Impact of combinations of subscale declines in higher-level functional capacity on 8-year all-cause mortality among community-dwelling older Japanese adults

Abstract

Background: The frequency of combined declines in domains of multi-faceted frailty and their impact on adverse health outcomes have not been adequately investigated. We aimed to examine the association between combined subscale declines in higher-level functional capacity and 8-year all-cause mortality among community-dwelling older Japanese individuals and the impact of multi-faceted frailty on mortality.

Materials and methods: We administered a questionnaire to 7015 community-dwelling older adults aged 65-85 years. The higher-level functional capacity of the 3381 respondents was assessed using the Tokyo Metropolitan Institute of Gerontology Index of Competence. Subscale decline was defined as (1) none, (2) only social role (SR), (3) only intellectual activity (IA), (4) SR and IA, (5) only instrumental activities of daily living (IADL), (6) IADL and SR, (7) IADL and IA, and (8) all. Associations between combined subscale declines and mortality were examined using adjusted Cox proportional hazards models. Follow-up was conducted from October 1, 2012, to death or November 1, 2020.

Results: The mortality rate was 16.7/1000 person-years. Moreover, 44% of respondents had declined SR, and half of them had multiple declines. Compared with no decline, SR (adjusted hazard ratio [HR]: 1.49, 95% confidence interval [CI]: 1.14-1.93), SR and IA (HR: 1.59, 95% CI: 1.16-2.17), IADL and SR (HR: 1.97, 95% CI: 1.31-2.99), and all-domain (HR: 2.72, 95% CI: 1.98-3.74) declines were significantly associated with higher mortality risks.

Conclusions: Overlapping SR and IADL declines increased mortality risk, suggesting the importance of measuring social frailty and overlapping physical and social frailty.

Keywords: All-cause mortality; Community-dwelling older adults; Frailty; Higher-level functional capacity.