Association of intrinsic capacity with ADL and IADL trajectories: Evidence from a nationwide longitudinal study.

Background: With global aging, functional decline in older adults is a major public health concern. The WHO introduced Intrinsic Capacity (IC) as a key indicator of healthy aging, yet longitudinal evidence on its association with Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) trajectories remains limited.

Methods: Data were drawn from the China Health and Retirement Longitudinal Study (CHARLS, 2015-2020), including 4368 participants aged ≥60 years. IC was assessed using quartiles, Latent Profile Analysis (LPA) groups, and five IC domains. Group-Based Trajectory Modeling (GBTM) identified ADL and IADL trajectories, while multivariable logistic regression examined associations between IC and ADL/IADL trajectories. Subgroup and sensitivity analyses ensured robustness.

Results: Two trajectory groups were identified for both ADL and IADL: Stable (ADL: 76.5 %, IADL: 76.9 %) and Declining (ADL: 23.5 %, IADL: 23.1 %). LPA revealed three IC profiles: Low Sensory Domain, Low Locomotion and Vitality, and High and Stable IC. Lower IC was significantly associated with higher ADL/IADL decline risk. The Low Locomotion and Vitality Group had increased risk, while the Low Sensory Domain Group showed no significant association. Locomotion, vitality, and psychological function were significantly related to decline, whereas sensory and cognitive domains were not.

Conclusion: Lower IC is significantly associated with ADL and IADL decline, with locomotion and vitality as key predictors. Early screening and interventions to maintain IC may delay functional impairment and promote healthy aging.