Prevalence of Dementia-Associated Disability Among Chinese Older Adults: Results from a National Sample Survey Ning Li, Ph.D., Lei Zhang, Ph.D., Wei Du, Ph.D., Lihua Pang, Ph.D., Chao Guo, M.B.B.S., Gong Chen, Ph.D., Xiaoying Zheng, Ph.D.
Objective: Due to rapid population aging and a tidal wave of dementia, dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China and little was known about the magnitude of dysfunction and disability caused by dementia. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults. Methods: We used the second China National Sample Survey on Disability, comprising 2,526,145 persons from 771,797 households. Identiﬁcation for dementia was based on consensus manuals. Standard weighting procedures were used to construct sample weights considering the multistage stratiﬁed cluster sampling survey scheme. Population weighted numbers, weighted prevalence, and the odd ratios (ORs) were calculated. Results: The prevalence rate of dementia-associated disability was 4.64% (95% CI: 4.26e5.01) and it accounted for 41.03% of mental disability among Chinese older adults. Urban residence (OR: 1.33 [1.12e1.57]), older age (80þ years) (OR: 4.12 [3.38e.03]), illiteracy (OR: 1.79 [1.27e2.53]), and currently not married (OR: 1.15 [1.00e1.32]) were associated with increased risk of dementia-associated disability. Compared with those with mental disability of other causes and those with other types of disabilities, older adults with dementia-asscoiated disability were more likely to have severe or extreme difﬁculty in daily activities and social functions. Conclusion: Countermeasures are warranted to obtain a more precise overview of dementia in China, and strategies on enhancing early identiﬁcation, treatment, and rehabilitation should be developed for people with dementia. (Am J Geriatr Psychiatry 2015; 23:320e325) Key Words: Dementia, disability, Chinese population, older adults
ementia, as one of the most common diseases in the older adults,1 affects more than 24.3 million people in the world—and this number will double by
2040.2 The prevalence rates of dementia range from 2.8% to 63.0% in difference regions of the world.3 The prevalence rates are higher among developed
Received March 4, 2014; revised June 3, 2014; accepted June 4, 2014. From the Institute of Population Research, Peking University, China. Send correspondence and reprint requests to Xiaoying Zheng, Ph.D., Institute of Population Research/WHO Collaborating Center on Reproductive Health and Population Science, Peking University, Beijing 100871, China. e-mail: [email protected]
Ning Li and Lei Zhang made equal contributions to this paper. Ó 2015 American Association for Geriatric Psychiatry http://dx.doi.org/10.1016/j.jagp.2014.06.002
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Li et al. regions, but the developing regions have the largest number of people with dementia.2 In 2001, more than 60% of demented people lived in developing countries and this number will rise to 71.2% in 2040.2 There are approximately 6 million people with dementia in developing countries of the west-Paciﬁc region, and these developing countries will experience a rapid growth of dementia (314%e336%) in the next 20 years.2 Dementia results in the loss of cognitive function and is a leading cause of disability among older adults of all races and regions.4 Dementia has become the most important independent contributor to disability for older adults in low- and middle-income countries.5 Dementia contributed 11.2% of years lived with disability in people aged 60 years and older.6 It was estimated that the global societal cost of dementia was US$ 422 million in 2009.7 Dementia brings a huge burden on individuals, families, and societies, and has been established as a major challenge worldwide.8 In China, approximately 5 million people have dementia.2 Prevalence rates of dementia in Chinese older adults range from 1.37% to 8.19%,2,9e15 and there has been a signiﬁcant increase in the prevalence of dementia since 1980s.9 More women are affected by dementia than men,10,13,14 more rural elders have dementia than their urban counterparts,16 and the prevalence of dementia is higher among the oldest old.15 Due to rapid population aging in China17 and the increase of dementia in developing countries worldwide,5,18 dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China, however, and the current literature lacks ﬁndings based on national data. Additionally, little is known about the magnitude of dysfunction and disability caused by dementia in China. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults.
Survey on Disability (CNSSD). This survey was conducted from April 1 to May 31, 2006. The survey used a stratiﬁed, multiphased, and cluster probability sampling. A total of 734 counties (cities or districts), 2,980 towns (townships or streets), and 5,964 communities were selected from 31 provinces, autonomous regions, and municipalities directly under the Central Government in China. The target population of the survey was the non-institutionalized community population, and 2,526,145 persons in 771,797 households were investigated. In this study, information of respondents aged 65 years and older was used. Details of the survey sampling procedures have been described elsewhere.19 Interviewers and Interviewing Procedures
Initially, pre-survey investigation was conducted to determine the number of households, population, and suspected disabled people in the sampling community. After that, face-to-face interviews were conducted to collect information from every family member in the selected households. The CNSSD survey focused on disability and its aim was to describe the prevalence of disability, its associated factors, and the characteristics of people with disabilities in China. Therefore, participants were ﬁrst screened for disabilities, and those suspected to be disabled were then examined and diagnosed by doctors. People with disability caused by dementia were our study subjects in this article (i.e., dementia-associated disability). Approximately 50,000 survey assistants who conducted pre-survey investigation, 20,000 interviewers who conducted the screen scale, as well as 6,000 doctors of various specialties who made the diagnosis of disabilities and their causes participated in the CNSSD survey. During the survey, the diagnosis of disabilities and their causes, treatment, and rehabilitation suggestions, as well as the information of local hospitals and other health facilities, were provided to people diagnosed as disabled. This survey was approved by the State Council of China, and all respondents gave consent to receive the interview and clinical examination.
Data for this study are derived from a national sample survey, the second China National Sample
Demographic information such as age, sex, residence location, education level, marital status, and
Am J Geriatr Psychiatry 23:3, March 2015
Dementia-Associated Disability Among Chinese Elderly family annual income were collected. The deﬁnition and classiﬁcation of disability followed the WHO International Classiﬁcation of Functioning, Disability, and Health.20 In the CNSSD survey, people with mental disability were deﬁned as those who had mental disorders lasting more than one year; which manifested in cognitive, affective, and behavior disorders; and limited and restricted the patients’ daily life and social function.20 Dementia as well as other mental disorders were diagnosed according to the International Statistical Classiﬁcation of Diseases, 10th Revision.21 Mental disability was classiﬁed into four degrees (mild, moderate, severe, and extremely severe) using WHO-DAS II,22 and the six domains (cognition, mobility, self-care, getting along, life activities, and participation) of function in WHO-DAS II were assessed as none, mild, moderate, severe, or extreme difﬁculty. Data Analysis Allowing for the complex sampling design, we used standard weighting procedures calculating the inverse probability of inclusion for an individual survey respondent in the multistage sampling frame.23 Descriptive statistics were used to present the population-weighted numbers and prevalence rates of dementia-associated disability by various demographic characteristics. Multivariable logistic regression models were used to calculate the adjusted odd ratios (ORs) and 95% conﬁdence interval (CI). The Taylor series linearization method was used to estimate variance and its corresponding 95% CI.24 We used the c2 test to examine the difference on proportions of people with severe or extreme difﬁculty in daily activities and social functions among people with dementia-associated disability, people with mental disability of other causes, and people with other disabilities. The procedures SURVEYFREQ and SURVEYLOGISTIC of the SAS 9.1 package were used to perform the data analyses.25 We set p values less than 0.05 as statistically signiﬁcant.
TABLE 1. Prevalence of Dementia-Associated Disability in Chinese Older Adults of the 2006 China National Sample Survey on Disability (CNSSD) Weighted Number Number (N) Sex Male Female Residence location Rural Urban Age range, years 65e69 70e74 75e79 80þ Education level Illiterate Elementary school Junior high school Senior high school and above Marital status Currently not married Currently married Annual family income per capita Higher than national average Equal to or lower than national average Region East Middle West
Weighted Prevalence Rate (%)
3.67 (3.26e4.07) 5.51 (4.97e6.05)
4.45 (3.98e4.92) 5.05 (4.44e5.67)
207 261 299 441
105,293 128,010 145,666 223,765
2.28 3.32 5.80 11.10
(1.92e2.64) (2.84e3.79) (4.99e6.61) (9.72e12.48)
771 291 81 65
403,210 140,155 35,354 24,015
5.81 3.47 3.19 2.63
(5.25e6.37) (2.98e3.96) (2.39e3.98) (1.85e3.41)
6.46 (5.82e7.11) 3.46 (3.09e3.82)
751 184 273
347,086 111,881 143,767
6.38 (5.73e7.04) 2.77 (2.27e3.26) 4.09 (3.34e4.84)
(weighted 130,033,417) were older adults aged 65 years and older. There were 1,208 (weighted 602,734) people with dementia-associated disability and the prevalence rate was 4.64% (95% CI: 4.26e5.01). Dementia-associated disability accounted for 41.03% of mental disability among Chinese older adults (2,846; weighted 1,468,917). As shown in Table 1, prevalence rate of dementia was higher among women (c2 ¼ 46.03, df ¼ 1, p