This longitudinal study found that respondents reporting fair/poor self-rated health at baseline experienced a greater decline in walking speed in subsequent years compared with those reporting excellent/good self-rated health independent of baseline walking speed and of demographic, physical, and psychological characteristics. Decline in walking speed was greatest among caregivers with fair/poor self-rated health, which differed significantly from the slight increase in walking speed among caregivers with excellent/good self-rated health. Moreover, poorer self-rated health was associated with the largest decline among high-intensity caregivers, whereas it had a more modest relation in other subgroups of caregivers. These results suggest that poorer self-rated health is associated with a decline in walking speed and that greater involvement in caregiving may worsen this decline.
Our overall findings add to the evidence that poorer self-rated health increases the risk of lower-extremity dysfunction (10
). Other studies have established that lower-extremity dysfunction is a risk factor for future disability (8
). Our study results are consistent with the assertion that poorer self-rated health is not only associated with functional decline (4
) but also contributes earlier in the pathway through its association with lower-extremity dysfunction (10
We hypothesized that the act of caregiving would provide the caregiver physical and psychosocial benefits that would protect against the decline in walking speed for those with poorer self-rated health. Caregiving did appear to benefit those with excellent/good self-rated health because their walking speed increased, whereas noncaregivers with similar health ratings experienced a small decrease over time. However, the influence of poorer self-rated health on decline in walking speed was greater among caregivers than among noncaregivers. It may be that these female caregivers with poorer self-rated health continue their caregiving roles despite their own declining health, the high stress of caregiving, and less time to engage in preventive health behaviors (29
) while being less likely to utilize health care services (31
). Caregivers with higher levels of self-rated health may benefit from their caregiving activities and the increased physical activity and leg strength compared with noncaregivers (12
Furthermore, in stratified analyses, caregiving intensity modified the association between self-rated health and change in walking speed. High-intensity caregivers who rated their health as fair/poor experienced the greatest decline in walking speed. These results are consistent with the “wear and tear” theory of caregiving stress. That is, greater involvement in caregiving leads to more stress, resulting in poorer health outcomes. The high-intensity caregivers in our sample may have been more vulnerable to the burden of caregiving (32
). By contrast, we observed an increase in walking speed among low-intensity caregivers with excellent/good self-rated health, suggesting that, when caregiving demands are minimal and caregivers perceive their health as good, these persons have positive functional outcomes. Our results are consistent with those of one study showing that elderly caregivers who were most intensely involved in caregiving had the highest rates of mobility limitation (13
). However, our results differ from previous analyses of Caregiver-SOF that found high-intensity caregivers experienced the least decline in performance-based functioning (21
). These differences may be due to different outcomes and analytic methods: the current study evaluated percentage change in rapid walking speed, whereas our previous analyses evaluated mean change in a composite measure comprising usual walking pace, chair stand speed, and grip strength.
Although these declines in walking speed may appear unsubstantial, even small declines increase the risk of mortality (33
). A clinically meaningful change in walking speed of 0.10 m/second has been established previously (34
), and a decline of this magnitude was observed in our sample among all subjects with fair/poor self-rated health at baseline and among all caregivers and high-intensity caregivers with fair/poor self-rated health at baseline. Additionally, if converted into distance walked over 30 seconds (the time often given to cross a street), then high-intensity caregivers with fair/poor self-rated health would walk 6.93 m less in 30 seconds over 2 years of follow-up compared with baseline, while high-intensity caregivers with excellent/good self-rated health would walk 2.85 m less. This decline in walking speed may affect not only caregivers’ quality of life but also the ability to provide high-quality care to their care recipient.
This study had several potential limitations. We had only a single baseline assessment of self-rated health. Although repeated measures of self-rated health were used in a previous study (10
), we evaluated baseline self-rated health as a potential predictor of functional decline over the next 2 years. In addition, we combined fair and poor self-rated health levels to increase statistical power. Whereas respondents who rated their health as fair or poor experienced declines in walking speed over time, the decline was greater among those with poor ratings. Furthermore, caregiving intensity was based on the median number of ADL and IADL tasks performed and not the number of hours per week spent performing caregiving tasks. ADL and IADL tasks may differ in terms of the amount of time, difficulty, and stress involved; however, number of caregiving tasks performed has been positively correlated with number of hours spent caregiving as well as stress (21
). In addition, our sample of elderly women was largely white and high functioning, so generalizability may be limited.
Our findings support those of a previous study that examined self-rated health and its relation with walking speed as a possible antecedent to ADL limitations in elderly men and women (10
). Our study design enabled us to assess whether performing caregiving tasks modified this relation. A major strength of our study is assessment of walking speed at multiple follow-up points; other studies have relied on a single follow-up measure (6
). Furthermore, our outcome was an objective, performance-based measure rather than a self-reported measure. An additional strength is that the Caregiver-SOF study is part of a large, multisite, community-based study of elderly women; its 2 annual follow-up interviews allowed for time-varying assessment of important covariables. Caregiving was reassessed at each annual interview, which minimized the likelihood of misclassification of caregiver status.
We chose not to adjust for number of chronic conditions and ADL limitations, as in a previous study (10
). Our goal was to evaluate the association between subjective ratings of health and subsequent functional decline, and studies have found that self-rated health is strongly related to these objective measures of health (5
). Indeed, this finding was true because, when we added number of chronic conditions and ADL limitations to our model, the effect of self-rated health disappeared among noncaregivers and decreased substantially among caregivers (data not shown). It seems that self-rated health may act through the pathway of these objective measures of health.
In conclusion, we found that poorer self-rated health was associated with a decline in walking speed, a measure of lower-extremity dysfunction that may precede onset of ADL limitations in the established pathway between self-rated health and mortality. This decline in walking speed was most apparent in high-intensity caregivers. Given the increasing reliance of our health care system on the contributions of informal, elderly caregivers (37
), targeting interventions toward caregivers with poorer self-ratings of health could help maintain their health and ability to continue providing essential care for their recipients.