Intrinsic capacity impairment and incident dementia across three population-based cohorts: a harmonized individual participant data analysis.

OBJECTIVES: To examine whether intrinsic capacity impairment predicts incident dementia across three countries and to evaluate its value for risk stratification. DESIGN: Harmonized multicohort study with individual participant data meta-analysis. SETTING AND PARTICIPANTS: Community-dwelling adults aged ≥50 years without baseline dementia from CHARLS (n = 17,708), ELSA (n = 9,432), and HRS (n = 22,034). MEASURES: Intrinsic capacity was assessed across five domains: cognition, locomotion, vitality, sensory, and psychological functioning. Multidomain impairment was defined as deficits in ≥3 domains. RESULTS: Pooled hazard ratios rose in graded fashion: 1.31 (95% CI 1.22-1.42) for one impaired domain, 1.65 (1.48-1.85) for two, and 2.41 (2.18-2.68) for ≥3 domains. A Psych-Cognitive impairment pattern approached Multidomain risk (HR 2.15 vs 2.68). Rapid IC decline predicted 42.3% cumulative dementia incidence over six years. Adding IC to a demographic model improved the C-index from 0.69 to 0.76 with net benefit on decision curve analysis. Associations persisted when the cognitive domain was excluded and with death as a competing event; psychological functioning was the most consistent independent domain. CONCLUSIONS: Intrinsic capacity impairment robustly predicts incident dementia across diverse populations. Its low cost and universal applicability support integration into geriatric assessment and primary care for early dementia risk stratification.