- Email: [email protected]
Preserving Health of Alzheimer Caregivers: Impact of a Spouse Caregiver Intervention
Preserving Health of Alzheimer Caregivers: Impact of a Spouse Caregiver Intervention Mary S. Mittelman, Dr.P.H., David L. Roth, Ph.D., Olivio J. Clay, M.A., William E. Haley, Ph.D.
Objective: The objective of this study was to determine the effects of counseling and support on the physical health of caregivers of spouses of people with Alzheimer disease. Methods: A randomized controlled trial, conducted between 1987 and 2006 at an outpatient research clinic in the New York City metropolitan area compared outcomes of psychosocial intervention to usual care. Structured questionnaires were administered at baseline and regular follow-ups. A referred volunteer sample of 406 spouse caregivers of community dwelling patients with Alzheimer disease enrolled over a 9.5-year period. Enhanced counseling and support consisted of six sessions of individual and family counseling, support group participation, and continuous availability of ad-hoc telephone counseling. Indicators of physical health included self-rated health (SRH) of caregivers and the number of reported illnesses. Results: Controlling for baseline SRH (mean: 7.24), intervention group caregivers had significantly better SRH than control group caregivers based upon model predicted mean scores four months after baseline (6.87 versus 7.21), and this significant difference was maintained for two years (6.70 versus 7.01). The effect of the intervention on SRH remained significant after controlling for the effects of patient death, nursing home placement, caregiver depressive symptoms and social support satisfaction. Similar benefits of intervention were found for number of illnesses. Conclusion: Counseling and support preserved SRH in vulnerable caregivers. Enhancing caregivers’ social support, fostering more benign appraisals of stressors, and reducing depressive symptoms may yield indirect health benefits. Psychosocial intervention studies with biological measures of physical health outcomes are warranted. (Am J Geriatr Psychiatry 2007; 15:780–789) Key Words: Alzheimer disease, caregiver, self-rated health, longitudinal randomized trial, psychosocial intervention
S
pouses of people with Alzheimer disease (AD) are generally elderly themselves and particularly vulnerable to the physical health effects of caregiving. Individuals who take on the caregiving role are
generally physically healthier than those who do not.1 However, chronic stressors, such as caring for a relative with AD, increase the risk of health problems, including decreased immune system function-
Received September 21, 2006; revised February 25, 2007; accepted March 5, 2007. From the Department of Psychiatry, New York University School of Medicine, New York, NY (MSM); the Department of Biostatistics, University of Alabama, Birmingham, AL (DLR, OJC); and the School of Aging Studies, University of South Florida, Tampa, FL (WEH). Send correspondence and reprint requests to Mary Mittelman, Dr.P.H., Department of Psychiatry, New York University School of Medicine, 550 First Ave., New York, NY 10016. e-mail: [email protected] © 2007 American Association for Geriatric Psychiatry
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Mittelman et al. ing,2– 4 cardiovascular problems,5,6 and increased physical symptoms over time compared with demographically matched controls.7 Such stressors are associated with both the onset of new illnesses and with accelerated disease progression among those who are already ill.8 The relationship between caregiving and poor physical health is especially strong among older caregivers, dementia caregivers, and spouse caregivers.9 Caregivers who have poor health or a serious health condition are more likely to have difficulty providing care, and to report that their physical health had suffered since becoming a caregiver, than those with better health.10 Moreover, caregivers are at significantly increased risk of ending caregiving when their physical health declines,1 perhaps because they are no longer able to carry out the tasks required. Global self-rated health (SRH) has been included in many population studies and projects focused on caregiving because it is a brief but surprisingly valid measure of health status.11 SRH predicts health care costs,12 clinical risk factors such as mobility limitations, high cholesterol, hypertension, obesity, and biological measures of stress such as cortisol/dehydroepiandrosterone and epinephrine13 and is associated with the risk of specific illnesses, medical conditions, and mortality.14 In one study, SRH was independently associated with increased risk of stroke, after controlling for biomedical risk factors for stroke, contributing to 20% of cases, and could alone explain more than one third of the cases among those who rated their health as bad.15 Such studies suggest that SRH may be a proxy for health-related factors that cannot be readily measured with biomedical indicators. Many studies have shown that poor SRH predicts decline in functioning16 –18 and recovery from illness.19 In a review of 27 studies of SRH and mortality, all but four showed an independent significant effect of SRH; in most of the studies, the odds of mortality associated with the poorest level of SRH compared to the highest level was between 1.5 and 3, even when other known health risk factors are accounted for.11 Data from 20 years of the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study (N⫽6,833) indicate that self-ratings of health are sensitive to declines in physical health, especially those associated with mortality.20 Taken together, the results of these studies make a compelling argument for the value of SRH
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as a physical health outcome measure for a study of the impact of psychosocial intervention. Poor physical health may increase the risk of depressive symptoms in caregivers; a longitudinal study showed that SRH of caregivers of relatives with dementia significantly predicted depressive symptoms five years later, while the converse was not true.21 A more recent longitudinal analysis replicated these findings in the general population of older adults and concluded that the effect of depression on SRH is negligible in comparison to the effect of SRH on depression.22 Thus improving physical health could also reduce the rates of depression among caregivers. Despite the well-documented negative health effects of caregiving, we did not find any randomized controlled trials of caregiver intervention that used SRH of dementia caregivers as an outcome. However, several studies suggested that psychosocial intervention for caregivers could have a positive effect on other measures of physical health such as acute hospitalization,23 stress-induced blood pressure reactivity,24 sleep quality,24 and immune function.25 We have previously reported that the New York University (NYU) Caregiver Intervention leads to longterm improvements in caregiver depressive symptoms,26 social support,27 stress appraisals,28 and delay of nursing home placement.29,30 We hypothesized that the intervention would also improve caregivers’ SRH although it did not focus explicitly on health promotion, because several of these outcomes are associated with SRH. Specifically, social support from family and friends is associated with SRH in older adults31,32 and there are biologically plausible pathways for these effects.33 Highly stressed caregivers are especially prone to adverse health effects and excess risk of mortality.34 We further expected that the intervention’s effect would be long lasting, as counseling and support was available to the caregiver throughout the course of the patient’s illness. We hypothesized that, although the intervention’s effect on health might be partially explained by its effects on depression, social support, and appraisal, the effects on SRH would be significant even after taking into account the known benefits of the intervention on these other outcomes. We selected SRH as the primary dependent measure for analysis for several reasons. First, even with a sample of 406 study subjects, there were not sufficient caregivers with any one disease to provide the statistical power for analysis, whereas all partici-
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Preserving Health of Alzheimer Caregivers pants responded to the SRH questions in our assessment. Second, as noted above, prior research suggests many reasons to examine SRH as an overall indicator of health. We also evaluated the intervention’s effect on the number of reported illnesses.
METHODS
telephone, which we call “ad-hoc counseling,” to help them deal with crises and the changing nature of their relative’s symptoms. Caregivers in the treatment group received all four of these components. Caregivers assigned to the usual care group were given resource information on request, but did not receive individual and family counseling. They were not asked to agree to join support groups, although many did on their own.
Study Design The study included 406 spouse caregivers, recruited over a 9.5-year period between 1987 and 1997. To be eligible, potential participants had to be living with the patient at baseline and they or the patient had to have at least one relative living in the metropolitan area. Caregivers were recruited through the NYU Alzheimer’s Disease Center and referrals from the New York City Chapter of the Alzheimer’s Association, other community organizations, private physicians, and other study participants. This study was approved by the Institutional Board of Review of the NYU School of Medicine. Informed consent was obtained from all participants. We randomly assigned spouse caregivers by lottery to an enhanced treatment or a usual care control group after the baseline assessment was completed. Allocation was concealed from participants and counselors until after the baseline assessment, and was then revealed by the counselors opening a sealed envelope in the caregivers’ presence showing randomization to the treatment or usual care conditions. Participants completed evaluations every four months during the first year and every six months thereafter. The comprehensive assessment used structured questionnaires and rating scales to measure the caregiver’s mental and emotional health and social support. Demographic information about the patient and caregiver was obtained at the baseline assessment. The treatment consisted of four components: 1) two individual counseling sessions tailored to each caregiver’s specific situation; 2) four family counseling sessions with the primary caregiver and family members selected by that caregiver; 3) encouragement of continuous participation in locally available support groups that met weekly, beginning after the four-month follow-up; and 4) the continuous availability of counselors to caregivers and families by
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Variables Used in the Analysis The caregiver’s SRH, the primary outcome of interest for this investigation, was assessed with a questionnaire adapted from the Older Americans Resources and Services Multidimensional Assessment Questionnaire (OARS).35 Caregivers were asked three questions to assess their subjective evaluation of their own health: 1) how would you rate your overall physical health at the present time (on a 4-point scale: poor to excellent); 2) is your health now better, about the same, or worse than it was five years ago (on a 3-point scale: worse/about the same/ better); and 3) how much do your physical health troubles stand in the way of your doing the things you want to do (on a 3-point scale: a great deal/a little [some]/not at all)? The sum of the three questions was used to measure SRH. Possible scores ranged from 3 (least healthy) to 10 (healthiest). A checklist of 26 chronic diseases from the OARS assessment, including arthritis and high blood pressure, was included as a measure of number of caregiver illnesses. This measure did not include any weighting for severity of illness. Group was coded as a dichotomous variable (treatment⫽ 1; usual care ⫽ 0), as was caregiver sex (female caregivers⫽1, male caregivers ⫽0). Two additional dichotomous variables were constructed to indicate whether the patient was in a nursing home rather than in the community (nursing home⫽1, community ⫽ 0) or deceased (deceased⫽1, alive⫽0). Caregiver depressive symptoms were measured with the Geriatric Depression Scale (␣ ⫽0.94), a 30-item questionnaire in a yes/no format that was specially developed for use with the elderly.36 The caregiver’s satisfaction with his or her social support network was measured by the average of three questions from the Social Network Questionnaire,37 each measured on a six-point Likert scale (1⫽very dissatisfied, 6⫽very sat-
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Mittelman et al. isfied) that assessed general satisfaction and satisfaction with assistance and emotional support. Statistical Methods We have modeled SRH as a dynamic trajectory, as suggested by Idler and Benyamini,11 comparing change in health over time in the treatment and control groups. The primary aim of the analyses was to estimate the effectiveness of the intervention in improving caregivers’ SRH taking into account the effects of potential confounders. We confined the analysis for this report to follow-ups conducted during the first three years after enrollment, because our previous reported findings26 suggested that treatment effects could be maintained for approximately three years. Thus, the analyses fit models to data obtained at intake, 4-, 8-, and 12-month follow-ups and every 6 months thereafter. Mixed model growth curve analyses were conducted on the SRH scores using SAS Proc Mixed.38 These growth curve analyses offer many advantages over more traditional repeated measures analyses. Growth curves can be fit for each individual subject based on the amount of data that this person has provided. Consequently, caregivers who discontinued participation before the three-year follow-up assessment could be included in the analyses without imputing data for the missing observations. Variability in the time from baseline to follow-ups was explicitly taken into account by using the actual date of the assessments to calculate the weeks variable used in the models. Additionally, individual variability in rate of change over time was estimated by including a random effect for time. Individual growth curve parameters were modeled as a function of group (treatment versus control) and other predictors of interest. Both linear and logarithmic growth models were examined to determine the model that best fit the observed data. The Akaike Information Criterion (AIC)38 was used to evaluate overall model fit and to select the best-fitting growth pattern (i.e., linear or logarithmic). Restricted maximum likelihood estimation was used for the analysis, and an unstructured covariance structure was specified. In all longitudinal models, SRH growth curves were estimated beginning four months after enrollment, the point in time at which the first follow-up assessment was scheduled to occur. Baseline SRH
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was included as a covariate or predictor of change in SRH longitudinally. Baseline SRH and age were expressed as deviations from the baseline mean for all subjects. We began by estimating a covariate-only reference model in which SRH scores obtained at follow-up were modeled as a function of three time-invariant covariates: the baseline SRH score, caregiver gender and caregiver age at baseline, as well as three timedependent covariates, time since the four-month assessment in weeks, a baseline by time interaction effect, and an age by time interaction effect. We examined five successive models by adding predictors of change in SRH to this covariate-only reference model. In order to gain some understanding of the size of the effect of the intervention on SRH, we calculated the reductions in residual variance left unexplained by each model and proportions of variance accounted for using the procedures described by Singer and Willett.39 In model 1, the effects of treatment were examined by adding intervention group (treatment versus usual care) and the treatment by time interaction effect as predictors. Because time was coded such that the intercept or beginning of the growth curve represents model predicted SRH scores four months after baseline, the main effect for treatment group constitutes a comparison between treatment and control groups 4 months after treatment onset. The interaction effect tests whether the effect of treatment significantly increased or diminished over time. In each of the subsequent models, we added timedependent predictors to the variables in the previous model. In model 2, we added two dummy-coded predictors to indicate whether the patient was in the community, in a nursing home or deceased at the time of each assessment to determine whether these transitions had an effect on caregiver SRH. In addition to the variables in model 2, model 3 includes caregiver depressive symptoms, while model 4 includes caregiver satisfaction with social support. These analyses allowed us to examine the respective effects of depressive symptoms and satisfaction with social support as potential mediators of any intervention effect identified in model 2. Finally, model 5 examines the effect of the intervention, beyond its indirect effect through both depressive symptoms and satisfaction with social support collectively.
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Preserving Health of Alzheimer Caregivers Analyses similar to those described above were also conducted with the secondary outcome, number of illnesses. Among the 406 caregivers who enrolled in the study, 396 (97.5%) completed at least one follow-up assessment that included the three SRH items and the number of illnesses, and were included in all the growth curve analyses. Follow-up information was included, regardless of whether the patient was living in the community, in a nursing home, or was deceased.
RESULTS Psychometric Properties of SRH The internal consistency of SRH (Cronbach alpha) was 0.715. The test–retest reliability (Pearson’s correlation) between baseline and the four-month follow-up was r197 ⫽0.741 (p ⬍0.001) for the treatment group and r195 ⫽0.700 (p ⬍0.001) for the usual care control group. Characteristics of Study Subjects at Baseline There were 203 caregivers in each group at baseline. Among these, four assigned to the treatment group and six assigned to the control group had no follow-up data for one or more of the variables used in these analyses (one caregiver died before participating in the first follow-up, two were too ill to continue, and seven refused before the first follow-up assessment). Demographic characteristics at baseline are presented in Table 1. Despite random assignment, 109 (54.8%) caregivers assigned to the treatment group were female, compared with 129 (65.5%) in the control group. To be sure that our results were not artifacts of this chance inequality, and because women report more health problems than men,40 we included caregiver gender as a covariate in all longitudinal growth analyses. There were no significant baseline differences between the treatment and control groups in SRH, number of illnesses, caregiver age, or satisfaction with social support. The significant difference in number of depressive symptoms at baseline was no longer significant after controlling for the effects of gender (F(1,393)⫽2.36, p⫽0.126).
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TABLE 1. Descriptive Characteristics of the Sample and Study Variables at Baseline Variable
Enhanced Treatment
Usual Care
t (2)
N 199 197 Female caregiver, 109 (54.77) 129 (65.48) 4.73a n (%) Age of caregiver 71.61 (8.64) 71.09 (9.40) 0.58 Self-rated health 7.26 (1.47) 7.23 (1.50) 0.22 Depressive 9.01 (5.75) 10.34 (7.09) ⫺2.06 symptoms Average 4.51 (1.32) 4.41 (1.42) 0.10 satisfaction Number of 1.60 (1.32) 1.50 (1.23) 0.82 illnesses
p Value 0.030 0.565 0.826 0.040 0.477 0.410
Notes: Data are means (SD) unless noted. Four subjects in the treatment group and six subjects in the control group had no follow-up interviews, and were not included in the analyses. The baseline group difference in depressive symptoms was no longer significant after statistically controlling for gender. df ⫽ 394 for all variables except sex. a 2 test, df ⫽ 1.
Longitudinal Growth Curve Analyses For the growth curve analyses of changes over the first three years after randomization, the logarithmic model was found to provide better fit than the linear model as indicated by a lower AIC score for the reference model (logarithmic AIC⫽ 7160.1; linear AIC ⫽7171.3). This means that better fit was obtained when the rate of change in SRH was allowed to gradually decrease over time (the logarithmic model) compared to when this rate of change was constrained to be constant over time (the linear model). The results of the longitudinal analyses predicting change in SRH are displayed in Table 2. In all the models, time is defined as the number of weeks after the four-month follow-up. Model 1 indicated that SRH at baseline was highly predictive of SRH at follow-up. There was an overall decrease in SRH over time after the four-month follow-up for both groups of participants. In addition, there was a significant negative interaction between SRH at baseline and time, indicating that those whose health was worse at baseline had lower rates of decline in health over time, largely due to floor effects. The significant main effect for sex indicates that at the four-month follow-up, female caregivers reported poorer SRH on average than males. There was a significant caregiver age-by-time interaction. The negative valence of the estimate indicated that,
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Mittelman et al.
TABLE 2. Logarithmic Model of Change in Subjective Reported Health from Baseline to Year 3 Variables in Model Model 0 SRH at baseline (centered) Caregiver age (centered) Caregiver sex (female ⫽ 1, male ⫽ 0) Time (weeks after 4-month assessment, logarithmic) SRH at baseline ⫻ time Caregiver age ⫻ time Model 1 SRH at baseline (centered) Caregiver age (centered) Caregiver sex (female ⫽ 1, male ⫽ 0) Time (weeks after 4-month assessment, logarithmic) Group (treatment ⫽ 1, usual care ⫽ 0) SRH at baseline ⫻ time Caregiver age ⫻ time Group ⫻ time Model 2: Effect of patient placed in nursing home and patient deceased in addition to Model 1 Patient in nursing home (nursing home ⫽ 1, remaining home ⫽ 0) Patient deceased (deceased ⫽ 1, alive ⫽ 0) Group Group ⫻ time Model 3: Symptoms of depression in caregiver in addition to Model 1 Depressive symptoms Group Group ⫻ time Model 4: Satisfaction with social support in addition to Model 1 Social support Group Group ⫻ time Model 5: Depressive symptoms and satisfaction with social support in addition to Model 1 Depressive symptoms Satisfaction with social support Group Group ⫻ time
b
SE
t
p
0.772 ⫺0.005 ⫺0.246 ⫺0.265 ⫺0.113 ⫺0.017
0.040 0.007 0.104 0.039 0.027 0.004
19.19 ⫺0.73 ⫺2.37 ⫺6.74 ⫺4.17 ⫺3.74
⬍0.001 0.463 0.018 ⬍0.001 ⬍0.001 ⬍0.001
0.772 ⫺0.005 ⫺0.213 ⫺0.240 0.343 ⫺0.112 ⫺0.016 ⫺0.054
0.040 0.007 0.103 0.056 0.117 0.027 0.004 0.079
19.33 ⫺0.77 ⫺2.06 ⫺4.27 2.93 ⫺4.15 ⫺3.71 ⫺0.68
⬍0.001 0.443 0.039 ⬍0.001 0.003 ⬍0.001 ⬍0.001 0.498
⫺0.101 0.196 0.330 ⫺0.046
0.085 0.129 0.117 0.079
⫺1.18 1.52 2.83 ⫺0.59
0.236 0.128 0.005 0.556
⫺0.066 0.242 ⫺0.061
0.005 0.113 0.076
⫺13.08 2.14 ⫺0.81
⬍0.001 0.032 0.417
0.139 0.255 ⫺0.057
0.025 0.118 0.078
5.49 2.17 ⫺0.72
⬍0.001 0.030 0.470
⫺0.064 0.040 0.221 ⫺0.062
0.005 0.026 0.114 0.076
⫺11.82 1.55 1.94 ⫺0.82
⬍0.001 0.122 0.053 0.413
Notes: Model 0: time df ⫽ 377, all other effects df ⫽ 1,592; Model 1: time df ⫽ 376, all other effects df ⫽ 1,593; Model 2: time df ⫽ 376, all other effects df ⫽ 1,591; Model 3: time df ⫽ 376, all other effects df ⫽ 1,592; Model 4: time df ⫽ 376, all other effects df ⫽ 1,592; Model 5: time df ⫽ 376, all other effects df ⫽ 1,591.
after controlling for the other predictors, older caregivers’ health deteriorated more quickly than younger caregivers’ health. Over and above the effects of these covariates, four months after baseline the caregivers in the treatment group had significantly better SRH than those in the control group. The betas, which are regression coefficients, represent the difference in SRH corresponding to a difference of one unit in the independent or predictor variable. Thus, for example, at the four-month assessment, caregivers in the treatment group (1) were 0.34 units higher on the measure of SRH than caregivers in the usual care group (0), 7.21 versus 6.87, respectively (Table 2). In terms of effect size, this represents a difference of 0.23 SD units (0.34/1.50). The group-by-time interaction effect was not significant.
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Comparisons of the covariate-adjusted least squares means for the two groups indicated that the significant group difference was maintained over the first two years of follow-up (Fig. 1). The group effect gradually decreased from 0.34 units at four months to 0.25 units at two years (t(1593)⫽1.96, p⫽0.05) to 0.23 units at three years (t(1593)⫽1.52, p⫽0.13). Analysis of the residual variance across participants indicated that 3.0% of the variance in SRH that was unexplained by the covariates in the reference model could now be explained by the treatment group effect. In model 2, patient status variables were added to the variables included in model 1. Neither placing the patient in a nursing home nor patient death were significantly associated with caregiver SRH. The addition of patient status did not improve model fit
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Preserving Health of Alzheimer Caregivers
FIGURE 1.
Predicted Self-rated Health Scores from a Logarithmic Model Over the First Three Years of the Intervention, Controlling for Caregiver Sex and Age, Patient Age, and Group-by-time Interactions
(AIC⫽ 7156.4 for model 1 versus 7157.2 for model 2) and did not notably alter the effect of the intervention. In models 3 and 4, we examined the effects on SRH of depressive symptoms and satisfaction with social support respectively. Depressive symptoms had a significant effect on SRH, with more depressive symptoms being associated with worse SRH. The intervention still had a significant effect, albeit smaller, indicating that not all of the intervention’s effect on SRH was due to improvements in caregiver depressive symptoms. Forty-three percent of the residual variance explained by treatment group in model 1 was found to be overlapping with and potentially mediated by changes in depressive symptoms, whereas 57% was not. Model 4 results indicate that satisfaction with social support also explained a significant amount of the variability in SRH, but that the group effect was still significant. Of the residual variance explained by treatment group in model 1, 50% was mediated by social support, whereas 50% was not. In the final model, we entered both depressive symptoms and social support, and the group effect on SRH was no longer significant, nor was the effect of satisfaction with social support, although depressive symptoms were still a significant predictor of SRH. Of the residual variance explained by treatment group in model 1, 53% was mediated by the combination of depressive symptoms and social support and 47% was not.
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It should be noted that, in a subsidiary analysis (not shown), we determined that support group participation was not a significant predictor of change in SRH over time. Change Over Time in Number of Physical Illnesses Reported In a secondary analysis, using the same methods and predictors as were used in model 1 for the analyses of SRH, we examined potential differences between the treatment and control groups in the number of illnesses reported in the three years after enrollment. Paralleling the results of the analyses for SRH, we found a significant difference between the groups beginning at four months (b⫽⫺0.188, t(1594)⫽⫺2.05, p⫽0.040), but no group-by-time interaction. Comparisons of the covariate-adjusted least squares means indicated that the significant group difference was maintained over the first six months of follow-up (b⫽⫺0.158, t(1594)⫽⫺1.96, p⫽0.0498 at six months). There was a significant main effect for time, indicating that both groups reported more illnesses as time went on (b⫽0.098, t(376)⫽2.35, p⫽0.020).
DISCUSSION Our findings suggest that the enhanced support intervention led to significant benefits to caregiver self-
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Mittelman et al. rated health. While both groups showed worsening SRH over time, the treatment group showed less of a decline in the first four months after enrolling in the study, which was when the formal counseling sessions took place. This suggests that there was a delay in the negative health effects of caregiving as a result of intervention. The six individual and family counseling sessions took place in the first four months. In several previous publications, we have shown that the intervention group showed improved caregiver social support compared with controls during the first four months of intervention41 but that differences in caregiver appraisal and depressive symptoms are not significant until the eight-month follow-up.28,29 Thus, we believe that the immediate improvements caregivers experienced in social support after beginning the intervention may have also led to improvements in their perceptions of health, probably because they had more emotional and tangible support from family members. The NYU intervention included family counseling sessions aimed at rallying available family supports to provide more concrete assistance with caregiving and emotional support. Commonly available interventions, such as support groups, do not include components that directly recruit family members to enhance support, which was a key component of our intervention. The relative stability in SRH after caregivers participated in individual and family counseling sessions appears to be a significant secondary benefit of the intervention. While part of the effect of the intervention on SRH was related to improvements in other caregiver outcomes, there was also a direct effect on SRH that could not be explained by any single other beneficial outcome of the intervention. We observed a similar benefit to the number of illnesses reported by caregivers. The intervention appears to be associated with a delay in the decline in physical health that is commonly found with aging and accelerated by caregiving. The finding that a psychosocial intervention, emphasizing enhancement of social support, led to improvements in caregiver health may seem surprising because the intervention did not have an explicit emphasis on exercise, health promotion, vaccination, or other specific health-related behaviors. However, the mediation analyses suggest that improving satisfaction with social support had a health-enhancing effect on family caregivers. Social connectedness has
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long been considered a central aspect of health.42 Although the mechanisms for such effects are not well understood, tangible and emotional assistance from family and friends helps avoid the negative impact of loneliness and social isolation on health.43 A recent longitudinal study of 1,576 elderly individuals found that mean SRH did not decline, even in individuals over age 70 years, until the six-year follow-up.44 In the present study, we found that caregivers in both the treatment and control groups experienced declines in SRH over a three-year period. Previous research has found that caregivers enter the role with better than average health, but once in the role show more rapid deteriorations in health over time than noncaregivers. In our study, while less than 25% of caregivers judged their health as fair or poor at baseline (23.14% in the treatment group, compared to 19.70% in the control group), by the time of the one-year follow-up, poor or fair health was reported by 30.27% in the treatment group and 36.31% of the control group. Thus the proportion of subjects with fair to poor health increased by about 7% in the treatment group, while for controls the increase was about 16.6%—more than twice as large. In addition, it is noteworthy that the oldest caregivers experienced the highest rates of decline in health, which suggests that caregiving adds to the risk of decline in SRH that occurs with advanced age. Recent research suggests that SRH is not just a byproduct of depressive symptoms. In fact, the reverse may be true.22 SRH is a powerful prospective predictor of a number of important health outcomes, including depression and mortality. SRH is a measure that can capture the complex interactions among illnesses and the wide variability of severities, allowing each individual to make a differential weighting of each illness, taking into account the presence or absence of health problems, functioning, positive and negative health behaviors, and health services utilization.45,46 SRH is a particularly meaningful concept in assessing the physical health status of the elderly, many of whom suffer chronic illnesses, as it provides a summary of a large number of variables related to overall physical well-being.47 Our findings are consistent with other research48 showing that interventions that improve depressive symptoms in older adults can also improve health. Our findings are unique, however, in demonstrating that
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Preserving Health of Alzheimer Caregivers these health benefits are apparent even after controlling for the effects of intervention on depression, and in showing that improvements in health are mediated by improvements in social support. While the effects on SRH found in our study are relatively small (3% of longitudinal variance in SRH was explained by the intervention effect), as has also been noted in similar research,48 if it were multiplied by the number of spouse caregivers in the United States today it would be considered a major public health success. Participants in the control group received considerable benefit from the availability of counseling on an as-needed basis. This undoubtedly decreased the apparent differential effect of the intervention. Moreover, the participants in this study were relatively healthy and the intervention might have an even larger effect on more vulnerable older caregivers. Our findings add to a growing literature documenting the benefits of caregiver interventions.49 It has become increasingly apparent that, in order to be maximally effective, these interventions should include a structured component and be provided over a long period of time. These results are consistent with the more general conclusion that physical and mental health are richly intertwined, and that interventions that enhance psychological well-being may improve health through multiple mechanisms including improved self-perceptions, and alterations in the cardiovascular and immune systems.50 The effects of the NYU intervention on SRH suggest promising new directions for research. Selfrated health has limitations in that it is a nonspecific measure and potentially subject to the biases of all
self-reported measures, despite its value at predicting illness and mortality. Our measure of number of illnesses also was not weighted by severity of illness. Future research into the impact of psychosocial interventions for caregivers on specific biological outcomes such as immune function or mortality can help delineate the pathways through which these interventions may affect physical health. Additional studies that, like the NYU study, include a large number of caregivers and have long-term follow-ups are essential to elucidate the mechanisms through which psychosocial interventions improve caregiver well-being. Further research that moves health-enhancing psychosocial intervention into the broader community of caregivers and demonstrates the utility of intervention outside of academic settings51 and with more culturally diverse caregivers is a vital step that deserves attention. Most caregivers still do not have access to psychosocial interventions other than support groups. Counseling and support hold promise as a means of preserving health among vulnerable dementia caregivers who are at risk not only for declining health, but also increased mortality.34 This work was supported by grants from the National Institute of Mental Health (R01 MH 42216), the National Institute on Aging (R01 AG14634), the Alzheimer’s Disease Core Center (P30-AG08051), and the Florida Alzheimer’s Disease Research Center (P50-AG025711 to WEH). The authors thank the NYU Caregiver Counseling staff, Steven Ferris, Ph.D., and the caregivers for their participation.
References 1. McCann JJ, Hebert LE, Bienias JL, et al: Predictors of beginning and ending caregiving during a 3-year period in a biracial community population of older adults. Am J Public Health 2004; 94:1800–1806 2. Kiecolt-Glaser JK, Dura JR, Speicher CE, et al: Spousal caregivers of dementia victims: longitudinal changes in immunity and health. Psychosom Med 1991; 53:345–362 3. Kiecolt-Glaser JK, Marucha PT, Malarkey WB, et al: Slowing of wound healing by psychological stress. Lancet 1995; 346: 1194–1196 4. Kiecolt-Glaser JK, Glaser R, Gravenstein S, et al: Chronic stress alters the immune response to influenza virus vaccine in older adults. Proc Nat Acad Sci 1996; 93:3043–3047 5. King AC, Oka RK, Young DR: Ambulatory blood pressure and heart rate responses to the stress of work and caregiving in older women. J Gerontol 1994; 49:M239–M245 6. Shaw WS, Semple SJ, Ho S, et al: Longitudinal analysis of multiple
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indicators of health decline among spousal caregivers. Ann Behav Med 1997; 19:101–109 7. Roth DL, Haley WE, Owen JE, et al: Latent growth models of the longitudinal effects of dementia caregiving: a comparison of African-American and white family caregivers. Psychol Aging 2001; 16:427–436 8. Vitaliano pp, Zhang J, Scanlan JM: Is caregiving hazardous to one’s physical health? A meta-analysis. Psychol Bull 2003; 129: 946–972 9. Pinquart M, Sorensen S: Differences between caregivers and noncaregivers in psychological health and physical health: a metaanalysis. Psychol Aging 2003; 18:250–267 10. Navaie-Waliser M, Feldman PH, Gould DA, et al: When the caregiver needs care: the plight of vulnerable caregivers. Am J Public Health 2002; 92:409–413 11. Idler EL, Benyamini Y: Self-rated health and mortality: a review of twenty-seven community studies. J Health Soc Behav 1997; 38:21–37
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Mittelman et al. 12. Bierman AS, Bubolz TA, Fisher ES, et al: How well does a single question about health predict the financial health of Medicare managed care plans? Eff Clin Prac 1999; 2:56–62 13. Goldman N, Glei DA, Chang M: The role of clinical risk factors in understanding self-rated health. Ann Epidemiol 2004; 14:49–57 14. DeSalvo KB, Fan VS, McDonell MB, et al: Predicting mortality and healthcare utilization with a single question. Health Serv Res 2005; 40:1234–1246 15. Emmelin M, Weinehall L, Stegmayr B, et al: Self-rated ill-health strengthens the effect of biomedical risk factors in predicting stroke, especially for men—an incident case referent study. J Hypertens 2003; 21:887–896 16. Idler EL, Kasl SV: Self-ratings of health: do they also predict change in functional ability? J Gerontol B Psychol Sci Soc Sci 1995; 50:S344–S353 17. Kaplan GA, Camacho T: Perceived health and mortality: a nineyear follow-up of the human population laboratory cohort. Am J Epidemiol 1983; 117:292–304 18. Mor V, Wilcox V, Rakowski W, et al: Functional transitions among the elderly: patterns, predictors, and related hospital use. Am J Public Health 1994; 84:1274–1280 19. Wilcox VL, Kasl SV, Idler EL: Self-rated health and physical disability in elderly survivors of a major medical event. J Gerontol B Psychol Sci Soc Sci 1996; 51:S96–S104 20. Ferraro KF, Kelley-Moore JA: Self-rated health and mortality among black and white adults: examining the dynamic evaluation thesis. J Gerontol B Psychol Sci Soc Sci 2001; 56:S195–S205 21. O’Rourke N, Cappeliez P, Guindon S: Depressive symptoms and physical health of caregivers of persons with cognitive impairment: analysis of reciprocal effects over time. J Aging Health 2003; 15:688–712 22. Kosloski K, Stull DE, Kercher K, et al: Longitudinal analysis of the reciprocal effects of self-assessed global health and depressive symptoms. J Gerontol 2005; 60B:P296–P303 23. Shelton P, Schraeder C, Dworak D, et al: Caregivers’ utilization of health services: results from the Medicare Alzheimer’s Disease Demonstration, Ill. site. J Am Geriatr Soc 2001; 49:1600–1605 24. King AC, Baumann K, O’Sullivan P, et al: Effects of moderateintensity exercise on physiological, behavioral, and emotional responses to family caregiving: a randomized controlled trial. J Gerontol 2002; 57A:M26–M36 25. Hosaka T, Sugiyama Y: Structured intervention in family caregivers of the demented elderly and changes in their immune function. Psychiatry Clin Neurosci 2003; 57:147–151 26. Mittelman MS, Roth DL, Coon DW, et al: Sustained benefit of supportive intervention for depressive symptoms in Alzheimer’s caregivers. Am J Psychiatry 2004; 161:850–856 27. Roth DR, Mittelman MS, Clay OJ, et al: Changes in social support as mediators of the impact of a psychosocial intervention for spouse caregivers of persons with Alzheimer’s disease. Psychol Aging 2005; 20:634–644 28. Mittelman MS, Roth DL, Haley WE, et al: Effects of a caregiver intervention on negative caregiver appraisals of behavior problems in patients with Alzheimer’s disease: results of a randomized trial. J Gerontol B Psychol Sci Soc Sci 2004; 59B:P27–P34 29. Mittelman MS, Ferris SH, Shulman E, et al: A family intervention to delay nursing home placement of patients with Alzheimer disease: a randomized controlled trial. JAMA 1996; 276:1725–1731 30. Mittelman MS, Haley WE, Clay OJ, et al: Improving caregiver well-being delays nursing home placement of patients with Alzheimer disease. Neurology 2006; 67:1592–1599
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31. DuPertuis LL, Aldwin CM, Bosse R: Does the source of support matter for different health outcomes? Findings from the Normative Aging Study. J Aging Health 2001; 13:494–510 32. Monahan DJ, Hooker K: Health of spouse caregivers of dementia patients: The role of personality and social support. Soc Work 1995; 40:305–314 33. Seeman TE: Health promoting effects of friends and family on health outcomes in older adults. Am J Health Promot 2000; 14:362–370 34. Schulz R, Beach SR: Caregiving as a risk factor for mortality: The Caregiver Health Effects Study. JAMA 1999; 282:2215–2219 35. Duke Center for the Study of Aging and Human Development: Multidimensional Functional Assessment: The OARS Methodology. Durham, NC, Duke University Press, 1978 36. Brink TL, Yesavage JA, Owen L, et al: Screening tests for geriatric depression. Clin Gerontol 1982; 1:37–44 37. Stokes JP, et al: Predicting satisfaction with social support from social network structure. Am J Community Psychol 1983; 11: 141–152 38. Littell RC, Milliken GA, Stroup WW, et al: SAS System for Mixed Models. Cary, NC, SAS Institute, 1996 39. Singer JD, Willett JB: Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence. New York, NY, Oxford University Press, 2003 40. Schulz R, O’Brien AT, Bookwala J, et al: Psychiatric and physical morbidity effects of dementia caregiving: prevalence, correlates, and causes. Gerontologist 1995; 35:771–791 41. Drentea P, Clay OJ, Roth DL, et al: Predictors of improvement in social support: five-year effects of a structured intervention for caregivers of spouses with Alzheimer’s disease. Soc Sci Med 2006; 63:957–967 42. Uchino BN, :(Ed.): Social Support and Physical Health: Understanding the Health Consequences of our Relationships. New Haven, CT, Yale University Press, 2004 43. Cacioppo JT, Hawkley LC, Rickett EM, et al: Sociality, spirituality, and meaning making: Chicago Health, Aging, and Social Relations Study. Rev Gen Psychol 2005; 9:143–155 44. Svedberg P, Gatz M, Lichtenstein P, et al: Self-rated health in a longitudinal perspective: a 9-year follow-up twin study. J Gerontol 2005; 60B:S331–S340 45. Groves RM, Fultz NH, Martin E, : Direct questioning about comprehension in a survey setting, in: Questions about Questions: Inquiries into the Cognitive Bases of Surveys, Vol. 21. New York, NY, Sage Publications, 1992 46. Krause NM, Jay GM: What do global self-rated health items measure? Med Care 1994; 32:930–942 47. Benyamini Y, Leventhal H, Leventhal EA: Self-rated oral health as an independent predictor of self-rated general health, self-esteem and life satisfaction. Soc Sci Med 2004; 59:1109–1116 48. Callahan CM, Kroenke K, Counsell SR, et al: Treatment of depression improves physical functioning in older adults. J Am Geriatr Soc 2005; 53:367–373 49. Pinquart M, Sorensen S: Helping caregivers of persons with dementia: which interventions work and how large are their effects? Int Psychogeriatr 2006; 18:577–595 50. Pressman SD, Cohen S: Does positive affect influence health? Psychol Bull 2005; 131:925–971 51. Teri L, McCurry SM, Logsdon R, et al: Training community consultants to help family members improve dementia care: a randomized controlled trial. Gerontologist 2005; 45:802–811
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Objective: The objective of this study was to determine the effects of counseling and support on the physical health of caregivers of spouses of people with Alzheimer disease. Methods: A randomized controlled trial, conducted between 1987 and 2006 at an outpatient research clinic in the New York City metropolitan area compared outcomes of psychosocial intervention to usual care. Structured questionnaires were administered at baseline and regular follow-ups. A referred volunteer sample of 406 spouse caregivers of community dwelling patients with Alzheimer disease enrolled over a 9.5-year period. Enhanced counseling and support consisted of six sessions of individual and family counseling, support group participation, and continuous availability of ad-hoc telephone counseling. Indicators of physical health included self-rated health (SRH) of caregivers and the number of reported illnesses. Results: Controlling for baseline SRH (mean: 7.24), intervention group caregivers had significantly better SRH than control group caregivers based upon model predicted mean scores four months after baseline (6.87 versus 7.21), and this significant difference was maintained for two years (6.70 versus 7.01). The effect of the intervention on SRH remained significant after controlling for the effects of patient death, nursing home placement, caregiver depressive symptoms and social support satisfaction. Similar benefits of intervention were found for number of illnesses. Conclusion: Counseling and support preserved SRH in vulnerable caregivers. Enhancing caregivers’ social support, fostering more benign appraisals of stressors, and reducing depressive symptoms may yield indirect health benefits. Psychosocial intervention studies with biological measures of physical health outcomes are warranted. (Am J Geriatr Psychiatry 2007; 15:780–789) Key Words: Alzheimer disease, caregiver, self-rated health, longitudinal randomized trial, psychosocial intervention
S
pouses of people with Alzheimer disease (AD) are generally elderly themselves and particularly vulnerable to the physical health effects of caregiving. Individuals who take on the caregiving role are
generally physically healthier than those who do not.1 However, chronic stressors, such as caring for a relative with AD, increase the risk of health problems, including decreased immune system function-
Received September 21, 2006; revised February 25, 2007; accepted March 5, 2007. From the Department of Psychiatry, New York University School of Medicine, New York, NY (MSM); the Department of Biostatistics, University of Alabama, Birmingham, AL (DLR, OJC); and the School of Aging Studies, University of South Florida, Tampa, FL (WEH). Send correspondence and reprint requests to Mary Mittelman, Dr.P.H., Department of Psychiatry, New York University School of Medicine, 550 First Ave., New York, NY 10016. e-mail: [email protected] © 2007 American Association for Geriatric Psychiatry
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Mittelman et al. ing,2– 4 cardiovascular problems,5,6 and increased physical symptoms over time compared with demographically matched controls.7 Such stressors are associated with both the onset of new illnesses and with accelerated disease progression among those who are already ill.8 The relationship between caregiving and poor physical health is especially strong among older caregivers, dementia caregivers, and spouse caregivers.9 Caregivers who have poor health or a serious health condition are more likely to have difficulty providing care, and to report that their physical health had suffered since becoming a caregiver, than those with better health.10 Moreover, caregivers are at significantly increased risk of ending caregiving when their physical health declines,1 perhaps because they are no longer able to carry out the tasks required. Global self-rated health (SRH) has been included in many population studies and projects focused on caregiving because it is a brief but surprisingly valid measure of health status.11 SRH predicts health care costs,12 clinical risk factors such as mobility limitations, high cholesterol, hypertension, obesity, and biological measures of stress such as cortisol/dehydroepiandrosterone and epinephrine13 and is associated with the risk of specific illnesses, medical conditions, and mortality.14 In one study, SRH was independently associated with increased risk of stroke, after controlling for biomedical risk factors for stroke, contributing to 20% of cases, and could alone explain more than one third of the cases among those who rated their health as bad.15 Such studies suggest that SRH may be a proxy for health-related factors that cannot be readily measured with biomedical indicators. Many studies have shown that poor SRH predicts decline in functioning16 –18 and recovery from illness.19 In a review of 27 studies of SRH and mortality, all but four showed an independent significant effect of SRH; in most of the studies, the odds of mortality associated with the poorest level of SRH compared to the highest level was between 1.5 and 3, even when other known health risk factors are accounted for.11 Data from 20 years of the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study (N⫽6,833) indicate that self-ratings of health are sensitive to declines in physical health, especially those associated with mortality.20 Taken together, the results of these studies make a compelling argument for the value of SRH
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as a physical health outcome measure for a study of the impact of psychosocial intervention. Poor physical health may increase the risk of depressive symptoms in caregivers; a longitudinal study showed that SRH of caregivers of relatives with dementia significantly predicted depressive symptoms five years later, while the converse was not true.21 A more recent longitudinal analysis replicated these findings in the general population of older adults and concluded that the effect of depression on SRH is negligible in comparison to the effect of SRH on depression.22 Thus improving physical health could also reduce the rates of depression among caregivers. Despite the well-documented negative health effects of caregiving, we did not find any randomized controlled trials of caregiver intervention that used SRH of dementia caregivers as an outcome. However, several studies suggested that psychosocial intervention for caregivers could have a positive effect on other measures of physical health such as acute hospitalization,23 stress-induced blood pressure reactivity,24 sleep quality,24 and immune function.25 We have previously reported that the New York University (NYU) Caregiver Intervention leads to longterm improvements in caregiver depressive symptoms,26 social support,27 stress appraisals,28 and delay of nursing home placement.29,30 We hypothesized that the intervention would also improve caregivers’ SRH although it did not focus explicitly on health promotion, because several of these outcomes are associated with SRH. Specifically, social support from family and friends is associated with SRH in older adults31,32 and there are biologically plausible pathways for these effects.33 Highly stressed caregivers are especially prone to adverse health effects and excess risk of mortality.34 We further expected that the intervention’s effect would be long lasting, as counseling and support was available to the caregiver throughout the course of the patient’s illness. We hypothesized that, although the intervention’s effect on health might be partially explained by its effects on depression, social support, and appraisal, the effects on SRH would be significant even after taking into account the known benefits of the intervention on these other outcomes. We selected SRH as the primary dependent measure for analysis for several reasons. First, even with a sample of 406 study subjects, there were not sufficient caregivers with any one disease to provide the statistical power for analysis, whereas all partici-
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Preserving Health of Alzheimer Caregivers pants responded to the SRH questions in our assessment. Second, as noted above, prior research suggests many reasons to examine SRH as an overall indicator of health. We also evaluated the intervention’s effect on the number of reported illnesses.
METHODS
telephone, which we call “ad-hoc counseling,” to help them deal with crises and the changing nature of their relative’s symptoms. Caregivers in the treatment group received all four of these components. Caregivers assigned to the usual care group were given resource information on request, but did not receive individual and family counseling. They were not asked to agree to join support groups, although many did on their own.
Study Design The study included 406 spouse caregivers, recruited over a 9.5-year period between 1987 and 1997. To be eligible, potential participants had to be living with the patient at baseline and they or the patient had to have at least one relative living in the metropolitan area. Caregivers were recruited through the NYU Alzheimer’s Disease Center and referrals from the New York City Chapter of the Alzheimer’s Association, other community organizations, private physicians, and other study participants. This study was approved by the Institutional Board of Review of the NYU School of Medicine. Informed consent was obtained from all participants. We randomly assigned spouse caregivers by lottery to an enhanced treatment or a usual care control group after the baseline assessment was completed. Allocation was concealed from participants and counselors until after the baseline assessment, and was then revealed by the counselors opening a sealed envelope in the caregivers’ presence showing randomization to the treatment or usual care conditions. Participants completed evaluations every four months during the first year and every six months thereafter. The comprehensive assessment used structured questionnaires and rating scales to measure the caregiver’s mental and emotional health and social support. Demographic information about the patient and caregiver was obtained at the baseline assessment. The treatment consisted of four components: 1) two individual counseling sessions tailored to each caregiver’s specific situation; 2) four family counseling sessions with the primary caregiver and family members selected by that caregiver; 3) encouragement of continuous participation in locally available support groups that met weekly, beginning after the four-month follow-up; and 4) the continuous availability of counselors to caregivers and families by
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Variables Used in the Analysis The caregiver’s SRH, the primary outcome of interest for this investigation, was assessed with a questionnaire adapted from the Older Americans Resources and Services Multidimensional Assessment Questionnaire (OARS).35 Caregivers were asked three questions to assess their subjective evaluation of their own health: 1) how would you rate your overall physical health at the present time (on a 4-point scale: poor to excellent); 2) is your health now better, about the same, or worse than it was five years ago (on a 3-point scale: worse/about the same/ better); and 3) how much do your physical health troubles stand in the way of your doing the things you want to do (on a 3-point scale: a great deal/a little [some]/not at all)? The sum of the three questions was used to measure SRH. Possible scores ranged from 3 (least healthy) to 10 (healthiest). A checklist of 26 chronic diseases from the OARS assessment, including arthritis and high blood pressure, was included as a measure of number of caregiver illnesses. This measure did not include any weighting for severity of illness. Group was coded as a dichotomous variable (treatment⫽ 1; usual care ⫽ 0), as was caregiver sex (female caregivers⫽1, male caregivers ⫽0). Two additional dichotomous variables were constructed to indicate whether the patient was in a nursing home rather than in the community (nursing home⫽1, community ⫽ 0) or deceased (deceased⫽1, alive⫽0). Caregiver depressive symptoms were measured with the Geriatric Depression Scale (␣ ⫽0.94), a 30-item questionnaire in a yes/no format that was specially developed for use with the elderly.36 The caregiver’s satisfaction with his or her social support network was measured by the average of three questions from the Social Network Questionnaire,37 each measured on a six-point Likert scale (1⫽very dissatisfied, 6⫽very sat-
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Mittelman et al. isfied) that assessed general satisfaction and satisfaction with assistance and emotional support. Statistical Methods We have modeled SRH as a dynamic trajectory, as suggested by Idler and Benyamini,11 comparing change in health over time in the treatment and control groups. The primary aim of the analyses was to estimate the effectiveness of the intervention in improving caregivers’ SRH taking into account the effects of potential confounders. We confined the analysis for this report to follow-ups conducted during the first three years after enrollment, because our previous reported findings26 suggested that treatment effects could be maintained for approximately three years. Thus, the analyses fit models to data obtained at intake, 4-, 8-, and 12-month follow-ups and every 6 months thereafter. Mixed model growth curve analyses were conducted on the SRH scores using SAS Proc Mixed.38 These growth curve analyses offer many advantages over more traditional repeated measures analyses. Growth curves can be fit for each individual subject based on the amount of data that this person has provided. Consequently, caregivers who discontinued participation before the three-year follow-up assessment could be included in the analyses without imputing data for the missing observations. Variability in the time from baseline to follow-ups was explicitly taken into account by using the actual date of the assessments to calculate the weeks variable used in the models. Additionally, individual variability in rate of change over time was estimated by including a random effect for time. Individual growth curve parameters were modeled as a function of group (treatment versus control) and other predictors of interest. Both linear and logarithmic growth models were examined to determine the model that best fit the observed data. The Akaike Information Criterion (AIC)38 was used to evaluate overall model fit and to select the best-fitting growth pattern (i.e., linear or logarithmic). Restricted maximum likelihood estimation was used for the analysis, and an unstructured covariance structure was specified. In all longitudinal models, SRH growth curves were estimated beginning four months after enrollment, the point in time at which the first follow-up assessment was scheduled to occur. Baseline SRH
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was included as a covariate or predictor of change in SRH longitudinally. Baseline SRH and age were expressed as deviations from the baseline mean for all subjects. We began by estimating a covariate-only reference model in which SRH scores obtained at follow-up were modeled as a function of three time-invariant covariates: the baseline SRH score, caregiver gender and caregiver age at baseline, as well as three timedependent covariates, time since the four-month assessment in weeks, a baseline by time interaction effect, and an age by time interaction effect. We examined five successive models by adding predictors of change in SRH to this covariate-only reference model. In order to gain some understanding of the size of the effect of the intervention on SRH, we calculated the reductions in residual variance left unexplained by each model and proportions of variance accounted for using the procedures described by Singer and Willett.39 In model 1, the effects of treatment were examined by adding intervention group (treatment versus usual care) and the treatment by time interaction effect as predictors. Because time was coded such that the intercept or beginning of the growth curve represents model predicted SRH scores four months after baseline, the main effect for treatment group constitutes a comparison between treatment and control groups 4 months after treatment onset. The interaction effect tests whether the effect of treatment significantly increased or diminished over time. In each of the subsequent models, we added timedependent predictors to the variables in the previous model. In model 2, we added two dummy-coded predictors to indicate whether the patient was in the community, in a nursing home or deceased at the time of each assessment to determine whether these transitions had an effect on caregiver SRH. In addition to the variables in model 2, model 3 includes caregiver depressive symptoms, while model 4 includes caregiver satisfaction with social support. These analyses allowed us to examine the respective effects of depressive symptoms and satisfaction with social support as potential mediators of any intervention effect identified in model 2. Finally, model 5 examines the effect of the intervention, beyond its indirect effect through both depressive symptoms and satisfaction with social support collectively.
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Preserving Health of Alzheimer Caregivers Analyses similar to those described above were also conducted with the secondary outcome, number of illnesses. Among the 406 caregivers who enrolled in the study, 396 (97.5%) completed at least one follow-up assessment that included the three SRH items and the number of illnesses, and were included in all the growth curve analyses. Follow-up information was included, regardless of whether the patient was living in the community, in a nursing home, or was deceased.
RESULTS Psychometric Properties of SRH The internal consistency of SRH (Cronbach alpha) was 0.715. The test–retest reliability (Pearson’s correlation) between baseline and the four-month follow-up was r197 ⫽0.741 (p ⬍0.001) for the treatment group and r195 ⫽0.700 (p ⬍0.001) for the usual care control group. Characteristics of Study Subjects at Baseline There were 203 caregivers in each group at baseline. Among these, four assigned to the treatment group and six assigned to the control group had no follow-up data for one or more of the variables used in these analyses (one caregiver died before participating in the first follow-up, two were too ill to continue, and seven refused before the first follow-up assessment). Demographic characteristics at baseline are presented in Table 1. Despite random assignment, 109 (54.8%) caregivers assigned to the treatment group were female, compared with 129 (65.5%) in the control group. To be sure that our results were not artifacts of this chance inequality, and because women report more health problems than men,40 we included caregiver gender as a covariate in all longitudinal growth analyses. There were no significant baseline differences between the treatment and control groups in SRH, number of illnesses, caregiver age, or satisfaction with social support. The significant difference in number of depressive symptoms at baseline was no longer significant after controlling for the effects of gender (F(1,393)⫽2.36, p⫽0.126).
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TABLE 1. Descriptive Characteristics of the Sample and Study Variables at Baseline Variable
Enhanced Treatment
Usual Care
t (2)
N 199 197 Female caregiver, 109 (54.77) 129 (65.48) 4.73a n (%) Age of caregiver 71.61 (8.64) 71.09 (9.40) 0.58 Self-rated health 7.26 (1.47) 7.23 (1.50) 0.22 Depressive 9.01 (5.75) 10.34 (7.09) ⫺2.06 symptoms Average 4.51 (1.32) 4.41 (1.42) 0.10 satisfaction Number of 1.60 (1.32) 1.50 (1.23) 0.82 illnesses
p Value 0.030 0.565 0.826 0.040 0.477 0.410
Notes: Data are means (SD) unless noted. Four subjects in the treatment group and six subjects in the control group had no follow-up interviews, and were not included in the analyses. The baseline group difference in depressive symptoms was no longer significant after statistically controlling for gender. df ⫽ 394 for all variables except sex. a 2 test, df ⫽ 1.
Longitudinal Growth Curve Analyses For the growth curve analyses of changes over the first three years after randomization, the logarithmic model was found to provide better fit than the linear model as indicated by a lower AIC score for the reference model (logarithmic AIC⫽ 7160.1; linear AIC ⫽7171.3). This means that better fit was obtained when the rate of change in SRH was allowed to gradually decrease over time (the logarithmic model) compared to when this rate of change was constrained to be constant over time (the linear model). The results of the longitudinal analyses predicting change in SRH are displayed in Table 2. In all the models, time is defined as the number of weeks after the four-month follow-up. Model 1 indicated that SRH at baseline was highly predictive of SRH at follow-up. There was an overall decrease in SRH over time after the four-month follow-up for both groups of participants. In addition, there was a significant negative interaction between SRH at baseline and time, indicating that those whose health was worse at baseline had lower rates of decline in health over time, largely due to floor effects. The significant main effect for sex indicates that at the four-month follow-up, female caregivers reported poorer SRH on average than males. There was a significant caregiver age-by-time interaction. The negative valence of the estimate indicated that,
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Mittelman et al.
TABLE 2. Logarithmic Model of Change in Subjective Reported Health from Baseline to Year 3 Variables in Model Model 0 SRH at baseline (centered) Caregiver age (centered) Caregiver sex (female ⫽ 1, male ⫽ 0) Time (weeks after 4-month assessment, logarithmic) SRH at baseline ⫻ time Caregiver age ⫻ time Model 1 SRH at baseline (centered) Caregiver age (centered) Caregiver sex (female ⫽ 1, male ⫽ 0) Time (weeks after 4-month assessment, logarithmic) Group (treatment ⫽ 1, usual care ⫽ 0) SRH at baseline ⫻ time Caregiver age ⫻ time Group ⫻ time Model 2: Effect of patient placed in nursing home and patient deceased in addition to Model 1 Patient in nursing home (nursing home ⫽ 1, remaining home ⫽ 0) Patient deceased (deceased ⫽ 1, alive ⫽ 0) Group Group ⫻ time Model 3: Symptoms of depression in caregiver in addition to Model 1 Depressive symptoms Group Group ⫻ time Model 4: Satisfaction with social support in addition to Model 1 Social support Group Group ⫻ time Model 5: Depressive symptoms and satisfaction with social support in addition to Model 1 Depressive symptoms Satisfaction with social support Group Group ⫻ time
b
SE
t
p
0.772 ⫺0.005 ⫺0.246 ⫺0.265 ⫺0.113 ⫺0.017
0.040 0.007 0.104 0.039 0.027 0.004
19.19 ⫺0.73 ⫺2.37 ⫺6.74 ⫺4.17 ⫺3.74
⬍0.001 0.463 0.018 ⬍0.001 ⬍0.001 ⬍0.001
0.772 ⫺0.005 ⫺0.213 ⫺0.240 0.343 ⫺0.112 ⫺0.016 ⫺0.054
0.040 0.007 0.103 0.056 0.117 0.027 0.004 0.079
19.33 ⫺0.77 ⫺2.06 ⫺4.27 2.93 ⫺4.15 ⫺3.71 ⫺0.68
⬍0.001 0.443 0.039 ⬍0.001 0.003 ⬍0.001 ⬍0.001 0.498
⫺0.101 0.196 0.330 ⫺0.046
0.085 0.129 0.117 0.079
⫺1.18 1.52 2.83 ⫺0.59
0.236 0.128 0.005 0.556
⫺0.066 0.242 ⫺0.061
0.005 0.113 0.076
⫺13.08 2.14 ⫺0.81
⬍0.001 0.032 0.417
0.139 0.255 ⫺0.057
0.025 0.118 0.078
5.49 2.17 ⫺0.72
⬍0.001 0.030 0.470
⫺0.064 0.040 0.221 ⫺0.062
0.005 0.026 0.114 0.076
⫺11.82 1.55 1.94 ⫺0.82
⬍0.001 0.122 0.053 0.413
Notes: Model 0: time df ⫽ 377, all other effects df ⫽ 1,592; Model 1: time df ⫽ 376, all other effects df ⫽ 1,593; Model 2: time df ⫽ 376, all other effects df ⫽ 1,591; Model 3: time df ⫽ 376, all other effects df ⫽ 1,592; Model 4: time df ⫽ 376, all other effects df ⫽ 1,592; Model 5: time df ⫽ 376, all other effects df ⫽ 1,591.
after controlling for the other predictors, older caregivers’ health deteriorated more quickly than younger caregivers’ health. Over and above the effects of these covariates, four months after baseline the caregivers in the treatment group had significantly better SRH than those in the control group. The betas, which are regression coefficients, represent the difference in SRH corresponding to a difference of one unit in the independent or predictor variable. Thus, for example, at the four-month assessment, caregivers in the treatment group (1) were 0.34 units higher on the measure of SRH than caregivers in the usual care group (0), 7.21 versus 6.87, respectively (Table 2). In terms of effect size, this represents a difference of 0.23 SD units (0.34/1.50). The group-by-time interaction effect was not significant.
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Comparisons of the covariate-adjusted least squares means for the two groups indicated that the significant group difference was maintained over the first two years of follow-up (Fig. 1). The group effect gradually decreased from 0.34 units at four months to 0.25 units at two years (t(1593)⫽1.96, p⫽0.05) to 0.23 units at three years (t(1593)⫽1.52, p⫽0.13). Analysis of the residual variance across participants indicated that 3.0% of the variance in SRH that was unexplained by the covariates in the reference model could now be explained by the treatment group effect. In model 2, patient status variables were added to the variables included in model 1. Neither placing the patient in a nursing home nor patient death were significantly associated with caregiver SRH. The addition of patient status did not improve model fit
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FIGURE 1.
Predicted Self-rated Health Scores from a Logarithmic Model Over the First Three Years of the Intervention, Controlling for Caregiver Sex and Age, Patient Age, and Group-by-time Interactions
(AIC⫽ 7156.4 for model 1 versus 7157.2 for model 2) and did not notably alter the effect of the intervention. In models 3 and 4, we examined the effects on SRH of depressive symptoms and satisfaction with social support respectively. Depressive symptoms had a significant effect on SRH, with more depressive symptoms being associated with worse SRH. The intervention still had a significant effect, albeit smaller, indicating that not all of the intervention’s effect on SRH was due to improvements in caregiver depressive symptoms. Forty-three percent of the residual variance explained by treatment group in model 1 was found to be overlapping with and potentially mediated by changes in depressive symptoms, whereas 57% was not. Model 4 results indicate that satisfaction with social support also explained a significant amount of the variability in SRH, but that the group effect was still significant. Of the residual variance explained by treatment group in model 1, 50% was mediated by social support, whereas 50% was not. In the final model, we entered both depressive symptoms and social support, and the group effect on SRH was no longer significant, nor was the effect of satisfaction with social support, although depressive symptoms were still a significant predictor of SRH. Of the residual variance explained by treatment group in model 1, 53% was mediated by the combination of depressive symptoms and social support and 47% was not.
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It should be noted that, in a subsidiary analysis (not shown), we determined that support group participation was not a significant predictor of change in SRH over time. Change Over Time in Number of Physical Illnesses Reported In a secondary analysis, using the same methods and predictors as were used in model 1 for the analyses of SRH, we examined potential differences between the treatment and control groups in the number of illnesses reported in the three years after enrollment. Paralleling the results of the analyses for SRH, we found a significant difference between the groups beginning at four months (b⫽⫺0.188, t(1594)⫽⫺2.05, p⫽0.040), but no group-by-time interaction. Comparisons of the covariate-adjusted least squares means indicated that the significant group difference was maintained over the first six months of follow-up (b⫽⫺0.158, t(1594)⫽⫺1.96, p⫽0.0498 at six months). There was a significant main effect for time, indicating that both groups reported more illnesses as time went on (b⫽0.098, t(376)⫽2.35, p⫽0.020).
DISCUSSION Our findings suggest that the enhanced support intervention led to significant benefits to caregiver self-
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Mittelman et al. rated health. While both groups showed worsening SRH over time, the treatment group showed less of a decline in the first four months after enrolling in the study, which was when the formal counseling sessions took place. This suggests that there was a delay in the negative health effects of caregiving as a result of intervention. The six individual and family counseling sessions took place in the first four months. In several previous publications, we have shown that the intervention group showed improved caregiver social support compared with controls during the first four months of intervention41 but that differences in caregiver appraisal and depressive symptoms are not significant until the eight-month follow-up.28,29 Thus, we believe that the immediate improvements caregivers experienced in social support after beginning the intervention may have also led to improvements in their perceptions of health, probably because they had more emotional and tangible support from family members. The NYU intervention included family counseling sessions aimed at rallying available family supports to provide more concrete assistance with caregiving and emotional support. Commonly available interventions, such as support groups, do not include components that directly recruit family members to enhance support, which was a key component of our intervention. The relative stability in SRH after caregivers participated in individual and family counseling sessions appears to be a significant secondary benefit of the intervention. While part of the effect of the intervention on SRH was related to improvements in other caregiver outcomes, there was also a direct effect on SRH that could not be explained by any single other beneficial outcome of the intervention. We observed a similar benefit to the number of illnesses reported by caregivers. The intervention appears to be associated with a delay in the decline in physical health that is commonly found with aging and accelerated by caregiving. The finding that a psychosocial intervention, emphasizing enhancement of social support, led to improvements in caregiver health may seem surprising because the intervention did not have an explicit emphasis on exercise, health promotion, vaccination, or other specific health-related behaviors. However, the mediation analyses suggest that improving satisfaction with social support had a health-enhancing effect on family caregivers. Social connectedness has
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long been considered a central aspect of health.42 Although the mechanisms for such effects are not well understood, tangible and emotional assistance from family and friends helps avoid the negative impact of loneliness and social isolation on health.43 A recent longitudinal study of 1,576 elderly individuals found that mean SRH did not decline, even in individuals over age 70 years, until the six-year follow-up.44 In the present study, we found that caregivers in both the treatment and control groups experienced declines in SRH over a three-year period. Previous research has found that caregivers enter the role with better than average health, but once in the role show more rapid deteriorations in health over time than noncaregivers. In our study, while less than 25% of caregivers judged their health as fair or poor at baseline (23.14% in the treatment group, compared to 19.70% in the control group), by the time of the one-year follow-up, poor or fair health was reported by 30.27% in the treatment group and 36.31% of the control group. Thus the proportion of subjects with fair to poor health increased by about 7% in the treatment group, while for controls the increase was about 16.6%—more than twice as large. In addition, it is noteworthy that the oldest caregivers experienced the highest rates of decline in health, which suggests that caregiving adds to the risk of decline in SRH that occurs with advanced age. Recent research suggests that SRH is not just a byproduct of depressive symptoms. In fact, the reverse may be true.22 SRH is a powerful prospective predictor of a number of important health outcomes, including depression and mortality. SRH is a measure that can capture the complex interactions among illnesses and the wide variability of severities, allowing each individual to make a differential weighting of each illness, taking into account the presence or absence of health problems, functioning, positive and negative health behaviors, and health services utilization.45,46 SRH is a particularly meaningful concept in assessing the physical health status of the elderly, many of whom suffer chronic illnesses, as it provides a summary of a large number of variables related to overall physical well-being.47 Our findings are consistent with other research48 showing that interventions that improve depressive symptoms in older adults can also improve health. Our findings are unique, however, in demonstrating that
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Preserving Health of Alzheimer Caregivers these health benefits are apparent even after controlling for the effects of intervention on depression, and in showing that improvements in health are mediated by improvements in social support. While the effects on SRH found in our study are relatively small (3% of longitudinal variance in SRH was explained by the intervention effect), as has also been noted in similar research,48 if it were multiplied by the number of spouse caregivers in the United States today it would be considered a major public health success. Participants in the control group received considerable benefit from the availability of counseling on an as-needed basis. This undoubtedly decreased the apparent differential effect of the intervention. Moreover, the participants in this study were relatively healthy and the intervention might have an even larger effect on more vulnerable older caregivers. Our findings add to a growing literature documenting the benefits of caregiver interventions.49 It has become increasingly apparent that, in order to be maximally effective, these interventions should include a structured component and be provided over a long period of time. These results are consistent with the more general conclusion that physical and mental health are richly intertwined, and that interventions that enhance psychological well-being may improve health through multiple mechanisms including improved self-perceptions, and alterations in the cardiovascular and immune systems.50 The effects of the NYU intervention on SRH suggest promising new directions for research. Selfrated health has limitations in that it is a nonspecific measure and potentially subject to the biases of all
self-reported measures, despite its value at predicting illness and mortality. Our measure of number of illnesses also was not weighted by severity of illness. Future research into the impact of psychosocial interventions for caregivers on specific biological outcomes such as immune function or mortality can help delineate the pathways through which these interventions may affect physical health. Additional studies that, like the NYU study, include a large number of caregivers and have long-term follow-ups are essential to elucidate the mechanisms through which psychosocial interventions improve caregiver well-being. Further research that moves health-enhancing psychosocial intervention into the broader community of caregivers and demonstrates the utility of intervention outside of academic settings51 and with more culturally diverse caregivers is a vital step that deserves attention. Most caregivers still do not have access to psychosocial interventions other than support groups. Counseling and support hold promise as a means of preserving health among vulnerable dementia caregivers who are at risk not only for declining health, but also increased mortality.34 This work was supported by grants from the National Institute of Mental Health (R01 MH 42216), the National Institute on Aging (R01 AG14634), the Alzheimer’s Disease Core Center (P30-AG08051), and the Florida Alzheimer’s Disease Research Center (P50-AG025711 to WEH). The authors thank the NYU Caregiver Counseling staff, Steven Ferris, Ph.D., and the caregivers for their participation.
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