Disability trends in selected European countries: an Age-Period-Cohort analysis

Disability is an important public health issue. Understanding the evolution of disability with age is critical for policy makers and researchers to develop effective interventions and allocate resources efficiently. The aim of this study is to describe disability trends in European countries, focusing on age, period and cohort effects. We used data from the Survey of Health, Aging and Retirement in Europe (SHARE). The data were pooled from waves 1 to 9 (excluding wave 3) and we considered only Austria, Belgium, Denmark, France, Germany, Italy, Spain, Sweden and Switzerland, resulting in a sample of 72188 respondents and 234946 rows. The response variables were the global index of activity limitation (GALI), the number of limitations in instrumental (IADL) and non-instrumental activities of daily living (ADL). All three variables were dichotomized. A logistic age-period-cohort interaction model was used to estimate the prevalence for each of the three responses. Cohort effects were estimated as the interaction between age and period. The model was estimated using generalized estimating equation with an unstructured working correlation matrix. Gender and individual country-specific wealth quintile were included as covariates. We found that disability prevalence was lower in men than in women and exhibited a non-linear relationship with age. Additionally, prevalence increased over time, peaking in wave 7 (pre-Covid-19) for GALI only, and decreased with higher wealth quintiles. Country-specific differences were also observed. The cohort effect mitigated the impact of age, except in older cohorts for GALI and IADL.