Disease accumulation across birth cohorts in South Korea

Abstract

When someone is born dictates the environment, society, and historic events that they will experience and share with other members of their birth cohort as they age. The age at which an individual experiences an adverse event, combined with their early and later-life characteristics, are important determinants of their health and mortality at older ages. South Korea has undergone several major shocks and changes in the last century, including Japanese annexation, North/South division, catastrophic war, and rapid industrialization. The short time in which these developments occurred, combined with South Korea’s rapid aging and low fertility, provides a unique setting to investigate differences in health by birth cohort. This study aims to examine how the rate of disease accumulation differs across cohorts born during the Japanese annexation (1932-1944), Korean liberation (1945-1949), Korean War (1950-1953), and Post-war (1954-1961) periods. Data are from eight waves of the Korean Longitudinal Study of Aging (2006-2020) and our sample includes 8,266 participants aged 50-74 years. Using Poisson regression models with standard errors clustered at the individual level, we find that the disease accumulation rate increases with younger cohorts. The two younger cohorts have the highest annual rate of disease accumulation (9%), followed by the two older cohorts (5%). We also compute predicted disease counts and find that while the oldest Japanese annexation (1932-1944) cohort has the most disease at younger ages, from age 63, the younger cohorts, especially the Post-war (1954-1961) cohort, quickly surpass them. These trends demonstrate that despite improvements in living standards, socioeconomic factors, and healthcare over time, younger cohorts are developing more disease at a faster rate than their older counterparts. This indicates a need to better understand the factors that might be driving this development so that measures to mitigate the speed of accumulation can be implemented accordingly.