A frailty-intrinsic capacity index to predict disability in community-dwelling older Japanese adults

We constructed and validated a frailty-intrinsic capacity (FR-IC) index for predicting disability in community-dwelling older Japanese adults.

This longitudinal cohort study included 1179 participants aged ≥60 years (mean age: 71.3 ± 7.4 years, 51 % men). A multidisciplinary geriatric team constructed a 35-item FR-IC index (score range: 0: robust to 1: severe frailty, accumulation model) comprising 15 domains incorporating the intrinsic capacity concept (IC-Vision, IC-Hearing, IC-Locomotor capacity, IC-Cognition, IC-Vitality, and IC-Psychological capacity) based on questionnaires widely used in Japan. To test predictive validity, age- and sex-adjusted Cox proportional hazard models estimated hazard ratios (HRs) for incident disability (care need levels ≥1) by FR-IC index quartiles using the cohort study's existing data.

The mean FR-IC index score (32 items, three missing) was 0.08±0.05 (range: 0.00-0.31). During a mean follow-up of 9.0 ± 2.8 years, 284 (24 %) adults developed a disability. Compared with the lowest quartile, the adjusted HRs for developing an incident disability in the second to fourth quartiles were 2.32 (95 % confidence interval: 1.15-5.33), 3.18 (1.64-7.15), and 4.15 (2.14-9.32), respectively. The area under the curve of the FR-IC index for incident disability was 0.86. Among healthy participants, defined as robust by the baseline phenotypic physical frailty assessment (n = 437), sex- and age-adjusted HRs for incident support care through the second to third tertiles were 1.72 (0.79-4.30) and 2.51(1.17-6.22), respectively (trend P = 0.028).

The novel FR-IC index can predict future disability among community-dwelling older Japanese adults. Integrating IC into frailty assessments provides a more comprehensive measure of aging.