Enjoying life and living healthier : impact of behavioral and psychosocial factors on physical function in old age

Declines in physical function vary substantially across older individuals due to, among others, several extrinsic modifiable factors. In this thesis, we aimed to better delineate the impact and interplay among indicators of behavioral, psychological and social well-being on functional trajectories, in initially healthy older individuals. All studies were based on data from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), a population-based study including 3363 older individuals (at baseline) aged ≥60 years living at home or in institutions in Stockholm, Sweden. Data from baseline and first four follow-ups of SNAC-K (years 2001-2015) were used. Study I. We investigated the association between baseline levels of psychological and social well-being and 12-year changes in physical function among 1153 physically and cognitively healthy older adults. Higher levels of psychological and social well-being were significantly associated with a slower decline in physical function. The strongest effect was observed for individuals with highest baseline levels of both psychological and social well-being. Study II. We explored whether higher adherence to Mediterranean Diet (MD), and its interplay with levels of physical activity and social support, were associated with mobility and muscle strength changes among 1686 functionally healthy older individuals. Higher adherence to MD was associated with a slower deterioration of mobility and muscle strength. The potentially beneficial effect of MD was greatest among individuals with highest baseline levels of social support and physical activity, beyond the combined effect of exposures. Study III. In a sample of 1488 healthy older individuals, we examined how behavioral, social and psychological well-being indicators clustered together into well-being profiles. We further explored the association of such profiles with mobility-limitation-free survival over a 15-year follow-up. The three profiles that were identified followed a clear worst-intermediate-best gradient across all indicators. Men in the intermediate and best profiles survived 1 and 3 years longer without mobility limitation, respectively, than those in the worst profile; these figures were 2 and 3 years for women. Study IV. We traced aging trajectories of functional, behavioral, psychological, and social well-being, and explored their association with 16-year mortality. Well-being domains declined at different rates, with the steepest declines seen for functional well-being, followed by behavioral, psychological and social well-being. For all well-being domains, the risk of death was lower among persons with higher baseline values and slower longitudinal declines in that specific domain. Conclusions. Higher levels of behavioral, psychological and social well-being may contribute to delaying the age-related decline in physical function, both independently but even more so when high levels across different domains coexist. This highlights the existence of synergistic effects across domains and confirms the multidimensionality of successful aging. Moreover, the slower decline of behavioral, psychological and social vs functional well-being domains may suggest that the former could act as potential compensatory mechanisms of physical health deterioration. Altogether, these findings strengthen the scientific evidence for healthcare professionals and public health specialists to promote health across different dimensions of older people’s lives, preferably through multi-domain interventions