In a large cohort of community-based older persons free of dementia, we found that greater purpose in life was associated with a substantially reduced risk of incident disability, including impairment in basic and instrumental activities of daily living and mobility disability. Our results were robust in that they were unchanged even after controlling for a wide variety of potential confounding variables, including global cognitive function, depressive symptoms, neuroticism, social networks, income, physical frailty, and vascular risk factors and diseases. Further, the association of purpose in life with disability persisted after varying the cut-off score used to define disability to make it more conservative. These findings suggest that having a sense of purpose in life is associated with maintenance of functional independence in old age.
Although we are not aware of any prior study that examined the association of purpose in life with the subsequent risk of developing disability, emerging data suggest that related psychological factors are associated with the development of disability in old age[31
]. For example, neuroticism and harm avoidance have been associated with an increased risk of disability, and extraversion and conscientiousness have been associated with a reduced risk of disability[31
]. Purpose in life is a psychological construct that has long been hypothesized to buffer against adverse health outcomes and that has been shown in cross-sectional studies to be associated with psychological health, including happiness, satisfaction, and self-acceptance[1
]. This study extends recent findings from the same cohort showing that purpose in life was associated with a reduced risk of mortality and Alzheimer’s disease[9
]. Together, these data suggest that purpose in life is associated with a number of important health outcomes and may suggest that a greater focus on positive psychological factors may provide new information regarding successful aging.
At present, the basis of the association of purpose in life with disability is unknown. One hypothesis is that purpose in life enhances health directly by contributing to the optimal functioning of multiple physiologic systems. Purpose in life is associated with some important disease biomarkers[36
], including salivary cortisol, the proinflammatory cytokine IL-6r, HDL cholesterol, and waist-hip ratios. Given that vascular conditions and subclinical inflammation (i.e.,
CRP and IL-6) are associated with poorer physical function in older persons[40
], purpose in life may be protective against disability via its beneficial effect on vascular health and immune function. In this study, however, controlling for vascular risk factors and diseases did not alter the relation of purpose in life with disability, suggesting that other mechanisms must be operating. Another possibility is that purpose in life influences engagement in health promoting behaviors and thus indirectly affects health. That is, older persons who have greater purpose may eat better, exercise more, and avoid harmful substances and behaviors compared to those with lower purpose, who may even become self-neglecting. Although we are aware of limited data on the extent to which purpose is related to health promoting behaviors, one study reported that a greater sense of purpose in life was associated with better breast health behavior in women[43
]. Purpose in life may confer health benefits directly or indirectly, and future research is needed to determine how it operates.
The finding that purpose in life is associated with a reduced risk of disability has important public health implications. In particular, these findings may suggest an important aspect of the assessment of older adults and provide a new target for interventions aimed to reduce the burden of disability. In focus groups, older adults themselves describe purpose in life as a key component of successful aging [44
]; this in conjunction with these and recent findings suggests that purpose may be an important psychological factor to consider when trying to identify older persons at risk for adverse health outcomes. Further, it may be possible to increase purpose in life via behavioral strategies that teach older persons to actively set goals and identify and engage in personally meaningful activities (e.g.,
via philanthropic, educational, or family-based activities). Importantly, purpose in life may be modifiable even among persons for whom participation in more effortful activities (i.e
., physical activity) is restricted because of underlying health problems. Although we are not aware of interventions focused on improving purpose in life among older adults in particular, an emerging therapeutic intervention referred to as Well-Being therapy includes a focus on purpose in life and may offer some insights[45
]. Further, volunteer programs like the Experience Core may help increase purpose in life among older persons[46
]. If purpose can in fact be increased, then the implications could be far reaching.
This study has some notable strengths, including the assessment of purpose in life in a large group of community-dwelling older persons free of dementia at baseline and who underwent detailed annual structured clinical evaluations to document incident disability. Disability was assessed at evenly spaced intervals with three standardly used scales for up to eight years. Finally, we assessed purpose in life with a standard scale previously shown to have predictive validity for adverse health outcomes in older persons. The main limitations are the selected nature of the cohort, which may have restricted our range of scores on purpose in life and limit the generalizability of findings, and the use of self-report measures of disability. Future studies are needed to elucidate the biologic basis of the association of purpose in life with disability and to examine the association of purpose in life with additional health outcomes in older persons.