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- SUBJECTS AND METHODS
Arthritis is the most commonly reported chronic condition and the leading cause of disability among older adults in the United States (1, 2). The prevalence of arthritis is ∼5% for the adult population and increases to ∼50% for those aged ≥65 years (1, 3). Women have a higher prevalence of arthritis than men (2, 4, 5). The prevalence is similar for non-Hispanic whites and African Americans, and somewhat lower for Asians and Hispanics (3, 6).
Arthritis can lead to immobility and physical inactivity, which in turn are risk factors for disability and mortality (2, 7, 8). Studies have shown that disability is one of the most significant predictors of poor health-related outcomes in older persons (9–11). Older adults with disability also have a higher risk for depression and institutionalization (9, 10, 12). The annual direct cost associated with arthritis is nearly 65 billion dollars (13). The estimated annual costs for caring for disabled older adults is 80 billion dollars in the United States (14).
Several recent studies have suggested that positive affect may reduce functional decline in older adults (15–17). Positive affect entails a sense of emotional well-being and an optimistic attitude toward life (15). High positive affect reflects an individual's emotional relationship with his or her environment, communicating qualities such as happiness, personal satisfaction, optimism, and morale (18, 19). The measurements of positive affect and negative affect have been shown to be relatively independent of each other, and the 2 measures correlate with different personal characteristics (20). Persons in a positive mood are likely to engage in social relationships (21), to be optimistic about their future (22), to cope successfully with stressful situations (23), and to feel in control of their lives (23).
Among older adults, it has been shown that the presence of depressive symptoms is associated with functional decline, increased cognitive impairment, increased health care service utilization, and poorer outcomes (24–26). Depression and its side effects have been studied extensively, but there has been limited research on positive affect and its consequences. Emerging studies have found that increasing positive affect decreases the risk of stroke, coronary heart disease, disability, and functional decline (15, 17, 27, 28). Because arthritis is a major predictor of subsequent functional decline, we were interested in whether a positive affect reduces the risk of functional decline in older adults with arthritis. In this study, we used data from the Hispanic Established Population for the Epidemiological Study of the Elderly (EPESE) to examine the relationship between positive affect and subsequent functional disability in older Mexican Americans with self-reported physician-diagnosed arthritis. We hypothesize that high positive affect would be associated with less incident disability in older Mexican Americans with self-reported physician-diagnosed arthritis.
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- SUBJECTS AND METHODS
Of the 3,050 noninstitutionalized older Mexican Americans interviewed at baseline, 1,084 had been told they had arthritis by a physician. Table 2 presents baseline characteristics of this sample. The average age was 72.8 years and 70.7% of respondents were female. More than half of the sample was currently married and 75.5% had <8 years of formal education. The average number of medical conditions was 1.1 (SD 0.9), 36.7% had a BMI ≥ 30 kg/m2, and 13.6% reported at least 1 ADL limitation. The mean positive affect and negative affect scores were 8.4 (SD 3.4) and 3.9 (SD 4.6), respectively.
Table 2. Baseline characteristics of the sample (n = 1,084)*
|Age, years, mean ± SD||1,084||72.8 ± 6.3|
|Sex, female, %||766||70.7|
|Marital status, married, %||562||51.9|
|Education, years, %|| || |
|Number of medical condition, Mean ± SD||1,084||1.1 ± 0.9|
|BMI ≥30 kg/m2, %||388||35.8|
|Positive affect score, possible range 0–12, mean ± SD||1,084||8.4 ± 3.4|
|Positive affect score, %|| || |
|Negative affect score, possible range 0–21, mean ± SD||1,084||3.9 ± 4.6|
|Negative affect score, %|| || |
|Any ADL limitation, %||1,084||13.6|
Of the 937 subjects who reported no activities of daily living (ADL) limitation at baseline, 697 (74.4 %) remained ADL independent 2 years later, 84 (8.9 %) became ADL dependent, 115 (12.3 %) refused to be reinterviewed or were lost to followup, and 41 (4.4 %) were confirmed dead through Epidemiology Resources Incorporated using the Social Security Administration's Death Master Files and reports from relatives.
Table 3 presents results of a univariate analysis predicting odds of any ADL limitation at followup among subjects who were not disabled at baseline. Subjects in the highest positive affect quartile (odds ratio [OR] 0.97, 95% confidence interval [95% CI] 0.25–0.95) and married (OR 0.63, 95% CI 0.40–0.99) were significantly less likely to report ADL limitations 2 years later. Older age (OR 1.11, 95% CI 1.07–1.15) and number of medical conditions (OR 1.52, 95% CI 1.20–1.93) increased the odds of reporting ADL limitations 2 years later.
Table 3. Univariate analysis predicting odds of any ADL limitation at followup among nondisabled older Mexican Americans with arthritis*
|Independent variables||OR (95% CI) n = 781|
|Positive affect score (0–6)|| |
| 7–9||0.97 (0.56–1.70)|
| 10–11||0.57 (0.26–1.24)|
| 12||0.49 (0.25–0.95)|
|Negative affect score (≥1)||0.94 (0.54–1.65)|
|Age (1 year increase)||1.11 (1.07–1.15)|
|Sex (female)||1.59 (0.92–2.75)|
|Marital status (married)||0.63 (0.40–0.99)|
|Education (≥8 years)||0.69 (0.38–1.23)|
|Number of medical conditions||1.52 (1.20–1.93)|
|BMI (≥30 kg/m2)||1.00 (0.63–1.60)|
Table 4 presents the results of a multivariate analysis predicting odds of any ADL limitation at followup among subjects who were not disabled at baseline, as a function of positive affect score at baseline controlling for demographic variables, number of medical conditions, negative affect, and BMI. There was a significant association between high positive affect (score = 12) and reduced risk of ADL disability 2 years later, controlling for baseline sociodemographic variables, medical conditions, and negative affect (OR 0.46, 95% CI 0.22–0.94). Positive affect was also used as a continuous variable in a logistic regression model and included the variables listed above. Each unit increase in positive affect score at baseline (0–12) was associated with a 9% decreased risk of reporting any ADL limitation (OR 0.91, 95% CI 0.85–0.98).
Table 4. Multivariate analysis predicting odds of any ADL limitation at followup among nondisabled older Mexican Americans with arthritis stratified by sex*
|Independent variable||Total sample OR (95% CI) n = 781||Male OR (95% CI) n = 229||Female OR (95% CI) n = 552|
|Positive affect score|| || || |
| 7–9||0.85 (0.47–1.56)||0.63 (0.20–2.00)||0.94 (0.47–1.88)|
| 10–11||0.45 (0.19–1.02)||0.17 (0.03–0.96)||0.69 (0.27–1.75)|
| 12||0.46 (0.22–0.94)||0.05 (0.01–0.49)||0.73 (0.33–1.62)|
|Negative affect score (≥1)||0.66 (0.35–1.25)||0.42 (0.08–2.23)||0.71 (0.36–1.40)|
|Age (1 year increase)||1.12 (1.07–1.16)||2.14 (0.74–6.13)||2.83 (1.61–4.98)|
|Gender (female)||1.38 (0.75–2.56)||—||—|
|Marital status (married)||1.01 (0.59–1.72)||0.52 (0.16–1.70)||0.96 (0.55–1.70)|
|Education (≥8 years)||0.86 (0.47–1.59)||1.34 (0.42–4.30)||0.65 (0.31–1.34)|
|Number of medical conditions||1.59 (1.24–2.06)||1.36 (0.84–2.20)||1.66 (1.23–2.24)|
|BMI (≥30 kg/m2)||1.23 (0.74–2.04)||0.76 (0.22–2.63)||1.17 (0.67–2.04)|
A number of 2-way interactions were tested for positive affect. The only significant interaction was positive affect by sex (OR 1.17, 95% CI 1.00–1.37). Men who scored in the top 2 quartiles (score ≥ 10) were significantly less likely to report any ADL limitation at followup, controlling for demographic variables, number of medical conditions, negative affect, and BMI. A nonsignificant relationship between positive affect score and ADL disability was observed for women (Table 4).
- Top of page
- SUBJECTS AND METHODS
The objective of this study was to assess the relationship between positive affect and subsequent ADL disability in older Mexican Americans with arthritis. We found that higher scores of positive affect at baseline were associated with a lower incidence of ADL disability 2 years later, controlling for sociodemographic variables, prevalent major medical conditions, and respondents' scores on the negative affect questions of the CES-D scale at baseline.
It is important to note that the effect of positive affect on ADL was independent of negative affect. In fact, controlling for negative affect in the overall sample had little effect on the strength of association of positive affect with ADL incidence. Bradburn and Caplovitz (40) and other investigators (41, 42) have argued that the absence of negative affect is not the same as the presence of positive affect (18). Measures of positive and negative affect have been shown to be weakly correlated with each other (18, 20, 43) and share common correlates, such as physical health.
Individuals with arthritis and high positive affect may reduce their risk of becoming ADL disabled through different mechanisms. First, they may have healthier lifestyles and a better adherence to treatment regimens. Second, positive affect may be a measure of an individual's resilience in the face of stress and capacity to cope with stress. Third, they may be able to cope with environmental or physical stressors that lead to better maintenance of physiologic homeostasis.
Escalante and del Rincon (44, 45) have developed a map of the disablement process in rheumatoid arthritis, where they emphasize the influence of psychosocial factors on the disablement process. Their proposed model provides a framework to study factors that can prevent disability. The model specifies stages at which disabling factors, such as depressive symptoms, stress, self efficacy, and coping, exert their influence on the disability process. This may allow clinicians to broaden their understanding of the disability process. Similarly, previous researchers have demonstrated that high positive affect is a protective factor against functional decline in older populations with myocardial infarction and stroke (15, 27, 28, 46) and is associated with increased survival in older populations (15).
Also, we found an interaction effect between positive affect and sex, with positive affect associated with a larger reduction in risk of ADL dependence in men than in women. Additional studies are needed to replicate our findings that positive affect is more protective against disability in men than in women.
Little is known about factors that allow individuals to maintain positive affect in the face of disabling conditions. More research is needed to examine the role that positive affect plays in the psychological adaptation to disease. It is likely that the ability to maintain high levels of positive affect enables individuals to persevere in the face of obstacles and to recover more rapidly from illness.
Our study has some limitations. First is our reliance on self-reported physician diagnosis of arthritis. This allows for errors by both physicians and subjects. Diagnosing arthritis in the elderly is particularly difficult because virtually all older adults have radiographic evidence of degenerative joint changes. The correlation among symptoms (e.g., pain), signs (e.g., crepitus, swelling, joint instability), and radiographic changes is also poor in those aged 65 years and older, compared with younger populations (47). Thus, the determination of arthritis, particularly in epidemiologic surveys, is always somewhat arbitrary. Second, the association between positive affect and decreased risk of subsequent disability is not necessary causal. It is possible that this association is due to some unmeasured correlate of both. However, this association remained after controlling for relevant factors.
Finally, our measure of positive affect is relatively crude. Because positive affect encompasses such overlapping concepts as happiness, self efficacy, personal growth, optimism, autonomy, and morale, one could argue that it would not be well represented by a 4-item scale (23). However, this scale was relatively robust and an independent predictor of future functional disability.
In summary, our results suggest that a high positive affect is associated with lower incidence of ADL disability among older Mexican Americans with arthritis. These findings provide evidence indicating the importance of promoting and helping older adults maintain a high level of emotional wellbeing. The development of comprehensive programs that include attention of emotional state may aid in preventing disability experienced by older arthritis patients.