
Measurements
Data analysis
An interviewer asked each participant to rate his or her difficulties (without any assistance of persons or devices) in doing each WHODAS 2.0 item using a 5-point Likert scale. On this scale, 5 indicates an activity that was done with extreme difficulty; 4, severe difficulty; 3, moderate difficulty; 2, mild difficulty; and 1, no difficulty. Based on the WHODAS 2.0 manual [22], the participant did not rate those items not experienced in the prior 30 days. Those items not rated were consequently recorded as missing data. The participant might often have extreme difficulty doing those items not experienced in the prior 30 days. Therefore, using the imputation procedure to handle missing data [22] might produce an underestimating bias in this study. We calculated standardized scores of each domain and the 32-item index on the basis of item-response theory and the WHODAS 2.0 manual [22]. Partly because of the participants’ characteristics of being older than 60 years and being physically disabled, only a few participants responded to items in the WA domain. Those items within the WA domain were excluded from the 36-item questionnaire. Therefore, we used the 32-item version instead of the 36-item version to evaluate overall disability in this study. To reduce the underestimating bias, we did not calculate the standardized score of each domain on a subject by subject basis, if any item within the domain had missing data. Likewise, we did not calculate the standardized score of the 32-item index if any item within the index had missing data. Consequently, the amount of data available for analysis decreased (Figure 1). The standardized scores ranged between 0 and 100 points, with higher scores represent more severe disabilities. We dichotomized all subjects and identified those with the greatest difficulty with a standardized score of 100 points in each domain and the 32-item index separately. Based on experts’ consensus, the classification of a person’s physical limitation associated with muscle power impairment was dependent on the grades of joint movement power and the joint location. This classification method was validated by experts and included in both DES-1980 and DES-2012 and has been effectively implemented in the Eligibility Determination System of Disability nationwide in Taiwan for decades. Within this system, an authorized physician evaluates the joint movement power of all weak joints. Each joint has three grades of movement weakness, from being totally paralyzed or having difficult in moving voluntarily or with a manual muscle testing [23] of Grades 0–1, being able to move but not against gravity or with a manual muscle testing of Grade 2, and being able to move against gravity or with a manual muscle testing of Grades 3–4. Because a joint has two or more directions of movement, the weakest power of movement was recorded for each joint. With reference to joint location, we weighed the weakness of each joint’s movement as part of the effect on muscle power impairment of a participant (Appendix). We calculated the sum of the impact values and estimate the degrees of muscle power impairment for each person. When four or more weak joints were evaluated, only the greatest
Using a Pearson Chi-squared test or Fisher’s exact test, we compared differences in clinical characteristics, the distribution of subjects with the greatest difficulty in each domain, and the distribution of subjects requiring assistance for performance for each domain between BD and non-BD groups. Using an independent t-test, we compared age differences between the BD and non-BD groups. Because the standardized scores of the 32-item index and each domain were not normally distributed (Kolmogorov–Smirnov test, p50.05), we used a Mann–Whitney U-test to compare differences in the standardized scores of the 32-item index and each domain between the BD and non-BD groups. We also used Spearman’s rank correlation coefficient (Spearman’s rho) to assess the agreement between the degrees of muscle power impairment and standardized scores of each domain. Spearman’s rho ranged from 0.3 to 0.6 was identified as showing moderate agreement [25]. We used logistic regression analyses with the stepwise method to assess risk factors for subjects with the greatest difficulty in each domain and in the 32-item index. Those variables found to have significant association with domain scores in the univariate analyses were entered into the model for multivariate analyses. The interactions of any two significant variables were also entered for analyses. Based on the results of the multivariate analyses, we estimated the probability of having the greatest difficulty in each domain. Using –2 log likelihood, we tested the goodness-of-fit of each logistic regression model. Using Cronbach’s a, we tested reliability of domain scores in both BD and non-BD groups. Using Cronbach’s a, we tested reliability of domain scores in both BD and non-BD groups. We analyzed data using the Statistical Package for the Social Sciences (version 15.0, SPSS, Chicago, IL), and did not analyze missing data. Therefore, the number of subjects in each domain was not identical (Figure 1). The differences between the groups and the correlations in the groups were considered significant if p values were 50.05. With Bonferroni’s correction for multiple testing, the score difference of each WHODAS 2.0 domain between the groups was considered significant if p values were 50.008.
Results We analyzed 856 subjects with physical disability related to neurological diseases from the preliminary part of TDPD from 1 July 2011 to 29 February 2012. Table 1 shows the basic and clinical characteristics of the participants. Subjects with BD included those with stroke (n ¼ 675), traumatic brain injury (n ¼ 24), brain tumor (n ¼ 10) and other BD (n ¼ 21). Subjects with non-BD included those with spinal cord injury (n ¼ 101) and peripheral nerve disorder (n ¼ 25). Table 2 shows the score distribution in each domain of both BD and non-BD groups. Except for the UC and GAP domains, the patterns of difficulty in other daily activities were similar between those two groups.
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Table 1. Basic and clinical characteristics of subjects with physical disability by brain disease (n ¼ 730) and non-brain disease (n¼126). Variable, unit Age, years Female Degrees of muscle power impairment Minimal Mild Moderate Severe Major caregivera Immediate family Extended family Institution workers or friends Work or school Employed Housekeeping or retirement Unemployment Area of residence [19] Urban Suburban Rural Coexisting impairments Speech impairment, yes Balance control impairment, yes Vision impairment, yes Hearing impairment, yes Need assistance for performance of each WHODAS 2.0 domain Understanding and communicating Mobility Self-care Getting along with people Household activities Work and school activities Participation
Brain disease
Non-brain disease
p Valueb
74.2 ± 8.7 328 (44.9)
74.5 ± 8.7 72 (57.1)
0.80 0.01 0.54
15 376 275 64
(2.1) (51.5) (37.7) (8.8)
3 60 47 16
(2.4) (47.6) (37.3) (12.7) 0.28
399 (85.3) 35 (7.5) 34 (7.3)
70 (92.1) 3 (4.0) 3 (4.0)
8 (1.3) 295 (46.8) 327 (51.9)
1 (0.9) 60 (53.6) 51 (45.5)
328 (45.2) 284 (39.1) 114 (15.7)
58 (46.0) 52 (41.3) 16 (14.8)
0.41
0.68
104 19 3 4
(14.2) (2.6) (0.4) (0.5)
0 2 2 0
266 546 594 222 257 41 360
(36.5) (75.1) (82.0) (30.6) (35.5) (18.1) (49.6)
44 89 101 42 59 5 69
(0.0) (1.6) (1.6) (0.0)
50.001 0.76 0.16 1.00
(34.9) (70.6) (80.2) (33.3) (46.8) (11.4) (55.2)
0.74 0.29 0.61 0.54 0.01 0.28 0.25
All data stated as number (%), except for mean age ± standard deviation. WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition. a Immediate family included parents, children, grandchildren and spouse; extended family included sibling and other relatives. b Using independent t-test for continuous variables and Pearson Chi-squared test or Fisher’s exact test for categorical variables.
With moderate degree of muscle power impairment, the score differences were significant in the domains for UC and GAP, yet indistinctive in mobility between the BD and non-BD groups (Figure 2). Except for the HA domain (Spearman’s rho ¼ 0.269), the scores of all other domains showed moderate agreement with the degrees of muscle power impairment (Spearman’s rho range among domains, 0.321–0.445, p50.001) in the BD group. By contrast, except for the mobility (Spearman’s rho ¼ 0.311, p50.001) and GAP (Spearman’s rho ¼ 0.319, p50.005) domains, most domain scores did not show good agreement with the degrees of muscle power impairment in the non-BD group. Compared to the non-BD group (Spearman’s rho ¼ 0.313, p50.05), the BD group (Spearman’s rho ¼ 0.470, p50.001) showed greater agreement between the degree of muscle power impairment and the 32-item score. Domain scores did not differ significantly between genders, major caregivers, work statuses and different levels of urbanization in the living area. Cronbach’s a of the responded items within each domain ranged 0.91–0.98 in the BD group and 0.90–0.99 in the non-BD group. The results of multivariate analyses showed that age, muscle power impairment and speech impairment were important factors associated with BD subjects experiencing the greatest difficulty in most WHODAS 2.0 domains (Table 3). By contrast, a few variables were identified for the non-BD group in the current study. The combined contribution of age and muscle power impairment to the estimated probability of having the greatest difficulty in each WHODAS 2.0 domain was similar between
BD subjects with (Figure 3) and without speech impairment. Compared to those who had speech impairment (Figure 3), BD subjects who did not have speech impairment experienced lower probability of having the greatest difficulty in each WHODAS 2.0 domain.
Discussion Using the preliminary part of TDPD, this study assessed the capacity of each WHODAS 2.0 domain and the overall 32-item index in older adults with physical disability related to neurological diseases and explored the role of muscle power impairment on the subjects’ difficulty in each domain. To our knowledge, this study is the first WHODAS 2.0 report on people with physical disability related to neurological diseases and muscle power impairments. More than half of the participants experienced difficulties in HA and mobility. Subjects of both BD and non-BD groups had similar patterns of difficulty in most daily activities, except that subjects with BD experienced greater difficulties in UC and GAP. Most domain scores and the 32-item score showed moderate agreement with the degree of muscle power impairment in subjects with BD. Those BD subjects who had older age, a greater degree of muscle power impairment, and the presence of speech impairment were at a higher risk of experiencing the greatest difficulty in most domains of daily activities. However, the association between most domain scores and the variables available in the study for subjects with non-BD was lacking.
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Table 2. Summary report of standardized scores of each WHODAS 2.0 domain in subjects with physical disability related to neurological disease.
WHODAS 2.0 domain
Subjects having the greatest difficulty (%)
Skewness (SE)
(40.0–100.0) (20.0–80.0) (35.0–100.0)
180 (28.8)a 13 (11.61) 193 (26.15)
0.6 (32.8) 0.1 (34.6) 0.5 (33.5)
(81.3–100.0) (81.3–100.0) (81.3–100.0)
387 (60.5) 74 (64.4) 461 (59.10)
1.7 (22.4) 1.8 (28.2) 1.7 (23.4)
(70.0–100.0) (50.0–100.0) (70.0–100.0)
226 (51.6) 37 (46.3) 263 (34.79)
1.4 (29.6) 1.1 (34.7) 1.4 (30.5)
(58.3–100.0) (41.7–100.0) (50.0–100.0)
180 (51.1)a 19 (27.9) 199 (26.78)
1.3 (30.0) 0.6 (37.4) 1.2 (31.8)
(100.0–100.0) (100.0–100.0) (100.0–100.0)
398 (81.6) 77 (73.3) 475 (61.45)
3.5 (18.2) 2.2 (28.6) 3.2 (20.6)
Median (IQR)
Understanding and communicating BD (n ¼ 626) 75.0 Non-BD (n ¼ 112) 55.0 Total (n ¼ 738) 70.0 Mobility BD (n ¼ 640) 100.0 Non-BD (n ¼ 115) 100.0 Total (n ¼ 755) 100.0 Self-care BD (n ¼ 438) 100.0 Non-BD (n ¼ 80) 90 Total (n ¼ 518) 100.0 Getting along with people BD (n ¼ 352) 100.0 Non-BD (n ¼ 68) 75. Total (n ¼ 420) 91.7 Household activities BD (n ¼ 488) 100.0 Non-BD (n ¼ 105) 100.0 Total (n ¼ 593) 100.0 Work and school activities BD (n ¼ 112) 14.285 Non-BD (n ¼ 16) 0.0 Total (n ¼ 128) 0.0 Participation BD (n ¼ 452) 79.2 Non-BD (n ¼ 96) 75.0 Total (n ¼ 548) 79.2 32-item index BD (n ¼ 209) 88.0 Non-BD (n ¼ 43) 83.7 Total (n ¼ 252) 87.0
(0.0–100.0) (0.0–75.0) (0.0–100.0)
41 (36.6) 4 (25.0) 45 (6.06)
0.1 (47.5) 0.8 (43.5) 0.2 (47.1)
(54.2–100.0) (47.9–93.8) (54.2–95.8)
114 (25.2) 19 (19.8) 133 (18.02)
0.8 (25.8) 0.5 (25.1) 0.7 (25.7)
(65.2–98.9) (48.9–93.5) (64.1–98.9)
50 (23.9) 7 (16.3) 57 (7.72)
1.0 (21.6) 0.9 (27.7) 1.1 (22.9)
WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition; BD, subjects with brain disease; Non-BD, subjects with non-brain disease; SE, standard error; IQR, interquartile range; 32-item index, the standardized score of 32 WHODAS 2.0 items. Those items within work and school activities domain were not included in the 32-item index. We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 points (least difficulty) to 100 points (greatest difficulty). a p50.001 (versus non-BD, by Pearson Chi-squared test)
Subjects of both BD and non-BD groups were prone to having the greatest difficulty in the HA and mobility domains, in which more than half of the participants had a domain score of 100. The HA and mobility domains are also the most difficult for persons with physical or sensory disabilities in other countries [13,26–28]. Difficulty in mobility can lead to an unsatisfying life [21,29]. The relationship between mobility scores and the degree of muscle power impairment might be independent of disabling conditions because the score difference in mobility was indistinct between BD and non-BD groups in each degree of muscle power impairment (Figure 2b). In addition, both groups showed moderate agreement between the values of mobility and muscle power impairment. Thus, the degree of muscle power impairment could independently represent the difficulty levels of mobility in this study. Although most of the participants experienced greater difficulty in the HA domain, less than half of the participants received help in performing HA tasks. A possible reason for this discrepancy is that numerous subjects having difficulty in HA could live well without participating in HA in Taiwan. Ethnic or sociocultural features of Chinese society, such as the commonly existing extended family, might partly account for this finding. Most participants lived with immediate or extended family in the study. Chuang et al. [30] stated that most patients with stroke in Taipei were cared for by family members or by a full-time foreign
attendant at home after leaving the acute hospital, and thus, were exempted from participating in HA. The preliminary ICF core set for post-stroke disability assessment developed in Taiwan also excludes any category related to ICF chapters d6 domestic life and d8 major life areas [25]. Whether persons with physical limitations were concerned with the difficulty of HA in Chinese society might require further study. Another reason for this discrepancy could be the lack of resources to assist HA performance. The requirements of persons with a disability may change in accordance with various patterns of daily life. Therefore, being aware of the pattern of difficulties in the different domains of daily living, and searching for the associated factors among people with a disability may be essential for the government to develop pertinent policies and to offer helpful programs to assist people in need. These tasks are the focus of this study. However, the influence of environmental factors on the performance of HA requires further investigation. Previous studies have used either one of the scores of the 12-, 32- or 36-item indexes to assess the overall difficulty of a person in daily life [12–14]. However, the frequencies of subjects having the greatest difficulty in mobility, self-care, GAP and HA domains in this study were considerably higher than the frequency occurring using the 32-item index. Using the 32-item index as a proxy, we excluded a number of subjects who experienced the greatest difficulty in these four domains. The significant
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Figure 2. Mean standardized scores of each WHODAS 2.0 domain with various degrees of muscle power impairment in subjects with BD (thick line) and subjects with non-BD (thin line). We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 point (least difficulty) to 100 points (greatest difficulty). *p50.008, yp50.001 (versus the non-BD group, Mann–Whitney U-test). Abbreviations: BD, brain disease; WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition. Table 3. Summary report of logistic regression analysis of potential risk factors of having the greatest difficulty in each WHODAS 2.0 domain in subjects with physical disability.
WHODAS 2.0 domain For subjects with BD Understanding and communicating Mobility Self-care Getting along with people Household activities Participation 32-item index For subjects with non-BD Understanding and communicating Mobility Self-care Getting along with people Household activities Participation 32-item index
Muscle power impairment 120.64 5.02 3.41 3.73 376.42 2.75 2.97
(8.21–1773.21)c (3.57–7.06)c (2.41–4.81)c (2.52–5.54)c (7.47–18975.35)b (1.96–3.85)c (1.85–4.79)c
– 2.44 (1.29–4.61)b 1.92 (1.01–3.66)a – 2.41 (1.16–4.99)a – –
Age 3.54 1.84 2.01 1.95 4.81 1.38
(1.84–6.82)c (1.48–2.3)c (1.56–2.58)c (1.47–2.59)c (2.24–10.32)c (1.07–1.78)a –
2.02 (1.00–4.08)a 2.17 (1.31–3.62)b – – 1.99 (1.11–3.56)a – –
Speech impairment 3.71 2.4 1.94 5.80
(2.2–6.27)c (1.33–4.32)b (1.04–3.62)a (2.72–12.37)c – – – – – – – – – –
Muscle power impairment Age
Goodness-of-fit statistics
0.63 (0.44–0.89)a – – – 0.52 (0.31–0.87)a – –
604.6 (19.5%)c 678.8 (21.0%)c 494.6 (18.5%)c 381.6 (21.8%)c 400.0 (14.3%)c 462.4 (9.5%)c 207.9 (9.6%)c
– – – – – – –
76.3 (5.1%)a 128.3 (14.4%)c 106.2 (3.9%)a 106.7 (12.4%)c
All data stated as adjusted odds ratio (95% confidence interval) for potential risk factors and 2 log-likelihoodintercept-and-covariates value (change %) for goodness-of-fit statistics, not significant data were not shown. The 2 log-likelihoodintercept-and-covariates change % ¼ [(–2 log-likelihoodintercept-only) (–2 log-likelihoodintercept-and-covariates)] 7 (–2 log-likelihoodintercept-only). Independent variables entered the analyses included age (10 years), muscle power impairment (minimal ¼ 1, mild ¼ 2, moderate ¼ 3, severe ¼ 4), speech impairment (no ¼ 0, yes ¼ 1), and the interactions between variables (including muscle power impairment age, muscle power impairment speech impairment, and speech impairment age) for subjects with BD, and included age, muscle power impairment and muscle power impairment age for subjects with non-BD. The interactions between variables, such as muscle power impairment speech impairment and speech impairment age, did not contribute significantly to any of the models and were not shown. Abbreviations: WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition; BD, brain disease; 32-item index, the standardized score of 32 WHODAS 2.0 items. Those items within work and school activities domain were not included in the 32-item index. We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 points (least difficulty) to 100 points (greatest difficulty). a p50.05, bp50.008, cp50.001.
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Figure 3. Estimated age- and muscle power impairment-specific probability of having the greatest difficulty in each WHODAS 2.0 domain in subjects with brain disease and having speech impairment. According to the degrees of muscle power impairment (diamond, minimal; square, mild; triangle, moderate; circle, severe), a serial of probability of having the greatest difficulty (standardized score ¼ 100 points) in each WHODAS 2.0 domain with age was estimated. The probability increased with age and greater degrees of muscle power impairment in most domains. The functions of the probability were concave down and increasing for subjects with moderate muscle power impairment and were concave up and increasing for subjects with minimal muscle power impairment in most domains.
differences in the rate of subjects having the greatest difficulty in the UC and GAP domains between BD and non-BD groups did not occur with the 32-item index. In addition, we included only one variable, muscle power impairment, in the optimal model to predict BD subjects having the greatest difficulty in the 32-item index. Only subjects with the most difficulty in all six domains could have a 32-item score of 100 points. Therefore, simply using the 32-item score could not uncover the difficulties in certain specific domains of daily living in subjects with physical disabilities. No consensus has been reached in the literature regarding the cut-off point of the WHODAS 2.0 score to identify persons with a substantial disability. Using normative data, Von Korff et al. [31] recommended that people with a WHODAS 2.0 score of 45 points should be considered substantially disabled [31]. However, the scores of our subjects were negatively skewed: More than 75% of our subjects experienced a 32-item score of 45 points. Therefore, we set the highest standardized score of 100 points as the greatest disability for each domain and the 32-item index in this study. Limitations This study explored the role of muscle power impairment on various difficulties in subjects with physical disability. However, this study has three limitations. First, the WHODAS 2.0 scores
showed a prominent ceiling effect in this study. Most participants in this study had a history of a stroke. Gallagher and Mulvany [28] reported that subjects with stroke have a higher 32-item score than subjects with other health conditions. The WHODAS 2.0 scores obtained from the TDPD might be overestimated because persons who are eligible for a disability can receive social welfare services (including a pension) in Taiwan. Second, the reliability of the classification method for assessing muscle power impairmentrelated physical limitation was not well documented although this method has been used by authorized physicians nationwide in Taiwan for decades. Besides, the individual joint movement power was assessed by the aid of manual muscle testing which is reliable [23]. Further study to investigate the reliability and to validate the usefulness of this classification method is needed. Finally, using the existing data from the TDPD, information about the grade of each joint movement power and the major location of impairment in the upper and/or lower extremities was lacking. Information about cognitive functions was also lacking. However, those subjects who were in a vegetative state or had dementia were excluded from the study. Besides, because this is a crosssectional study, we had no data to determine the changes of WHODAS 2.0 scores in response to any long-term changes in certain bio-psycho-social variables among persons with physical disability. Further study with a longitudinal design is needed to assess the changes of WHODAS 2.0 scores and muscle power impairment with time.
DOI: 10.3109/09638288.2014.940428
In conclusion, most subjects with physical disability had difficulties in the HA and mobility domains. Although the patterns of difficulty in most domains of daily life were similar between the BD and non-BD groups, factors associated with difficulties in daily activities were different between those two groups. The standardized scores of WHODAS 2.0 domains and the 32-item showed moderate agreement with the degree of muscle power impairment in subjects with BD. Those subjects with BD who had older age, a more severe degree of muscle power impairment, and the presence of speech impairment were more likely to experience greater difficulty in most domains of daily activities. Simply using the 32-item score could not uncover the difficulties in certain specific domains of daily living in subjects with physical disabilities. The combined consideration of age and impairments in muscle power functions and speech functions can offer more comprehensive information about difficulties in subjects with BD-related physical disability. Other factors not assessed in the current study may contribute to the difficulties in daily activities in subjects with non-BD and need further searching for.
Acknowledgements We thank Chien-Hua Wu, PhD, for his reviewing the statistical methods for the data analysis.
Declaration of interest The authors report no conflicts of interest. This study is supported by grant no. DOH 99M4080 and DOH102-TD-M-113-102002 from the Department of Health, Executive Yuan, Taiwan.
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Appendix Appendix 1. Impact of movement weakness of each joint as part of muscle power impairment. Joint movement power Joint location Shoulder, elbow, hip or knee Wrist or ankle Thumb Index finger Middle, ring or little finger
Paralyzed 8 4 3 2 1
points points points points point
Cannot move against gravity 4 2 0 0 0
points points point point point
Can move against gravity 0 0 0 0 0
point point point point point
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RESEARCH PAPER
Association between muscle power impairment and WHODAS 2.0 in older adults with physical disability in Taiwan Kwang-Hwa Chang1,2, Hua-Fang Liao3, Chia-Fan Yen4, Ai-Wen Hwang5, Wen-Chou Chi6, Reuben Escorpizo7,8,9, and Tsan-Hon Liou2,10 1
Department of Physical Medicine and Rehabilitation, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan, 2Institute of Injury Prevention & Control, Taipei Medical University, Taipei, Taiwan, 3School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan, 4Department of Public Health, Tzu Chi University, Hualien, Taiwan, 5Graduate Institute of Early Intervention, Chang-Gung University, Kweishan, Taoyuan, Taiwan, 6Department of Information Management, National Chung Cheng University, Jiayi, Taiwan, 7Department of Physical Therapy, Louisiana State University Health Sciences Center, New Orleans, LA, USA, 8ICF Research Branch of the WHO Collaboration Centre for the Family of International Classifications in Germany (DIMDI), Nottwil, Switzerland, 9Swiss Paraplegic Research, Nottwil, Switzerland, and 10Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, Taiwan
Abstract
Keywords
Purpose: To explore the association between muscle power impairment and each World Health Organization Disability Assessment Schedule second edition (WHODAS 2.0) domain score among subjects with physical disability. Methods: Subjects (60 years) with physical disability related to neurological diseases, including 730 subjects with brain disease (BD) and 126 subjects with non-BD, were enrolled from a data bank of persons with disabilities from 1 July 2011 to 29 February 2012. Standardized WHODAS 2.0 scores ranging from 0 (least difficulty) to 100 (greatest difficulty) points were calculated for each domain. Results: More than 50% of subjects with physical disability had the greatest difficulty in household activities and mobility. Muscle power impairment (adjusted odds ratios range among domains, 2.75–376.42, p50.001), age (1.38–4.81, p50.05), and speech impairment (1.94–5.80, p50.05) were associated with BD subjects experiencing the greatest difficulty in most WHODAS 2.0 domains. But a few associated factors were identified for the non-BD group in the study. Conclusions: Although the patterns of difficulty in most daily activities were similar between the BD and non-BD groups, factors associated with the difficulties differed between those two groups. Muscle power impairment, age and speech impairment were important factors associated with difficulties in subjects with BD-related physical disability.
Muscle power functions, older adults, physical disability, WHODAS 2.0 History Received 28 September 2013 Revised 22 June 2014 Accepted 27 June 2014 Published online 15 July 2014
ä Implications for Rehabilitation
Older adults with physical disability often experience difficulties in household activities and mobility. Muscle power impairment is associated with difficulties in daily life in subjects with physical disability related to brain disease. Those subjects with brain disease who had older age, a greater degree of muscle power impairment, and the presence of speech impairment were at higher risk of experiencing difficulties in most daily activities.
Introduction According to estimates by the World Health Organization (WHO), one billion or more people globally are disabled [1]. Disability refers to a person’s activity limitations and participation restrictions. Based on a medical model, disability is related to an illness or health condition [2]. However, as a multidimensional
Address for correspondence: Tsan-Hon Liou, MD, PhD, Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, 291 Jhongjheng Rd., Jhonghe, New Taipei City 235, Taiwan. Tel: +886-2-2249-0088 ext. 1600. Fax: +886-2-2248-0577. E-mail: [email protected]
concept, disability is accompanied by various types and degrees of body function impairment, creating different patterns of difficulty in daily living. Therefore, the combined consideration of an illness and impairment in body functions can offer more comprehensive information on disability [3]. Physical disability is one of the most common disabilities. Of those people with a registered disability in Taiwan, 35% have a physical disability [4]. In addition to activity limitations and participation restrictions, persons with physical disability often experience psychological distress [5,6]. The difficulty in daily life increases further if a person has both physical and psychological disorders [7]. The WHO Disability Assessment Schedule second edition (WHODAS 2.0) can offer comprehensive information for
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people with physical disabilities because of its psychometric properties [8]. People with neurological disease-related physical disability may result from either brain disease (BD), such as cerebral stroke, or non-BD, such as spinal cord injury. The impairments in body functions and difficulties in daily life might differ between those two groups because brain plays an important role on cognitive, motor control and speech functions. Most WHODAS 2.0-based studies on people with physical disability have investigated disabilities following a specific illness or health condition [5,6,8–14]. Scant literature has aimed at the extent of the difficulties in daily life for people with different causes of physical disability. Muscle power impairment is a common problem for people with physical disability [15] and can increase their difficulties of daily living [16]. However, few studies have linked impairment in body functions to WHODAS 2.0 domains. We hypothesized that persons with different causes of physical disability have different patterns of difficulty in daily life and that difficulty levels of daily life are associated with impairment degrees of muscle power functions. Therefore, we conducted this study to determine the difficulty level in each WHODAS 2.0 domain and to explore the association between muscle power impairment and each WHODAS 2.0 domain score among persons with physical disability.
Methods The Eligibility Determination System of Disability in Taiwan The rights of people with disabilities are protected by law in Taiwan. Since 1980, each citizen with a sequela or long-term functional impairment after illness can apply for disability evaluation. Within the Eligibility Determination System of Disability in Taiwan, an authorized physician evaluated and reported the applicant’s impairments or problems in body functions and structures using the official Disability Eligibility Determination Scale-version 1980 (DES-1980). DES-1980 has been implemented in Taiwan from 1980 to 2012. Beginning in July 2012, the disability evaluation processes changed under the amended Taiwanese law People with Disabilities Rights Protection Act. Based on the bio-psychosocial model and the International Classification of Functioning, Disability and Health (ICF) framework, the content of the official Disability Eligibility Determination Scale (DES-2012) has changed accordingly [17]. Completing the DES-2012 requires two or more authorized specialists. At least one physician evaluates the subject’s impairments in body functions and structures using the items related to ICF categories. Another interviewer evaluates the subject’s activity limitations and participation restrictions using the 36-item version of WHODAS 2.0 and the ICF categories regarding environmental factors. After training and becoming qualified, a professional specialist in the field of physical therapy, occupational therapy, speech therapy, psychology or social work for 1 year or more is authorized to be an interviewer for the DES-2012. Based on the ICF, WHODAS 2.0 was developed to assess the difficulty in daily activities and social participation experienced by a person in the prior 30 days. The WHODAS 2.0 has six domains. Domain 1, cognition or understanding and communicating (UC), includes six items; Domain 2, mobility, includes five items; Domain 3, self-care, includes four items; Domain 4, getting along with people (GAP), includes five items; Domain 5a, household activities (HA), includes four items; Domain 5b, work and school activities (WA), includes four items; and Domain 6, participation, includes eight items. The WHODAS 2.0 is closely linked to the ICF component d activities and participation [3] and is a reliable and helpful instrument to measure disability [9,18].
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Based on the WHO guidelines and permission, we translated WHODAS 2.0 into traditional Chinese version which was validated by the experts in the field of physical therapy, occupational therapy, psychology, linguistics and rehabilitation. The Taiwan Data bank of Persons with Disability In a pilot study from 2011 to 2012, we used the DES-2012 to assess 6244 individuals nationwide. Compiling the DES-2012 data of those 6244 individuals, we constructed the preliminary part of Taiwan Data bank of Persons with Disability (TDPD). The TDPD consists of each participant’s information, including gender, age, major caregiver, work or school status, area of residence [19], disability-related illnesses or health conditions, major impairment in body functions and structures coded as ICF categories, the scores of each WHODAS 2.0 domain, and overall score. Participants We recruited people who experienced neurological diseaserelated physical disability and had impairment in muscle power functions (ICF category b730) from the preliminary part of TDPD (Figure 1). We excluded those who were in a vegetative state or had dementia from the sample. Based on the primary disabling condition, we divided all participants into BD and non-BD groups. However, aging is an important risk factor for disability [20,21] and an age difference may exist between BD and non-BD groups. Focusing on the effects of muscle power impairment on the difficulties in daily living, we would like to eliminate the age difference from those two groups. Thus, those subjects younger than 60 years were also excluded in the study. Other potential
Figure 1. Summary of the recruitment processes of participants in this study and the participants’ distribution in each domain.
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risk factors for disability, including gender, major caregiver, work or school status, area of residence, disability-related illnesses or health conditions, and major impairment in body functions and structures were collected from the TDPD. Major caregivers included immediate family (parents, children, grandchildren and spouse), extended family (sibling and other relatives), and institution workers or friends. Work or school statuses included employed, housekeeping or retirement, and unemployment. Residence included urban, suburban and rural areas. The Joint Institutional Review Board of Taipei Medical University approved this study.
four impact values were added up. We added 1 point to the sum if the subtotal value of both arms equals the subtotal value of both legs because people with functional impairment of both arm and leg have worse outcome than those with either an arm or leg impairment [24]. Subjects experiencing a sum value of impact ranging from 1 to 3 points were identified as having a minimal degree of muscle power impairment. Conversely, 4–8 points represented mild impairment, 9–22 points represented moderate impairment, and 23–33 points represented severe impairment. The degree of muscle power impairment was coded along with ICF category b730 in the TDPD.
Measurements
Data analysis
An interviewer asked each participant to rate his or her difficulties (without any assistance of persons or devices) in doing each WHODAS 2.0 item using a 5-point Likert scale. On this scale, 5 indicates an activity that was done with extreme difficulty; 4, severe difficulty; 3, moderate difficulty; 2, mild difficulty; and 1, no difficulty. Based on the WHODAS 2.0 manual [22], the participant did not rate those items not experienced in the prior 30 days. Those items not rated were consequently recorded as missing data. The participant might often have extreme difficulty doing those items not experienced in the prior 30 days. Therefore, using the imputation procedure to handle missing data [22] might produce an underestimating bias in this study. We calculated standardized scores of each domain and the 32-item index on the basis of item-response theory and the WHODAS 2.0 manual [22]. Partly because of the participants’ characteristics of being older than 60 years and being physically disabled, only a few participants responded to items in the WA domain. Those items within the WA domain were excluded from the 36-item questionnaire. Therefore, we used the 32-item version instead of the 36-item version to evaluate overall disability in this study. To reduce the underestimating bias, we did not calculate the standardized score of each domain on a subject by subject basis, if any item within the domain had missing data. Likewise, we did not calculate the standardized score of the 32-item index if any item within the index had missing data. Consequently, the amount of data available for analysis decreased (Figure 1). The standardized scores ranged between 0 and 100 points, with higher scores represent more severe disabilities. We dichotomized all subjects and identified those with the greatest difficulty with a standardized score of 100 points in each domain and the 32-item index separately. Based on experts’ consensus, the classification of a person’s physical limitation associated with muscle power impairment was dependent on the grades of joint movement power and the joint location. This classification method was validated by experts and included in both DES-1980 and DES-2012 and has been effectively implemented in the Eligibility Determination System of Disability nationwide in Taiwan for decades. Within this system, an authorized physician evaluates the joint movement power of all weak joints. Each joint has three grades of movement weakness, from being totally paralyzed or having difficult in moving voluntarily or with a manual muscle testing [23] of Grades 0–1, being able to move but not against gravity or with a manual muscle testing of Grade 2, and being able to move against gravity or with a manual muscle testing of Grades 3–4. Because a joint has two or more directions of movement, the weakest power of movement was recorded for each joint. With reference to joint location, we weighed the weakness of each joint’s movement as part of the effect on muscle power impairment of a participant (Appendix). We calculated the sum of the impact values and estimate the degrees of muscle power impairment for each person. When four or more weak joints were evaluated, only the greatest
Using a Pearson Chi-squared test or Fisher’s exact test, we compared differences in clinical characteristics, the distribution of subjects with the greatest difficulty in each domain, and the distribution of subjects requiring assistance for performance for each domain between BD and non-BD groups. Using an independent t-test, we compared age differences between the BD and non-BD groups. Because the standardized scores of the 32-item index and each domain were not normally distributed (Kolmogorov–Smirnov test, p50.05), we used a Mann–Whitney U-test to compare differences in the standardized scores of the 32-item index and each domain between the BD and non-BD groups. We also used Spearman’s rank correlation coefficient (Spearman’s rho) to assess the agreement between the degrees of muscle power impairment and standardized scores of each domain. Spearman’s rho ranged from 0.3 to 0.6 was identified as showing moderate agreement [25]. We used logistic regression analyses with the stepwise method to assess risk factors for subjects with the greatest difficulty in each domain and in the 32-item index. Those variables found to have significant association with domain scores in the univariate analyses were entered into the model for multivariate analyses. The interactions of any two significant variables were also entered for analyses. Based on the results of the multivariate analyses, we estimated the probability of having the greatest difficulty in each domain. Using –2 log likelihood, we tested the goodness-of-fit of each logistic regression model. Using Cronbach’s a, we tested reliability of domain scores in both BD and non-BD groups. Using Cronbach’s a, we tested reliability of domain scores in both BD and non-BD groups. We analyzed data using the Statistical Package for the Social Sciences (version 15.0, SPSS, Chicago, IL), and did not analyze missing data. Therefore, the number of subjects in each domain was not identical (Figure 1). The differences between the groups and the correlations in the groups were considered significant if p values were 50.05. With Bonferroni’s correction for multiple testing, the score difference of each WHODAS 2.0 domain between the groups was considered significant if p values were 50.008.
Results We analyzed 856 subjects with physical disability related to neurological diseases from the preliminary part of TDPD from 1 July 2011 to 29 February 2012. Table 1 shows the basic and clinical characteristics of the participants. Subjects with BD included those with stroke (n ¼ 675), traumatic brain injury (n ¼ 24), brain tumor (n ¼ 10) and other BD (n ¼ 21). Subjects with non-BD included those with spinal cord injury (n ¼ 101) and peripheral nerve disorder (n ¼ 25). Table 2 shows the score distribution in each domain of both BD and non-BD groups. Except for the UC and GAP domains, the patterns of difficulty in other daily activities were similar between those two groups.
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Table 1. Basic and clinical characteristics of subjects with physical disability by brain disease (n ¼ 730) and non-brain disease (n¼126). Variable, unit Age, years Female Degrees of muscle power impairment Minimal Mild Moderate Severe Major caregivera Immediate family Extended family Institution workers or friends Work or school Employed Housekeeping or retirement Unemployment Area of residence [19] Urban Suburban Rural Coexisting impairments Speech impairment, yes Balance control impairment, yes Vision impairment, yes Hearing impairment, yes Need assistance for performance of each WHODAS 2.0 domain Understanding and communicating Mobility Self-care Getting along with people Household activities Work and school activities Participation
Brain disease
Non-brain disease
p Valueb
74.2 ± 8.7 328 (44.9)
74.5 ± 8.7 72 (57.1)
0.80 0.01 0.54
15 376 275 64
(2.1) (51.5) (37.7) (8.8)
3 60 47 16
(2.4) (47.6) (37.3) (12.7) 0.28
399 (85.3) 35 (7.5) 34 (7.3)
70 (92.1) 3 (4.0) 3 (4.0)
8 (1.3) 295 (46.8) 327 (51.9)
1 (0.9) 60 (53.6) 51 (45.5)
328 (45.2) 284 (39.1) 114 (15.7)
58 (46.0) 52 (41.3) 16 (14.8)
0.41
0.68
104 19 3 4
(14.2) (2.6) (0.4) (0.5)
0 2 2 0
266 546 594 222 257 41 360
(36.5) (75.1) (82.0) (30.6) (35.5) (18.1) (49.6)
44 89 101 42 59 5 69
(0.0) (1.6) (1.6) (0.0)
50.001 0.76 0.16 1.00
(34.9) (70.6) (80.2) (33.3) (46.8) (11.4) (55.2)
0.74 0.29 0.61 0.54 0.01 0.28 0.25
All data stated as number (%), except for mean age ± standard deviation. WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition. a Immediate family included parents, children, grandchildren and spouse; extended family included sibling and other relatives. b Using independent t-test for continuous variables and Pearson Chi-squared test or Fisher’s exact test for categorical variables.
With moderate degree of muscle power impairment, the score differences were significant in the domains for UC and GAP, yet indistinctive in mobility between the BD and non-BD groups (Figure 2). Except for the HA domain (Spearman’s rho ¼ 0.269), the scores of all other domains showed moderate agreement with the degrees of muscle power impairment (Spearman’s rho range among domains, 0.321–0.445, p50.001) in the BD group. By contrast, except for the mobility (Spearman’s rho ¼ 0.311, p50.001) and GAP (Spearman’s rho ¼ 0.319, p50.005) domains, most domain scores did not show good agreement with the degrees of muscle power impairment in the non-BD group. Compared to the non-BD group (Spearman’s rho ¼ 0.313, p50.05), the BD group (Spearman’s rho ¼ 0.470, p50.001) showed greater agreement between the degree of muscle power impairment and the 32-item score. Domain scores did not differ significantly between genders, major caregivers, work statuses and different levels of urbanization in the living area. Cronbach’s a of the responded items within each domain ranged 0.91–0.98 in the BD group and 0.90–0.99 in the non-BD group. The results of multivariate analyses showed that age, muscle power impairment and speech impairment were important factors associated with BD subjects experiencing the greatest difficulty in most WHODAS 2.0 domains (Table 3). By contrast, a few variables were identified for the non-BD group in the current study. The combined contribution of age and muscle power impairment to the estimated probability of having the greatest difficulty in each WHODAS 2.0 domain was similar between
BD subjects with (Figure 3) and without speech impairment. Compared to those who had speech impairment (Figure 3), BD subjects who did not have speech impairment experienced lower probability of having the greatest difficulty in each WHODAS 2.0 domain.
Discussion Using the preliminary part of TDPD, this study assessed the capacity of each WHODAS 2.0 domain and the overall 32-item index in older adults with physical disability related to neurological diseases and explored the role of muscle power impairment on the subjects’ difficulty in each domain. To our knowledge, this study is the first WHODAS 2.0 report on people with physical disability related to neurological diseases and muscle power impairments. More than half of the participants experienced difficulties in HA and mobility. Subjects of both BD and non-BD groups had similar patterns of difficulty in most daily activities, except that subjects with BD experienced greater difficulties in UC and GAP. Most domain scores and the 32-item score showed moderate agreement with the degree of muscle power impairment in subjects with BD. Those BD subjects who had older age, a greater degree of muscle power impairment, and the presence of speech impairment were at a higher risk of experiencing the greatest difficulty in most domains of daily activities. However, the association between most domain scores and the variables available in the study for subjects with non-BD was lacking.
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Table 2. Summary report of standardized scores of each WHODAS 2.0 domain in subjects with physical disability related to neurological disease.
WHODAS 2.0 domain
Subjects having the greatest difficulty (%)
Skewness (SE)
(40.0–100.0) (20.0–80.0) (35.0–100.0)
180 (28.8)a 13 (11.61) 193 (26.15)
0.6 (32.8) 0.1 (34.6) 0.5 (33.5)
(81.3–100.0) (81.3–100.0) (81.3–100.0)
387 (60.5) 74 (64.4) 461 (59.10)
1.7 (22.4) 1.8 (28.2) 1.7 (23.4)
(70.0–100.0) (50.0–100.0) (70.0–100.0)
226 (51.6) 37 (46.3) 263 (34.79)
1.4 (29.6) 1.1 (34.7) 1.4 (30.5)
(58.3–100.0) (41.7–100.0) (50.0–100.0)
180 (51.1)a 19 (27.9) 199 (26.78)
1.3 (30.0) 0.6 (37.4) 1.2 (31.8)
(100.0–100.0) (100.0–100.0) (100.0–100.0)
398 (81.6) 77 (73.3) 475 (61.45)
3.5 (18.2) 2.2 (28.6) 3.2 (20.6)
Median (IQR)
Understanding and communicating BD (n ¼ 626) 75.0 Non-BD (n ¼ 112) 55.0 Total (n ¼ 738) 70.0 Mobility BD (n ¼ 640) 100.0 Non-BD (n ¼ 115) 100.0 Total (n ¼ 755) 100.0 Self-care BD (n ¼ 438) 100.0 Non-BD (n ¼ 80) 90 Total (n ¼ 518) 100.0 Getting along with people BD (n ¼ 352) 100.0 Non-BD (n ¼ 68) 75. Total (n ¼ 420) 91.7 Household activities BD (n ¼ 488) 100.0 Non-BD (n ¼ 105) 100.0 Total (n ¼ 593) 100.0 Work and school activities BD (n ¼ 112) 14.285 Non-BD (n ¼ 16) 0.0 Total (n ¼ 128) 0.0 Participation BD (n ¼ 452) 79.2 Non-BD (n ¼ 96) 75.0 Total (n ¼ 548) 79.2 32-item index BD (n ¼ 209) 88.0 Non-BD (n ¼ 43) 83.7 Total (n ¼ 252) 87.0
(0.0–100.0) (0.0–75.0) (0.0–100.0)
41 (36.6) 4 (25.0) 45 (6.06)
0.1 (47.5) 0.8 (43.5) 0.2 (47.1)
(54.2–100.0) (47.9–93.8) (54.2–95.8)
114 (25.2) 19 (19.8) 133 (18.02)
0.8 (25.8) 0.5 (25.1) 0.7 (25.7)
(65.2–98.9) (48.9–93.5) (64.1–98.9)
50 (23.9) 7 (16.3) 57 (7.72)
1.0 (21.6) 0.9 (27.7) 1.1 (22.9)
WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition; BD, subjects with brain disease; Non-BD, subjects with non-brain disease; SE, standard error; IQR, interquartile range; 32-item index, the standardized score of 32 WHODAS 2.0 items. Those items within work and school activities domain were not included in the 32-item index. We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 points (least difficulty) to 100 points (greatest difficulty). a p50.001 (versus non-BD, by Pearson Chi-squared test)
Subjects of both BD and non-BD groups were prone to having the greatest difficulty in the HA and mobility domains, in which more than half of the participants had a domain score of 100. The HA and mobility domains are also the most difficult for persons with physical or sensory disabilities in other countries [13,26–28]. Difficulty in mobility can lead to an unsatisfying life [21,29]. The relationship between mobility scores and the degree of muscle power impairment might be independent of disabling conditions because the score difference in mobility was indistinct between BD and non-BD groups in each degree of muscle power impairment (Figure 2b). In addition, both groups showed moderate agreement between the values of mobility and muscle power impairment. Thus, the degree of muscle power impairment could independently represent the difficulty levels of mobility in this study. Although most of the participants experienced greater difficulty in the HA domain, less than half of the participants received help in performing HA tasks. A possible reason for this discrepancy is that numerous subjects having difficulty in HA could live well without participating in HA in Taiwan. Ethnic or sociocultural features of Chinese society, such as the commonly existing extended family, might partly account for this finding. Most participants lived with immediate or extended family in the study. Chuang et al. [30] stated that most patients with stroke in Taipei were cared for by family members or by a full-time foreign
attendant at home after leaving the acute hospital, and thus, were exempted from participating in HA. The preliminary ICF core set for post-stroke disability assessment developed in Taiwan also excludes any category related to ICF chapters d6 domestic life and d8 major life areas [25]. Whether persons with physical limitations were concerned with the difficulty of HA in Chinese society might require further study. Another reason for this discrepancy could be the lack of resources to assist HA performance. The requirements of persons with a disability may change in accordance with various patterns of daily life. Therefore, being aware of the pattern of difficulties in the different domains of daily living, and searching for the associated factors among people with a disability may be essential for the government to develop pertinent policies and to offer helpful programs to assist people in need. These tasks are the focus of this study. However, the influence of environmental factors on the performance of HA requires further investigation. Previous studies have used either one of the scores of the 12-, 32- or 36-item indexes to assess the overall difficulty of a person in daily life [12–14]. However, the frequencies of subjects having the greatest difficulty in mobility, self-care, GAP and HA domains in this study were considerably higher than the frequency occurring using the 32-item index. Using the 32-item index as a proxy, we excluded a number of subjects who experienced the greatest difficulty in these four domains. The significant
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Figure 2. Mean standardized scores of each WHODAS 2.0 domain with various degrees of muscle power impairment in subjects with BD (thick line) and subjects with non-BD (thin line). We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 point (least difficulty) to 100 points (greatest difficulty). *p50.008, yp50.001 (versus the non-BD group, Mann–Whitney U-test). Abbreviations: BD, brain disease; WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition. Table 3. Summary report of logistic regression analysis of potential risk factors of having the greatest difficulty in each WHODAS 2.0 domain in subjects with physical disability.
WHODAS 2.0 domain For subjects with BD Understanding and communicating Mobility Self-care Getting along with people Household activities Participation 32-item index For subjects with non-BD Understanding and communicating Mobility Self-care Getting along with people Household activities Participation 32-item index
Muscle power impairment 120.64 5.02 3.41 3.73 376.42 2.75 2.97
(8.21–1773.21)c (3.57–7.06)c (2.41–4.81)c (2.52–5.54)c (7.47–18975.35)b (1.96–3.85)c (1.85–4.79)c
– 2.44 (1.29–4.61)b 1.92 (1.01–3.66)a – 2.41 (1.16–4.99)a – –
Age 3.54 1.84 2.01 1.95 4.81 1.38
(1.84–6.82)c (1.48–2.3)c (1.56–2.58)c (1.47–2.59)c (2.24–10.32)c (1.07–1.78)a –
2.02 (1.00–4.08)a 2.17 (1.31–3.62)b – – 1.99 (1.11–3.56)a – –
Speech impairment 3.71 2.4 1.94 5.80
(2.2–6.27)c (1.33–4.32)b (1.04–3.62)a (2.72–12.37)c – – – – – – – – – –
Muscle power impairment Age
Goodness-of-fit statistics
0.63 (0.44–0.89)a – – – 0.52 (0.31–0.87)a – –
604.6 (19.5%)c 678.8 (21.0%)c 494.6 (18.5%)c 381.6 (21.8%)c 400.0 (14.3%)c 462.4 (9.5%)c 207.9 (9.6%)c
– – – – – – –
76.3 (5.1%)a 128.3 (14.4%)c 106.2 (3.9%)a 106.7 (12.4%)c
All data stated as adjusted odds ratio (95% confidence interval) for potential risk factors and 2 log-likelihoodintercept-and-covariates value (change %) for goodness-of-fit statistics, not significant data were not shown. The 2 log-likelihoodintercept-and-covariates change % ¼ [(–2 log-likelihoodintercept-only) (–2 log-likelihoodintercept-and-covariates)] 7 (–2 log-likelihoodintercept-only). Independent variables entered the analyses included age (10 years), muscle power impairment (minimal ¼ 1, mild ¼ 2, moderate ¼ 3, severe ¼ 4), speech impairment (no ¼ 0, yes ¼ 1), and the interactions between variables (including muscle power impairment age, muscle power impairment speech impairment, and speech impairment age) for subjects with BD, and included age, muscle power impairment and muscle power impairment age for subjects with non-BD. The interactions between variables, such as muscle power impairment speech impairment and speech impairment age, did not contribute significantly to any of the models and were not shown. Abbreviations: WHODAS 2.0, World Health Organization Disability Assessment Schedule second edition; BD, brain disease; 32-item index, the standardized score of 32 WHODAS 2.0 items. Those items within work and school activities domain were not included in the 32-item index. We computed the standardized score based on the WHODAS 2.0 manual [22]. The range of scores was from 0 points (least difficulty) to 100 points (greatest difficulty). a p50.05, bp50.008, cp50.001.
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Figure 3. Estimated age- and muscle power impairment-specific probability of having the greatest difficulty in each WHODAS 2.0 domain in subjects with brain disease and having speech impairment. According to the degrees of muscle power impairment (diamond, minimal; square, mild; triangle, moderate; circle, severe), a serial of probability of having the greatest difficulty (standardized score ¼ 100 points) in each WHODAS 2.0 domain with age was estimated. The probability increased with age and greater degrees of muscle power impairment in most domains. The functions of the probability were concave down and increasing for subjects with moderate muscle power impairment and were concave up and increasing for subjects with minimal muscle power impairment in most domains.
differences in the rate of subjects having the greatest difficulty in the UC and GAP domains between BD and non-BD groups did not occur with the 32-item index. In addition, we included only one variable, muscle power impairment, in the optimal model to predict BD subjects having the greatest difficulty in the 32-item index. Only subjects with the most difficulty in all six domains could have a 32-item score of 100 points. Therefore, simply using the 32-item score could not uncover the difficulties in certain specific domains of daily living in subjects with physical disabilities. No consensus has been reached in the literature regarding the cut-off point of the WHODAS 2.0 score to identify persons with a substantial disability. Using normative data, Von Korff et al. [31] recommended that people with a WHODAS 2.0 score of 45 points should be considered substantially disabled [31]. However, the scores of our subjects were negatively skewed: More than 75% of our subjects experienced a 32-item score of 45 points. Therefore, we set the highest standardized score of 100 points as the greatest disability for each domain and the 32-item index in this study. Limitations This study explored the role of muscle power impairment on various difficulties in subjects with physical disability. However, this study has three limitations. First, the WHODAS 2.0 scores
showed a prominent ceiling effect in this study. Most participants in this study had a history of a stroke. Gallagher and Mulvany [28] reported that subjects with stroke have a higher 32-item score than subjects with other health conditions. The WHODAS 2.0 scores obtained from the TDPD might be overestimated because persons who are eligible for a disability can receive social welfare services (including a pension) in Taiwan. Second, the reliability of the classification method for assessing muscle power impairmentrelated physical limitation was not well documented although this method has been used by authorized physicians nationwide in Taiwan for decades. Besides, the individual joint movement power was assessed by the aid of manual muscle testing which is reliable [23]. Further study to investigate the reliability and to validate the usefulness of this classification method is needed. Finally, using the existing data from the TDPD, information about the grade of each joint movement power and the major location of impairment in the upper and/or lower extremities was lacking. Information about cognitive functions was also lacking. However, those subjects who were in a vegetative state or had dementia were excluded from the study. Besides, because this is a crosssectional study, we had no data to determine the changes of WHODAS 2.0 scores in response to any long-term changes in certain bio-psycho-social variables among persons with physical disability. Further study with a longitudinal design is needed to assess the changes of WHODAS 2.0 scores and muscle power impairment with time.
DOI: 10.3109/09638288.2014.940428
In conclusion, most subjects with physical disability had difficulties in the HA and mobility domains. Although the patterns of difficulty in most domains of daily life were similar between the BD and non-BD groups, factors associated with difficulties in daily activities were different between those two groups. The standardized scores of WHODAS 2.0 domains and the 32-item showed moderate agreement with the degree of muscle power impairment in subjects with BD. Those subjects with BD who had older age, a more severe degree of muscle power impairment, and the presence of speech impairment were more likely to experience greater difficulty in most domains of daily activities. Simply using the 32-item score could not uncover the difficulties in certain specific domains of daily living in subjects with physical disabilities. The combined consideration of age and impairments in muscle power functions and speech functions can offer more comprehensive information about difficulties in subjects with BD-related physical disability. Other factors not assessed in the current study may contribute to the difficulties in daily activities in subjects with non-BD and need further searching for.
Acknowledgements We thank Chien-Hua Wu, PhD, for his reviewing the statistical methods for the data analysis.
Declaration of interest The authors report no conflicts of interest. This study is supported by grant no. DOH 99M4080 and DOH102-TD-M-113-102002 from the Department of Health, Executive Yuan, Taiwan.
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Appendix Appendix 1. Impact of movement weakness of each joint as part of muscle power impairment. Joint movement power Joint location Shoulder, elbow, hip or knee Wrist or ankle Thumb Index finger Middle, ring or little finger
Paralyzed 8 4 3 2 1
points points points points point
Cannot move against gravity 4 2 0 0 0
points points point point point
Can move against gravity 0 0 0 0 0
point point point point point
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