The association between intrinsic capacity and functional ability in older adults - exploring the role of the physical environment

BACKGROUND: Ageing in place has been promoted in the Netherlands to encourage optimal functional ability (FA) and independent living among older adults. FA is likely dependent on intrinsic capacity (IC), a composite measure of an individual's mental and physical capacities-and its interaction with the physical environment in which people live. This study aimed to examine the association between IC and FA, as well as to explore how the physical environment may modify this relationship in older adults. METHODS: Data of older adults of the Longitudinal Aging Study Amsterdam were used (n=1,637). FA was assessed as six-year functional decline (yes/no). IC scores (0-100) and characteristics of the physical environment, i.e., urbanisation, air pollution (particulate matter (PM₁₀) and nitrogen dioxide (NO₂)), area-level socio-economic status, and neighbourhood walkability, were assessed at baseline. Multiple logistic regression analyses were conducted to investigate the association between IC and functional decline, and the modifying effect of each environmental variable. RESULTS: The mean age at baseline was 69.39 years (SD=7.51) and 54.7% were women. Higher IC was associated with lower odds of functional decline (OR: 0.90, 95% CI: 0.88-0.93). Stratified analyses showed a stronger inverse association between IC and functional decline in lower PM₁₀ (OR: 0.84, 95% CI: 0.76-0.92), compared to higher PM₁₀ environments (OR: 0.92, 95% CI: 0.89-0.95) in fully adjusted models. CONCLUSION: Higher IC was related to less functional decline. Exposure to higher levels of PM₁₀ appears to mitigate the protective association between IC and FA in older adults.