Experiences of childhood adversity are common and have profound health impacts over the life course. Yet, studying health outcomes associated with childhood adversity is challenging due to a lack of conceptual clarity of childhood adversity, scarce prospective data, and selection bias. Using a 65-year follow-up of a Swedish cohort born in 1953 (n = 14,004), this study examined the relationship between childhood adversity (ages 0-18) and premature all-cause mortality (ages 19-65). Childhood adversity was operationalized as involvement with child welfare services, household dysfunction, and disadvantageous family socioeconomic conditions. Survival models were used to estimate how much of the association between child welfare service involvement and mortality could be explained by household dysfunction and socioeconomic conditions. Results show that individuals who were involved with child welfare services had higher hazards of dying prematurely than their majority population peers. These risks followed a gradient, ranging from a hazard ratio of 3.08 (95% CI: 2.68-3.53) among those placed in out-of-home care, followed by individuals subjected to in-home services who demonstrated a hazard ratio of 2.53 (95% CI: 1.93-3.32), to a hazard ratio of 1.81 among those investigated and not substantiated (95% CI: 1.55-2.12). Associations between involvement with child welfare services and premature all-cause mortality were robust to adjustment for household dysfunction and disadvantageous family socioeconomic conditions. Neither household dysfunction nor socioeconomic conditions were related with mortality independent of child welfare services involvement. This study suggests that involvement with child welfare services is a viable proxy for exposure to childhood adversity and avoids pitfalls of self-reported or retrospective measures.

Child welfare involvement reflects childhood adversity and is associated with increased adult mortality, but it remains unclear how this association changes over the life course. Drawing on the Stockholm Birth Cohort Multigenerational Study (Sweden) and the National Childhood Development Study (Great Britain) this study examines whether inequalities within these cohorts diverge or converge. Involvement with child welfare services (ICWS) is divided into two levels ('child welfare contact' and 'out-of-home care'). For each cohort, we quantify absolute health inequalities as differences in cumulative probabilities of death (18-58 years) and temporary life expectancy; and relative inequalities as hazard ratios in ten-year intervals and ratios of lifetime lost. Persistently, ICWS was associated with premature mortality. The strength of the association varied by age, sex and level of ICWS. Consistently across both countries, the most robust relationship was between out-of-home care and mortality, with statistically significant age-specific hazard ratios ranging between 1.8 and 3.4 for males and 1.8-2.1 for females. Child welfare contact that did not result in out-of-home placement showed less consistent results. Among females the mortality gap developed later compared to males. Estimates attenuate after controlling for family socioeconomic and other background variables but patterns remain intact. Our results show that absolute inequalities widen with increasing age, while relative inequalities might peak in early adulthood and then stabilize in midlife. The relative disadvantage among looked-after children in early adulthood is heightened by overall low rates of mortality at this age. Absolute inequality increases with age, highlighting the weight of the accumulation of disadvantage in mortality over time. The bulk of excess deaths that could be attributed to ICWS occurs from midlife onwards. Mechanisms that uphold the disadvantage after childhood experiences require further exploration. This study highlights that the association between out-of-home care and premature mortality seems to transcend welfare systems.