The changing contribution of childhood social characteristics to mortality: a comparison of Finnish cohorts born in 1936-50 and 1961-75.

backgroundLife course epidemiology suggests that early life circumstances affect adult mortality, but most of the evidence is based on cohorts born in the beginning of the 20th century. It remains unclear whether and how the influences of early life circumstances on mortality have changed in later birth cohorts.

methodsAnalyses rely on 10% register-based samples of households drawn from the 1950 and the 1975 Finnish censuses, with consistent follow-up of socioeconomic and housing-related characteristics and early mid-life mortality (at ages 30-55 years). We estimate survival models for the associations between childhood circumstances and all-cause, internal and external mortality for cohorts born in 1936-50 and 1961-75 adjusting for attained social characteristics. We estimate sibling intraclass correlations as summary measures of all early life and familial influences.

resultsAdverse childhood social circumstances were typically associated with about 10-30% excess cause-specific mortality. These associations were almost fully attenuated by adjustment for achieved later life social characteristics. Early life influences have grown over time for mortality from external causes, particularly as related to home ownership and family type. Differentials have remained stable for internal causes. The intraclass correlations further confirmed the increasing association of early life circumstances on external-cause mortality.

conclusionsOur analyses show that the associations between childhood characteristics and mid-life mortality are substantial and almost fully mediated by achieved adult social characteristics. The increase in the contribution of childhood circumstances to mid-life mortality is driven by ever stronger associations with external causes of death.