Out-of-home care placement and mortality rate in early adulthood: identifying vulnerable subgroups in a nationwide cohort study

Out-of-home care has been linked to excess mortality across the lifespan. We examined whether this association is modified by the age at first out-of-home care placement and the number of placements. In this population-based cohort study, we used register data covering all children born in Denmark between 1 and 1980 and 31 December 1999, totalling 1,111,193 individuals followed until 31 December 2018. We divided participants according to sex, out-of-home care status, age at first placement, and the number of placements. We estimated adjusted hazard ratios and hazard differences per 10,000 person-years for all-cause mortality and mortality due to suicide, accidents, and cancer between ages 18 and 39. 53,015 (4.8%) of the participants were placed in out-of-home care before age 18. The adjusted hazard ratio for all-cause mortality was 3.4 (95% CI 3.1–3.7) for males and 4.7 (4.0–5.4) for females, corresponding to 20.6 (19.0–22.2) and 10.3 (9.1–11.5) additional deaths per 10,000 individuals annually among males and females, respectively. Associations did not vary substantially according to age at first placement or the number of placements. Both males and females with a history of out-of-home care were more likely to die from suicide, accidents, and cancer compared with their peers. We show a markedly higher all-cause and cause-specific mortality among children who have been placed in out-of-home care, but contrary to our hypothesis, age at first placement and the number of placements did not modify this relation. These results warrant further investigation into potential target points for interventions that may prevent premature mortality in this group of disadvantaged individuals.