Background: The network approach may provide a framework for understanding intrinsic capacity (IC) as a system underlying functioning. The system's resilience to resist functional decline may arise from the interrelationships among system components, i.e., body functions or capacities. We applied network analysis to investigate whether the interplay between different intrinsic capacities differs according to age and self-rated health (SRH) in older adults.

Methods: The study sample consisted of a population-based cohort of community-dwelling older adults aged 75, 80, and 85 years (men n=356 and women n=469). We quantified five IC domains: vitality, locomotion, cognition, psychology, and sensory, using performance-based measurements and questionnaires, and estimated IC networks for two age (75- vs. 80- and 85-years) and SRH (higher vs. lower) groups separately for sexes. Differences in global network properties (e.g., density, overall connectivity) and centrality indices were compared between the groups.

Results: IC network density (i.e., the number of edges) was higher in the 80- and 85-olds compared to the 75-year-olds, and in the worse compared to the better SRH group in both sexes. However, the differences in edge weights and global strength of the networks were statistically non-significant. Walking speed was the most central node in the estimated networks.

Conclusions: With increasing age and health decline, the IC network seems to become more denser, which may indicate a loss of system resilience. Walking is a more complex activity than the others requiring the functioning of many subsystems, which may explain why it connects multiple domains in the IC network.

Keywords: Complex systems approach; Emergent property; Functional reserves; Healthy aging.

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