Hispanic Health Care International, Vol. 11, No. 1, 2013
© 2013 Springer Publishing Company http://dx.doi.org/10.1891/1540-4153.11.1.14
Life-Space Mobility, Perceived Health, and Depression Symptoms in a Sample of Mexican Older Adults Bertha Cecilia Salazar González, PhD, MEd, BNS Universidad Autónoma de Nuevo León, FAEN (School of Nursing), Monterrey, Mexico Leticia Hernández Delgado, MNS, BNS C. Hospital General in Mexico City Juana Edith Cruz Quevedo, BNS, MNS, DNS School of Nursing, Universidad Veracruzana, Veracruz, Mexico Esther C. Gallegos Cabriales, PhD, MA, BNS Universidad Autónoma de Nuevo León, FAEN (School of Nursing), Monterrey, Mexico
Mobility in older adults is essential to preserving their physical independence and health. Changes in mobility are related to cognitive, physical, and emotional factors, among others. We explored symptoms of depression as a mediator variable between chronic diseases and comorbidities and the outcomes of perceived health and life-space mobility in a convenience sample of 135 older Mexican adults. A cross-sectional design was used. Simple and multiple linear regression models were adjusted to verify the assumptions of mediation using Baron and Kenny’s model. Chronic diseases and comorbidities served as independent variables in two separate models, perceived health and life-space mobility served as dependent variables, and depressive symptoms as the mediator variable. Results showed that perceived health and life-space mobility are affected by chronic diseases and comorbidities. However, when symptoms of depression enter the equation, the b coefficients decreased suggesting partial mediation. It is important to assess and treat depression symptoms in older adults rather than assuming that, at their age, depression is normal.
La movilidad en los adultos mayores es esencial para preservar su independencia física y salud. Los cambios en la movilidad se asocian a factores cognitivos, físicos y emocionales, entre otros. Exploramos los síntomas de depresión como variable mediadora entre las enfermedades crónicas y comorbilidades, y la salud percibida y el espacio de movilidad vital, en una muestra por conveniencia de 135 adultos mayores mexicanos. Se uso un diseño transversal. Se ajustaron modelos de regresión simple y múltiple para verificar los supuestos de mediación del modelo de Baron y Kenny. Las enfermedades crónicas y las comorbilidades sirvieron, en dos modelos separados, como variables independientes, la salud percibida y el espacio de movilidad vital como variables dependientes, y los síntomas depresivos como variable mediadora. Los resultados mostraron que la salud percibida y el espacio de movilidad vital son afectados por las enfermedades crónicas y comorbilidades; sin embargo al introducir síntomas depresivos a la ecuación los coeficientes b disminuyeron, sugiriendo mediación parcial. Es importante valorar y tratar los síntomas de depresión en los adultos mayores y no dar por sentado que a su edad son normales.
Keywords: chronic diseases; life-space mobility; perceived health; older adults
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Life-Space Mobility in Mexican Older Adults
M
obility is a complex functional ability associated with various activity domains (physical, cognitive, and sensory, among others) of a person (Stalvey, Owsley, Sloane, & Ball, 1999). In the older adults, mobility is essential to performing daily activities and maintaining independence, social roles, and life plans. Limitations in mobility, in addition to affecting health, autonomy (Lam & Lauder, 2000; Scocco, Fantoni, & Caon, 2005), and self-esteem, are associated with dependence on family members or equipment for movement that in turn may isolate the individual from society. At the household level, dependent family members may demand adaptations from other family members to compensate their limitations or require day care centers, nursing homes, or long-term facilities. Assessment of life-space mobility represents the functional capacity of the older adults to move or walk in the home environment and surrounding geographic areas (neighborhood, city, and beyond). It also determines the degree of independence reflected by functional capacity and health conditions. In this respect, between 8.0% and 10.0% of the population of older Mexican adults suffer from a chronic disease (Castillo, 2006), including comorbidities or geriatric syndromes that can in turn affect functionality. Chronic diseases are associated with decreased mobility in the older adults (Allman, Sawyer-Baker, Maisiak, Sims, & Roseman, 2004); as mentioned, mobility is essential to maintaining social roles and occupational tasks (Frank & Patla, 2003). Conditions that hinder mobility include complications from type 2 diabetes such as neuropathy causing disruption in proprioception and loss of vision, atherosclerosis causing systolic hypertension, and dyspnea and pain caused by cardiovascular disorders (Gupta & Suri, 2002). Complications often occur over time as the disease worsens because patients do not adhere to treatment. In the case of patients with type 2 diabetes, Hernández-Ronquillo, Téllez-Zenteno, Garduño-Espinosa, and González-Acevez (2003) found a high lack of compliance regarding diet (62.0%), exercise (85.0%), and diabetic treatment (17.0%). Comorbidities not only refer to the presence of two or more morbid processes but, similar to geriatric syndromes, also refer to multifactorial clinical conditions that comprise signs and symptoms not fitting the diagnostic criteria of known or well-established diseases (Abizanda-Soler, Paterna-Mellinas, Martínez-Sánchez, & López-Jiménez, 2010; Inouye, Studenski, Tinetti, & Kuchel, 2008). Geriatric syndromes result from a series of processes and body changes caused by the accumulation of alterations in different organs with multifactorial etiologies. Some signs and symptoms are not specific to a particular disease but may be indicative of several. Some comorbidities and geriatric syndromes have common signs and symptoms or may be risk factors for other geriatric syndromes. Inouye et al. (2008) concluded
that some geriatric syndromes, including pressure ulcers, incontinence, falls, functional decline, and delirium, share causes such as older age, functional impairment, cognitive impairment, and a decline in mobility. It is difficult to determine when a risk factor such as impaired mobility causes a geriatric syndrome called functional decline, or remains as a comorbidity, defined as dysfunctional disorders (Abizanda-Soler et al., 2010; Karlamangla et al., 2007). For the purposes of this study, we will use the term comorbidity to describe impaired mobility. Studies in different samples indicate that scores in life-space mobility are negatively related to age and comorbidities (Peel et al., 2005). Ávila-Funes, Melano-Carranza, Payette, and Amieva (2007) showed in a follow-up study that depressive symptoms increase the risk of dependence in instrumental activities of daily living, including shopping, which presupposes minimal movement in the immediate neighborhood. In contrast, inactivity (not leaving the home) is a moderate risk factor (odds ratio [OR] 5 2.35, 95%, confidence interval [CI] 5 1.56– 3.53, p 5 .0001) for the onset of symptoms of depression (Castro-Lizárraga, Ramirez-Zamora, Aguilar-Morales, & Díaz-de Anda, 2006) and for a decrease in space mobility scores (Peel et al., 2005). As a consequence, older adults are socially isolated in a gradual way, favoring functional dependence and social disability. In addition to this, depression negatively affects quality of life (Lam & Lauder, 2000; Scocco et al., 2005). Depression has been proposed as a mediator within several causal pathways such as those between disease, drugs, and mortality (Brenes et al., 2007); economic pressures on mothers and behavior problems among their children (Dennis, Parke, Coltrane, Blacher, & Borthwick-Duffy, 2003); and justice procedures and the perception of abuse by subordinates (Tepper, Duffy, Henle, & Lambert, 2006). It is unknown whether depressive symptoms mediate pathways between chronic diseases, comorbidities, and perceived health and life-space mobility among older adults. The aim of this study was to explore the mediating effect of the presence of symptoms of depression among chronic diseases, comorbidities, and perceived health and life-space mobility in older adults. A mediator variable is a third variable that affects the relationship between a predictive variable (chronic diseases and comorbidities) and an outcome variable (Baron & Kenny, 1984), in this case, perceived health and life-space mobility.
Methods Sample We selected 135 adults older than 60 years of age of both sexes who attended the outpatient geriatric clinic of a tertiary care public hospital in the state of Nuevo León
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Salazar González et al.
“no” responses was used (Sheikh & Yesavage, 1986). If the participant’s response corresponds to the predetermined pattern, a score of 0 is assigned; otherwise a score of 1 point is assigned. Scores of 0–4 are considered normal, 5–10 are deemed moderate depression, and more than 10 are considered severe depression. For this analysis, an index of 0–100 was constructed, where a higher score indicated more depressive symptoms. Cronbach’s alpha coefficient for the GDS in this study was .84. In the personal data chart, age, education, sex, marital status, and main activity were recorded. We also included a checklist asking if the subject was suffering from symptoms or discomfort unrelated to a diagnosed chronic disease registered in the medical record. Responses, such as problems with urination or bowel movements, recent falls, difficulty sleeping, or problems with appetite, were counted as comorbidities. The diagnosed disease(s) were obtained from each participant’s medical record. This study was approved by the ethics and institutional research committees of the School of Nursing, Universidad Autónoma de Nuevo León (UANL) and by the hospital administrators. Recruitment was carried out among patients attending the geriatric clinic. Potential participants were approached and the study described. If the adult agreed to participate, the screening test (MMSE) was conducted. Verification of study inclusion criteria was performed, and if the respondent met the inclusion criteria, informed consent was obtained. Confidentiality, anonymity, and voluntary participation were respected. A follow-up appointment to obtain further study information was scheduled based on the patient’s next appointment with their health professional. All instruments were administered orally by the second author in the nurse’s office.
from June to October 2007. For this study, we required participants to have the ability to move independently or with help, hear an oral interview, and have no cognitive impairment. For the latter criterion, we applied the mini– mental state examination (MMSE). Because we worked with a low-education population, we adjusted the most common MMSE cutoff score of 24 to be 19 in those older adults with 1–4 years of schooling, and 17 for those who were illiterate (Ostrosky-Solís, López-Arango, & Ardila, 1999). We used a descriptive correlational cross-sectional research design.
Measures Perceived health was explored by the health questionnaire SF-12, which is the shortened version of SF-36 (Ware, Kosinski, & Keller, 1996). Both versions have been translated into Spanish and are widely used with different Spanish-speaking people from Latin American countries and Spain (Esquivel-Molina et al., 2009; Hilario-Castillo, Celestino-Soto, Salazar-González, & Cruz-Quevedo, 2010; Vilagut et al., 2005). The SF-12 measures physical, social, emotional, mental, and general health dimensions with 12 questions. To maintain a positive direction in the questionnaire score, we transformed the negative items (1, 9, 10). The raw values were between 12 and 45 points; these were converted into an index of 0–100. A high score reflected better pain-free functioning. The SF-12 questionnaire obtained a Cronbach’s alpha of .87 in this study and .86 in another study of Mexican older adults (HilarioCastillo et al., 2010). The life-space assessment (LSA) questionnaire measures the distance of mobility in older adults (Baker, Bodner, & Allman, 2003). It consists of five questions that examine required mobility assistance in five different locations in the 4 weeks prior to the administration of the questionnaire: (a) within the home and outside the bedroom; (b) in the garage, patio, or garden; (c) within the neighborhood; (d) outside the neighborhood but within the city or town; and (e) outside the city. The wording included in the LSA questionnaire is linguistically equivalent in English and Spanish. Given that participants live in small properties, the word garden was omitted. Responses to each question have a predetermined score (1–5). The corresponding score is multiplied by the frequency of mobility (1–4) resulting a first product, which is in turn is multiplied by the score assigned according to need of personal assistance (1), equipment (1.5), or no assistance (2). The final products of each level are summed, and scores range from 0 to 120 points. A higher score indicates greater mobility. Score reliability (test–retest) was measured after an interval of 2 months producing a correlation of .86 (95% CI 5 .82 2 .97). To assess the presence of depressive symptoms, the Geriatric Depression Scale (GDS) short version, which consists of 15 questions with predetermined “yes” or
Data Analysis The data were analyzed in SPSS version 15 for Windows. Mediation was verified by simple and multiple linear regression models according to Baron and Kenny (1984) starting with verification of the assumptions: (a) in a first model, the predictive variable is related to the outcome variable; (b) in a second model, the predictive variable is related to the mediator because it assumes that the independent variable causes the mediator, and the mediator affects the outcome variable when introduced together with the predictor; and (c) in a third model, predictive variables and the mediator are entered as independent variables, which should affect the outcome variable; and if the b coefficient in the first model becomes 0, perfect mediation exists. If this coefficient decreases, mediation is partial (James & Brett, 1984). Following Baron and Kenny’s (1984) and Kenny’s (2011) diagram (Figure 1), we built 12 regression models. 16
Life-Space Mobility in Mexican Older Adults M
a
b
c'
X
Y
c
X
Y
X � predictive variables (number of chronic diseases and comorbidities) Y � outcome variables (life-space mobility and perceived health) M � mediator variable (symptoms of depression) a � predictive variable that affects the mediator variable b � mediator variable that affects the outcome variable c � predictive variable that affects the outcome variable c' � effect of predictive variable on the outcome variable is reduced or invalidated by the mediator variable
Figure 1. Kenny’s (2011) mediation diagrams.
Regression Models
Results
To explore whether depression modifies the effect of chronic diseases and comorbidities on perceived health and life-space mobility, simple and multiple linear regression models were built. Following the methodology proposed by Baron and Kenny (1984), perceived health was analyzed as a dependent variable mediated by depression considering comorbidities and chronic diseases—in separate models—as independent variables (Table 2, section A). The first set of regression models showed that the strength of the relationship between comorbidities and perceived health (b 5 2.533, p , .001) decreased after the inclusion of depression in the model (b 5 2.396, p , .001), indicating partial mediation. The variation in perceived health had an R2 5 36.5% (Table 2, section A). The following models considered chronic diseases as independent variables, keeping depression as a possible mediator and perceived health as an outcome variable. The model results confirm partial mediation by depression in the association between chronic diseases and perceived health (reduction of b 5 2.302, p 5 .001 to b 5 2.176, p 5 .025). These data are shown in Table 2, section B. Regression models were also run to explore the effect of independent variables on life-space mobility (the dependent
There were 111 female (82.2%) participants. Sixty-seven (49.6%) reported being married and 50 (37.0%) were widowed. Women reported housework as their main activity (88, 65.2%); few men reported having paid work (11, 8.2%), with most being unemployed (36, 26.6%). Both male and female participants reported some physical or financial dependence on their family (29, 11.0%). The number of illnesses reported in the medical record ranged from 0 to 6. The most common were hypertension (69, 51.1%), type 2 diabetes (37, 27.4%), dyslipidemia (28, 20.7%), and osteoarthritis (20, 14.8%). Comorbidities reported by the participants ranged from 0 to 8 (mean [M] 5 2.92, standard deviation [SD] 5 1.86) with the most frequent being falls (74, 54.8%) and decreased vision (72, 53.3%). Few older individuals reported requiring a family member (1, 0.7%) or equipment (22, 16.3%) to move; the rest reported independence (112, 83.0%). According to scores on the depression scale, 43.7% (59) of the participants were classified as normal, 36.3% (49) had moderate depression, and 20.0% (27) had severe depression. Descriptive data for the core variables are seen in Table 1.
TABLE 1. Descriptive and Distribution Data of Variables of Interest (n 5 135) Variable Age Education
M
SD
Mdn
Minimum Value
Maximum Value
73.07
9.08
73.07
60.00
97.00
2.64
3.66
1.00
0.00
15.00
Comorbidities
2.92
1.86
3.00
0.00
8.00
Mobility space
51.61
22.69
52.00
6.00
112.00
Symptoms of depression
36.14
26.59
33.33
0.00
93.00
Perceived health
62.28
20.34
63.63
12.00
100.00
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Salazar González et al.
TABLE 2. Multiple Linear Regression Models of Comorbidities, Chronic Diseases Over Perceived Health, and Mobility Space Using Symptoms of Depression as a Mediator Step
Variable
B
EE
b
R2
gl
A) Dependent: Perceived Health 1
Comorbidities
25.807**
0.799
2.533**
27.9**
1,133
2
Comorbidities symptoms of depression
24.314**
0.825
2.396**
36.5**
2,132
20.252**
0.058
2.330**
A) Dependent: Life-Space Mobility 1
Comorbidities
23.686**
1.004
2.303**
8.5**
1,133
2
Comorbidities symptoms of depression
22.007 ns
1.052
2.165 ns
17.1ns
2,132
20.283*
0.074
2.332*
B) Dependent: Perceived Health 1
Chronic diseases
20.211**
0.058
2.302**
8.4**
1,133
2
Chronic diseases
20.123*
0.054
2.176*
26.2*
2,132
Symptoms of Depression
20.340**
0.059
2.444**
B) Dependent: Life-Space Mobility 1
Chronic diseases
20.242**
0.064
2.310**
8.9**
1,133
2
Chronic diseases symptoms of depression
20.166*
0.063
2.213*
19.0*
2,132
20.290**
0.069
2.340**
ns 5 nonsignificant. *p , .03. **p , .001. variable). Comorbidities showed an effect on life-space mobility (b 5 2.303, p 5 .001). When depression was introduced into the model, the coefficient was reduced and became nonsignificant (b 5 .165, p . .05; Table 2, section A). Similarly, the b coefficient decreased when chronic diseases and symptoms of depression were both introduced in the model predictive of life-space mobility (b 5 2.310, p 5 .001 to b 5 2.213, p , .03). The coefficient of determination of chronic diseases and symptoms of depression on life-space mobility was 19.0% (Table 2, section B).
Additional Findings Additionally, we examined life-space mobility regarding age, sex, and marital status. The data show that adults aged 60–74 years obtained higher means in mobility than those 75 years and older (t 5 3.55, gl 5 133, p 5 .001); men also have better scores in life-space mobility, although this association was not significant (p 5 .102). Having a partner showed similar means indicating no significant differences (Table 3).
TABLE 3. Life-Space Mobility According to Demographic Data n
M
SD
Mdn
Minimum Value
Maximum Value
60–74
75
55.88
24.07
58.00
6.00
112.00
75 or older
60
46.29
19.77
48.00
10.50
88.00
Male
24
58.39
21.62
60.00
9.00
112.00
Female
111
50.15
22.75
52.00
6.00
112.00
Partner (Yes)
68
52.00
23.22
52.00
6.00
112.00
Partner (No)
67
51.22
22.31
48.00
10.50
90.00
Variable Age
Gender
Marital status
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Life-Space Mobility in Mexican Older Adults
Discussion
mobility and perceived health. The coefficients of determination ranged between 17.0 and 36.5, respectively. Symptoms of depression explained 8.0%–18.0% of the variation in perceived health and life-space mobility models. This confirms, as in other studies, that depression affects the elderly and their life-space mobility. One limitation of this study is that other factors may affect our outcome variables, such as cognitive performance, medication, or social support. The selection of participants in a geriatric clinic implies that they have financial resources and/or family support to attend consultation; therefore, the results should be interpreted with caution because the sample is not representative of all older adults in Mexico.
The most frequent chronic diseases recorded in the medical records were hypertension, type 2 diabetes, and dyslipidemia. The first two diseases plus depression were the most prevalent in national studies (Barrantes-Monje, GarcíaMayo, Gutiérrez-Robledo, & Miguel-Jaimes, 2007; DorantesMendoza, Ávila-Funes, Mejia-Arango, Gutiérrez-Robledo, 2007). Adults older than 75 years of age showed significantly reduced life-space mobility relative to those between 60 and 74 years of age, women, or those without a partner, although the latter association was not significant. The question arises whether these differences are clinically significant (Table 3). In one large sample of older adults, the life-space mobility was significantly higher in men than women (Peel et al., 2005). In this study, although men also showed greater life-space mobility than women, the difference was not significant. In this regard, Peel et al. (2005) noted that older women exhibited more functional impairment, which may preclude mobility, especially outside of the home. Women had a higher prevalence of disease, the most frequent being hypertension, diabetes, and osteoarthritis. These diseases and their treatments can affect mobility by different mechanisms such as fainting, blurred vision, dizziness and unsteadiness, vascular problems, or pain in the lower limbs. The literature reports a positive relationship between being married or having a partner and life-space mobility (Peel et al., 2005; Scocco et al., 2005). It is likely that those who reported having a partner are more encouraged to go out with their partner than those who do not. The mediation model assumptions were met (Baron & Kenny, 1984; James & Brett, 1984). Depression partially mediates the relationship between chronic diseases, comorbidities, and life-space mobility and perceived health. In all cases, the effects of the predictive variables reduced the effect of the symptoms of depression, and one of the models even became nonsignificant. According to the authors Baron and Kenny (1984) and James and Brett (1984), full mediation occurs when the coefficients become zero. Nonsignificance is not sufficient because small coefficients may be significant with large samples and large coefficients may be nonsignificant with small samples. Partial mediation implies that there are other mediating factors and predictive variables that have a direct effect on the outcome variable as well as an indirect effect through the mediator (Barrantes-Monje et al., 2007). According to Baron and Kenny (1984), the effects of variables on behavior are mediated by internal transformation processes as in this case where depression is reduced, but not eliminated, by the effect of the predictive variables. A mediating variable is powerful when it significantly reduces the effect of the predictor, but it does not completely predict the occurrence of the outcome variable. This means that there are other factors that negatively affect life-space
Conclusions Adults older than 75 years of age have more reduced lifespace mobility than those 60–74 years of age. Chronic diseases and comorbidities directly and indirectly affect perceived health and life-space mobility through the presence of symptoms of depression. Exercise programs of moderate intensity have proven to be relatively safe, inexpensive, and have the potential to preserve older adults’ mobility. This allows for the maintenance of social relationships potentially decreasing depression. During the relatively long wait times typical of health care visits in Mexico, nurses could use this time to demonstrate, encourage, and train patients in exercises that preserve or enhance their mobility.
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© 2013 Springer Publishing Company http://dx.doi.org/10.1891/1540-4153.11.1.14
Life-Space Mobility, Perceived Health, and Depression Symptoms in a Sample of Mexican Older Adults Bertha Cecilia Salazar González, PhD, MEd, BNS Universidad Autónoma de Nuevo León, FAEN (School of Nursing), Monterrey, Mexico Leticia Hernández Delgado, MNS, BNS C. Hospital General in Mexico City Juana Edith Cruz Quevedo, BNS, MNS, DNS School of Nursing, Universidad Veracruzana, Veracruz, Mexico Esther C. Gallegos Cabriales, PhD, MA, BNS Universidad Autónoma de Nuevo León, FAEN (School of Nursing), Monterrey, Mexico
Mobility in older adults is essential to preserving their physical independence and health. Changes in mobility are related to cognitive, physical, and emotional factors, among others. We explored symptoms of depression as a mediator variable between chronic diseases and comorbidities and the outcomes of perceived health and life-space mobility in a convenience sample of 135 older Mexican adults. A cross-sectional design was used. Simple and multiple linear regression models were adjusted to verify the assumptions of mediation using Baron and Kenny’s model. Chronic diseases and comorbidities served as independent variables in two separate models, perceived health and life-space mobility served as dependent variables, and depressive symptoms as the mediator variable. Results showed that perceived health and life-space mobility are affected by chronic diseases and comorbidities. However, when symptoms of depression enter the equation, the b coefficients decreased suggesting partial mediation. It is important to assess and treat depression symptoms in older adults rather than assuming that, at their age, depression is normal.
La movilidad en los adultos mayores es esencial para preservar su independencia física y salud. Los cambios en la movilidad se asocian a factores cognitivos, físicos y emocionales, entre otros. Exploramos los síntomas de depresión como variable mediadora entre las enfermedades crónicas y comorbilidades, y la salud percibida y el espacio de movilidad vital, en una muestra por conveniencia de 135 adultos mayores mexicanos. Se uso un diseño transversal. Se ajustaron modelos de regresión simple y múltiple para verificar los supuestos de mediación del modelo de Baron y Kenny. Las enfermedades crónicas y las comorbilidades sirvieron, en dos modelos separados, como variables independientes, la salud percibida y el espacio de movilidad vital como variables dependientes, y los síntomas depresivos como variable mediadora. Los resultados mostraron que la salud percibida y el espacio de movilidad vital son afectados por las enfermedades crónicas y comorbilidades; sin embargo al introducir síntomas depresivos a la ecuación los coeficientes b disminuyeron, sugiriendo mediación parcial. Es importante valorar y tratar los síntomas de depresión en los adultos mayores y no dar por sentado que a su edad son normales.
Keywords: chronic diseases; life-space mobility; perceived health; older adults
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Life-Space Mobility in Mexican Older Adults
M
obility is a complex functional ability associated with various activity domains (physical, cognitive, and sensory, among others) of a person (Stalvey, Owsley, Sloane, & Ball, 1999). In the older adults, mobility is essential to performing daily activities and maintaining independence, social roles, and life plans. Limitations in mobility, in addition to affecting health, autonomy (Lam & Lauder, 2000; Scocco, Fantoni, & Caon, 2005), and self-esteem, are associated with dependence on family members or equipment for movement that in turn may isolate the individual from society. At the household level, dependent family members may demand adaptations from other family members to compensate their limitations or require day care centers, nursing homes, or long-term facilities. Assessment of life-space mobility represents the functional capacity of the older adults to move or walk in the home environment and surrounding geographic areas (neighborhood, city, and beyond). It also determines the degree of independence reflected by functional capacity and health conditions. In this respect, between 8.0% and 10.0% of the population of older Mexican adults suffer from a chronic disease (Castillo, 2006), including comorbidities or geriatric syndromes that can in turn affect functionality. Chronic diseases are associated with decreased mobility in the older adults (Allman, Sawyer-Baker, Maisiak, Sims, & Roseman, 2004); as mentioned, mobility is essential to maintaining social roles and occupational tasks (Frank & Patla, 2003). Conditions that hinder mobility include complications from type 2 diabetes such as neuropathy causing disruption in proprioception and loss of vision, atherosclerosis causing systolic hypertension, and dyspnea and pain caused by cardiovascular disorders (Gupta & Suri, 2002). Complications often occur over time as the disease worsens because patients do not adhere to treatment. In the case of patients with type 2 diabetes, Hernández-Ronquillo, Téllez-Zenteno, Garduño-Espinosa, and González-Acevez (2003) found a high lack of compliance regarding diet (62.0%), exercise (85.0%), and diabetic treatment (17.0%). Comorbidities not only refer to the presence of two or more morbid processes but, similar to geriatric syndromes, also refer to multifactorial clinical conditions that comprise signs and symptoms not fitting the diagnostic criteria of known or well-established diseases (Abizanda-Soler, Paterna-Mellinas, Martínez-Sánchez, & López-Jiménez, 2010; Inouye, Studenski, Tinetti, & Kuchel, 2008). Geriatric syndromes result from a series of processes and body changes caused by the accumulation of alterations in different organs with multifactorial etiologies. Some signs and symptoms are not specific to a particular disease but may be indicative of several. Some comorbidities and geriatric syndromes have common signs and symptoms or may be risk factors for other geriatric syndromes. Inouye et al. (2008) concluded
that some geriatric syndromes, including pressure ulcers, incontinence, falls, functional decline, and delirium, share causes such as older age, functional impairment, cognitive impairment, and a decline in mobility. It is difficult to determine when a risk factor such as impaired mobility causes a geriatric syndrome called functional decline, or remains as a comorbidity, defined as dysfunctional disorders (Abizanda-Soler et al., 2010; Karlamangla et al., 2007). For the purposes of this study, we will use the term comorbidity to describe impaired mobility. Studies in different samples indicate that scores in life-space mobility are negatively related to age and comorbidities (Peel et al., 2005). Ávila-Funes, Melano-Carranza, Payette, and Amieva (2007) showed in a follow-up study that depressive symptoms increase the risk of dependence in instrumental activities of daily living, including shopping, which presupposes minimal movement in the immediate neighborhood. In contrast, inactivity (not leaving the home) is a moderate risk factor (odds ratio [OR] 5 2.35, 95%, confidence interval [CI] 5 1.56– 3.53, p 5 .0001) for the onset of symptoms of depression (Castro-Lizárraga, Ramirez-Zamora, Aguilar-Morales, & Díaz-de Anda, 2006) and for a decrease in space mobility scores (Peel et al., 2005). As a consequence, older adults are socially isolated in a gradual way, favoring functional dependence and social disability. In addition to this, depression negatively affects quality of life (Lam & Lauder, 2000; Scocco et al., 2005). Depression has been proposed as a mediator within several causal pathways such as those between disease, drugs, and mortality (Brenes et al., 2007); economic pressures on mothers and behavior problems among their children (Dennis, Parke, Coltrane, Blacher, & Borthwick-Duffy, 2003); and justice procedures and the perception of abuse by subordinates (Tepper, Duffy, Henle, & Lambert, 2006). It is unknown whether depressive symptoms mediate pathways between chronic diseases, comorbidities, and perceived health and life-space mobility among older adults. The aim of this study was to explore the mediating effect of the presence of symptoms of depression among chronic diseases, comorbidities, and perceived health and life-space mobility in older adults. A mediator variable is a third variable that affects the relationship between a predictive variable (chronic diseases and comorbidities) and an outcome variable (Baron & Kenny, 1984), in this case, perceived health and life-space mobility.
Methods Sample We selected 135 adults older than 60 years of age of both sexes who attended the outpatient geriatric clinic of a tertiary care public hospital in the state of Nuevo León
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Salazar González et al.
“no” responses was used (Sheikh & Yesavage, 1986). If the participant’s response corresponds to the predetermined pattern, a score of 0 is assigned; otherwise a score of 1 point is assigned. Scores of 0–4 are considered normal, 5–10 are deemed moderate depression, and more than 10 are considered severe depression. For this analysis, an index of 0–100 was constructed, where a higher score indicated more depressive symptoms. Cronbach’s alpha coefficient for the GDS in this study was .84. In the personal data chart, age, education, sex, marital status, and main activity were recorded. We also included a checklist asking if the subject was suffering from symptoms or discomfort unrelated to a diagnosed chronic disease registered in the medical record. Responses, such as problems with urination or bowel movements, recent falls, difficulty sleeping, or problems with appetite, were counted as comorbidities. The diagnosed disease(s) were obtained from each participant’s medical record. This study was approved by the ethics and institutional research committees of the School of Nursing, Universidad Autónoma de Nuevo León (UANL) and by the hospital administrators. Recruitment was carried out among patients attending the geriatric clinic. Potential participants were approached and the study described. If the adult agreed to participate, the screening test (MMSE) was conducted. Verification of study inclusion criteria was performed, and if the respondent met the inclusion criteria, informed consent was obtained. Confidentiality, anonymity, and voluntary participation were respected. A follow-up appointment to obtain further study information was scheduled based on the patient’s next appointment with their health professional. All instruments were administered orally by the second author in the nurse’s office.
from June to October 2007. For this study, we required participants to have the ability to move independently or with help, hear an oral interview, and have no cognitive impairment. For the latter criterion, we applied the mini– mental state examination (MMSE). Because we worked with a low-education population, we adjusted the most common MMSE cutoff score of 24 to be 19 in those older adults with 1–4 years of schooling, and 17 for those who were illiterate (Ostrosky-Solís, López-Arango, & Ardila, 1999). We used a descriptive correlational cross-sectional research design.
Measures Perceived health was explored by the health questionnaire SF-12, which is the shortened version of SF-36 (Ware, Kosinski, & Keller, 1996). Both versions have been translated into Spanish and are widely used with different Spanish-speaking people from Latin American countries and Spain (Esquivel-Molina et al., 2009; Hilario-Castillo, Celestino-Soto, Salazar-González, & Cruz-Quevedo, 2010; Vilagut et al., 2005). The SF-12 measures physical, social, emotional, mental, and general health dimensions with 12 questions. To maintain a positive direction in the questionnaire score, we transformed the negative items (1, 9, 10). The raw values were between 12 and 45 points; these were converted into an index of 0–100. A high score reflected better pain-free functioning. The SF-12 questionnaire obtained a Cronbach’s alpha of .87 in this study and .86 in another study of Mexican older adults (HilarioCastillo et al., 2010). The life-space assessment (LSA) questionnaire measures the distance of mobility in older adults (Baker, Bodner, & Allman, 2003). It consists of five questions that examine required mobility assistance in five different locations in the 4 weeks prior to the administration of the questionnaire: (a) within the home and outside the bedroom; (b) in the garage, patio, or garden; (c) within the neighborhood; (d) outside the neighborhood but within the city or town; and (e) outside the city. The wording included in the LSA questionnaire is linguistically equivalent in English and Spanish. Given that participants live in small properties, the word garden was omitted. Responses to each question have a predetermined score (1–5). The corresponding score is multiplied by the frequency of mobility (1–4) resulting a first product, which is in turn is multiplied by the score assigned according to need of personal assistance (1), equipment (1.5), or no assistance (2). The final products of each level are summed, and scores range from 0 to 120 points. A higher score indicates greater mobility. Score reliability (test–retest) was measured after an interval of 2 months producing a correlation of .86 (95% CI 5 .82 2 .97). To assess the presence of depressive symptoms, the Geriatric Depression Scale (GDS) short version, which consists of 15 questions with predetermined “yes” or
Data Analysis The data were analyzed in SPSS version 15 for Windows. Mediation was verified by simple and multiple linear regression models according to Baron and Kenny (1984) starting with verification of the assumptions: (a) in a first model, the predictive variable is related to the outcome variable; (b) in a second model, the predictive variable is related to the mediator because it assumes that the independent variable causes the mediator, and the mediator affects the outcome variable when introduced together with the predictor; and (c) in a third model, predictive variables and the mediator are entered as independent variables, which should affect the outcome variable; and if the b coefficient in the first model becomes 0, perfect mediation exists. If this coefficient decreases, mediation is partial (James & Brett, 1984). Following Baron and Kenny’s (1984) and Kenny’s (2011) diagram (Figure 1), we built 12 regression models. 16
Life-Space Mobility in Mexican Older Adults M
a
b
c'
X
Y
c
X
Y
X � predictive variables (number of chronic diseases and comorbidities) Y � outcome variables (life-space mobility and perceived health) M � mediator variable (symptoms of depression) a � predictive variable that affects the mediator variable b � mediator variable that affects the outcome variable c � predictive variable that affects the outcome variable c' � effect of predictive variable on the outcome variable is reduced or invalidated by the mediator variable
Figure 1. Kenny’s (2011) mediation diagrams.
Regression Models
Results
To explore whether depression modifies the effect of chronic diseases and comorbidities on perceived health and life-space mobility, simple and multiple linear regression models were built. Following the methodology proposed by Baron and Kenny (1984), perceived health was analyzed as a dependent variable mediated by depression considering comorbidities and chronic diseases—in separate models—as independent variables (Table 2, section A). The first set of regression models showed that the strength of the relationship between comorbidities and perceived health (b 5 2.533, p , .001) decreased after the inclusion of depression in the model (b 5 2.396, p , .001), indicating partial mediation. The variation in perceived health had an R2 5 36.5% (Table 2, section A). The following models considered chronic diseases as independent variables, keeping depression as a possible mediator and perceived health as an outcome variable. The model results confirm partial mediation by depression in the association between chronic diseases and perceived health (reduction of b 5 2.302, p 5 .001 to b 5 2.176, p 5 .025). These data are shown in Table 2, section B. Regression models were also run to explore the effect of independent variables on life-space mobility (the dependent
There were 111 female (82.2%) participants. Sixty-seven (49.6%) reported being married and 50 (37.0%) were widowed. Women reported housework as their main activity (88, 65.2%); few men reported having paid work (11, 8.2%), with most being unemployed (36, 26.6%). Both male and female participants reported some physical or financial dependence on their family (29, 11.0%). The number of illnesses reported in the medical record ranged from 0 to 6. The most common were hypertension (69, 51.1%), type 2 diabetes (37, 27.4%), dyslipidemia (28, 20.7%), and osteoarthritis (20, 14.8%). Comorbidities reported by the participants ranged from 0 to 8 (mean [M] 5 2.92, standard deviation [SD] 5 1.86) with the most frequent being falls (74, 54.8%) and decreased vision (72, 53.3%). Few older individuals reported requiring a family member (1, 0.7%) or equipment (22, 16.3%) to move; the rest reported independence (112, 83.0%). According to scores on the depression scale, 43.7% (59) of the participants were classified as normal, 36.3% (49) had moderate depression, and 20.0% (27) had severe depression. Descriptive data for the core variables are seen in Table 1.
TABLE 1. Descriptive and Distribution Data of Variables of Interest (n 5 135) Variable Age Education
M
SD
Mdn
Minimum Value
Maximum Value
73.07
9.08
73.07
60.00
97.00
2.64
3.66
1.00
0.00
15.00
Comorbidities
2.92
1.86
3.00
0.00
8.00
Mobility space
51.61
22.69
52.00
6.00
112.00
Symptoms of depression
36.14
26.59
33.33
0.00
93.00
Perceived health
62.28
20.34
63.63
12.00
100.00
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Salazar González et al.
TABLE 2. Multiple Linear Regression Models of Comorbidities, Chronic Diseases Over Perceived Health, and Mobility Space Using Symptoms of Depression as a Mediator Step
Variable
B
EE
b
R2
gl
A) Dependent: Perceived Health 1
Comorbidities
25.807**
0.799
2.533**
27.9**
1,133
2
Comorbidities symptoms of depression
24.314**
0.825
2.396**
36.5**
2,132
20.252**
0.058
2.330**
A) Dependent: Life-Space Mobility 1
Comorbidities
23.686**
1.004
2.303**
8.5**
1,133
2
Comorbidities symptoms of depression
22.007 ns
1.052
2.165 ns
17.1ns
2,132
20.283*
0.074
2.332*
B) Dependent: Perceived Health 1
Chronic diseases
20.211**
0.058
2.302**
8.4**
1,133
2
Chronic diseases
20.123*
0.054
2.176*
26.2*
2,132
Symptoms of Depression
20.340**
0.059
2.444**
B) Dependent: Life-Space Mobility 1
Chronic diseases
20.242**
0.064
2.310**
8.9**
1,133
2
Chronic diseases symptoms of depression
20.166*
0.063
2.213*
19.0*
2,132
20.290**
0.069
2.340**
ns 5 nonsignificant. *p , .03. **p , .001. variable). Comorbidities showed an effect on life-space mobility (b 5 2.303, p 5 .001). When depression was introduced into the model, the coefficient was reduced and became nonsignificant (b 5 .165, p . .05; Table 2, section A). Similarly, the b coefficient decreased when chronic diseases and symptoms of depression were both introduced in the model predictive of life-space mobility (b 5 2.310, p 5 .001 to b 5 2.213, p , .03). The coefficient of determination of chronic diseases and symptoms of depression on life-space mobility was 19.0% (Table 2, section B).
Additional Findings Additionally, we examined life-space mobility regarding age, sex, and marital status. The data show that adults aged 60–74 years obtained higher means in mobility than those 75 years and older (t 5 3.55, gl 5 133, p 5 .001); men also have better scores in life-space mobility, although this association was not significant (p 5 .102). Having a partner showed similar means indicating no significant differences (Table 3).
TABLE 3. Life-Space Mobility According to Demographic Data n
M
SD
Mdn
Minimum Value
Maximum Value
60–74
75
55.88
24.07
58.00
6.00
112.00
75 or older
60
46.29
19.77
48.00
10.50
88.00
Male
24
58.39
21.62
60.00
9.00
112.00
Female
111
50.15
22.75
52.00
6.00
112.00
Partner (Yes)
68
52.00
23.22
52.00
6.00
112.00
Partner (No)
67
51.22
22.31
48.00
10.50
90.00
Variable Age
Gender
Marital status
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Life-Space Mobility in Mexican Older Adults
Discussion
mobility and perceived health. The coefficients of determination ranged between 17.0 and 36.5, respectively. Symptoms of depression explained 8.0%–18.0% of the variation in perceived health and life-space mobility models. This confirms, as in other studies, that depression affects the elderly and their life-space mobility. One limitation of this study is that other factors may affect our outcome variables, such as cognitive performance, medication, or social support. The selection of participants in a geriatric clinic implies that they have financial resources and/or family support to attend consultation; therefore, the results should be interpreted with caution because the sample is not representative of all older adults in Mexico.
The most frequent chronic diseases recorded in the medical records were hypertension, type 2 diabetes, and dyslipidemia. The first two diseases plus depression were the most prevalent in national studies (Barrantes-Monje, GarcíaMayo, Gutiérrez-Robledo, & Miguel-Jaimes, 2007; DorantesMendoza, Ávila-Funes, Mejia-Arango, Gutiérrez-Robledo, 2007). Adults older than 75 years of age showed significantly reduced life-space mobility relative to those between 60 and 74 years of age, women, or those without a partner, although the latter association was not significant. The question arises whether these differences are clinically significant (Table 3). In one large sample of older adults, the life-space mobility was significantly higher in men than women (Peel et al., 2005). In this study, although men also showed greater life-space mobility than women, the difference was not significant. In this regard, Peel et al. (2005) noted that older women exhibited more functional impairment, which may preclude mobility, especially outside of the home. Women had a higher prevalence of disease, the most frequent being hypertension, diabetes, and osteoarthritis. These diseases and their treatments can affect mobility by different mechanisms such as fainting, blurred vision, dizziness and unsteadiness, vascular problems, or pain in the lower limbs. The literature reports a positive relationship between being married or having a partner and life-space mobility (Peel et al., 2005; Scocco et al., 2005). It is likely that those who reported having a partner are more encouraged to go out with their partner than those who do not. The mediation model assumptions were met (Baron & Kenny, 1984; James & Brett, 1984). Depression partially mediates the relationship between chronic diseases, comorbidities, and life-space mobility and perceived health. In all cases, the effects of the predictive variables reduced the effect of the symptoms of depression, and one of the models even became nonsignificant. According to the authors Baron and Kenny (1984) and James and Brett (1984), full mediation occurs when the coefficients become zero. Nonsignificance is not sufficient because small coefficients may be significant with large samples and large coefficients may be nonsignificant with small samples. Partial mediation implies that there are other mediating factors and predictive variables that have a direct effect on the outcome variable as well as an indirect effect through the mediator (Barrantes-Monje et al., 2007). According to Baron and Kenny (1984), the effects of variables on behavior are mediated by internal transformation processes as in this case where depression is reduced, but not eliminated, by the effect of the predictive variables. A mediating variable is powerful when it significantly reduces the effect of the predictor, but it does not completely predict the occurrence of the outcome variable. This means that there are other factors that negatively affect life-space
Conclusions Adults older than 75 years of age have more reduced lifespace mobility than those 60–74 years of age. Chronic diseases and comorbidities directly and indirectly affect perceived health and life-space mobility through the presence of symptoms of depression. Exercise programs of moderate intensity have proven to be relatively safe, inexpensive, and have the potential to preserve older adults’ mobility. This allows for the maintenance of social relationships potentially decreasing depression. During the relatively long wait times typical of health care visits in Mexico, nurses could use this time to demonstrate, encourage, and train patients in exercises that preserve or enhance their mobility.
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Karlamangla, A., Tinetti, M., Guralnik, J., Studenski, S., Wetle, T., & Reuben, R. (2007). Comorbidity in older adults: Nosology of impairment, diseases, and conditions. Journals of Gerontology: A Biological Science Medicine Science, 62, 296–300. Kenny, D. A. (2011). Mediation. Retrieved from http://davidakenny .net/cm/mediate.htm Lam, C. L. K., & Lauder, I. J. (2000). The impact of chronic diseases on the health-related quality of life (HRQOL) of Chinese patients in primary care. Family Practice, 17(2), 159–166. Ostrosky-Solís, F., López-Arango, G., & Ardila, A. (1999). Influencias de la edad y de la escolaridad en el Examen Breve del estado Mental (Mini-mental State Examination) en una población hispano-hablante. Salud Mental, 22(39), 20–25. Peel, C., Baker, P., Roth, D. L., Brown, C., Bodner, E. V., & Allman, R. M. (2005). Assessing mobility in older adults: The UAB Study of Aging Life—Space Assessment. Physical Therapy, 85(10), 1008–1019. Scocco, P., Fantoni, G., & Caon, F. (2005). Role of depressive and cognitive status in self-reported evaluation of quality of life in older people: comparing proxy and physician perspectives. Age & Ageing Journal, 35, 166–171. Sheikh, J. L., & Yesavage, J. A. (1986). Geriatric Depression Scale (GDS). Recent evidence and development of the shorter version. International Journal of Geriatric Psychiatry, 5, 165–172. Stalvey, B. T., Owsley, C., Sloane, M. E., & Ball, K. (1999). The Life-Space Questionnaire: A measure of the extent of mobility of older adults. Journal of Applied Gerontology, 18, 460–478. Tepper, B. J., Duffy, M. K., Henle, C. A., & Lambert, L. S. (2006). Procedural injustice, victim precipitation, and abusive supervision. Personnel Psychology, 59(1), 101–123. Vilagut, G., Ferrer, M., Rajmil, L., Rebollo, P., Permanyer-Miralda, G., Quintana, J. M. . . . Alonso, J. (2005). El cuestionario de Salud SF-36 español: Una década de experiencia y nuevos desarrollos. Gaceta Sanitaria, 19(2), 135–150. Ware, J., Kosinski, M., & Keller, S. (1996). A 12-Item Short-Form Health Survey: Construction of scales and preliminary tests of reliability and validity. Medical Care, 34(3), 220–233. Correspondence regarding this article should be directed to Bertha Cecilia Salazar González, PhD, MEd, BNS, Universidad Autónoma de Nuevo León, UANL, FAEN, Av. Universidad S/N. Cd. Universitaria, San Nicolas de los Garza, Nuevo León, CP. 66451 México. E-mail: [email protected]
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