Healthy aging: how does a multidimensional construct of functional ability predict objective and subjective outcomes?

Background: Despite the comprehensive and holistic conceptual approach proposed by the WHO to measure Functional Ability (FA) in healthy aging, research exploring both intrinsic capacity (IC) and environments is rare. This study aimed to define a multidimensional FA construct based on the WHO framework and investigate its association with objective (mortality, IADL-disability) and subjective (poor life satisfaction, poor perceived health) outcomes.

Methods: The sample included 587 older participants from the AMI (Aging Multidisciplinary Investigation) epidemiological cohort. In total eight subdomains of FA were defined using Structural Equation Models: five related to IC and three to the living environment (from 30 collected variables in total). Cox regression models were used to investigate the association between FA and incident adverse outcomes.

Results: Participants were classified into four levels of FA (34% in very high, 16% in high, 22% in medium, and 28% in low). Compared to those with very high FA, participants with low FA had significantly higher risks of death (Hazard Ratio HR = 2.19; 95% Confidence Interval: 1.30-3.68), IADL-disability (HR = 3.13; 95% CI: 1.99-4.92) and were more likely to experience poor life satisfaction (HR = 1.87; 95% CI: 1.15-3.03) and poor perceived health (HR = 3.97; 95% CI: 1.85-8.53).

Conclusion: Low FA levels are strongly associated with increased risks of both objective and subjective negative outcomes. These findings highlight the importance of simultaneously considering IC and environment to properly explore FA in healthy aging.