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.

To derive longitudinal percentiles of frailty using a consistent cross-country approach.

Observational study using longitudinal data from the Survey of Health, Ageing and Retirement in Europe (SHARE) between 2004 and 2020.

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.

Individuals aged ≥65 years ( N = 42,951) at study entry.

Frailty index (FI) based on the accumulation of deficits in 40 items.

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.

Findings from this cross-national comparison provide a framework within which the longitudinal norms of frailty trajectories from different countries can be interpreted.