Birth cohort divergence in English and European multimorbidity trajectories

Background The rising rates of multimorbidity have important implications for individuals, caregivers, and healthcare systems. Research from North America documents that more recent birth cohorts of older adults are experiencing higher levels of mortality and multimorbidity than earlier cohorts. Methods The present study utilizes data from the English Longitudinal Study on Ageing and the Survey of Health, Ageing, and Retirement in Europe and longitudinal mixed-effects models to examine inter-cohort trends in multimorbidity in England and Europe between ages 40 and 85 years. We also examine whether population shifts in socio-demographic characteristics, health behaviours, or specific chronic conditions explain the cohort divergence. Results There are significant birth cohort differences in age-related trajectories of chronic disease accumulation between ages 40 and 85 years in both populations. More recent cohorts born after World War II experienced significantly more chronic disease than did those born in early cohorts at equivalent ages. In England and Europe, members of the 1946-1950 cohort had accumulated an average of one condition at ages of ∼65 and ∼70 years, respectively, while those born in 1915-1923 did so at ages of ∼80 and ∼85, respectively. Socio-demographic and behavioural factors are related to individual trajectories of chronic disease accumulation, but do not attenuate cohort divergence. The greatest divergence was observed for arthritis, diabetes, and cardiovascular disease. Within Europe, cohort divergence further varies by region. Conclusion Results echo North American patterns of a more rapid accumulation of multimorbidity among recent cohorts. Patterns persist after adjustment for socio-demographic and behavioural profiles, suggesting that the drivers of birth cohort divergence lie with broader structural forces (e.g. shifting epidemiologic environment and diagnostic processes) rather than individual-level characteristics.