Longitudinal Norms of Frailty Measured by the Frailty Index: A Cross-National Comparison Using Data from the Survey of Health, Aging, and Retirement in Europe (SHARE)

Abstract

Background: Frailty, a geriatric syndrome commonly used to identify vulnerable older adults, is a public health priority. However, the lack of cross-national comparisons of frailty trajectories and their distribution constrains current understanding of normative changes in frailty for residents across different countries. Objective: To derive longitudinal percentiles of frailty using a consistent cross-country approach. Design: Observational study using longitudinal data from the Survey of Health, Ageing and Retirement in Europe (SHARE) between 2004 and 2020. Setting: We fit the distribution of the FI by Generalized Additive Models for Location, Scale, and Shape (GAMLSS), assessed the role of sex (male/female), education (in years), and migration status (migrant/non-migrant), and estimated the longitudinal percentiles of frailty using a consistent cross-country approach for 16 countries. Participants: Individuals aged >= 65 years (N = 42,951) at study entry. Measurements: Frailty index (FI) based on the accumulation of deficits in 40 items. Results: The results show that education is protective against frailty in all countries (a decrease of 1.1 pp. in Switzerland to 5.7 pp. in Slovenia, all p < 0.001). In most countries, women are frailer than men and migrant individuals have higher levels of frailty than non-migrants. FI trajectories showed heterogeneity across countries. The quantiles for women and migrants suggest frailer trajectories than men and non-migrants respectively. Conclusions: Findings from this cross-national comparison provide a framework within which the longitudinal norms of frailty trajectories from different countries can be interpreted.