The times we are born into and our lifestyle choices determine our health trajectories in older age - Results from the KORA-Age study.

Health projections often extrapolate from observations in current ageing cohorts, but health in older age may depend not only on individual characteristics but also on a person's historical context. Our objective was to investigate how health deficit accumulation trajectories after age 65 differed in five adjacent birth cohorts and according to individual life course characteristics. Data originate from the 2008/09 KORA (Cooperative Health Research in the Region of Augsburg)-Age cohort study from Southern Germany and their 2012 and 2016 follow-ups. Deficit accumulation was assessed using a Frailty Index. The effects of birth cohort membership and individual life course characteristics on deficit accumulation trajectories were analyzed using generalized linear mixed models. Out of 2701 participants (49% male) from five birth cohorts (1919-23, 1924-28, 1929-33, 1934-38, 1939-43), we included 2512 individuals with 5560 observations. Frailty Index levels were higher for women, smokers, alcohol abstainers, obese participants and persons with a sedentary lifestyle or living below the poverty threshold. We found higher age-specific Frailty Index levels for the two most recent birth cohorts (e.g. 61%, CI: [13%; 130%] for the 1934-38 as compared to the 1919-23 cohort), but the rate of deficit accumulation with age (7% per life year, (CI: [5%, 9%]) was cohort-independent. Results indicate that the historical context (birth cohort membership) may influence the number of accumulated health deficits after age 65 in addition to poverty and other individual life course characteristics, but BMI, physical activity and smoking remain the modifiable risk factors offering the highest prevention potential.