Association of Mortality With the Death of a Sibling in Childhood.

Importance: The death of a close relative is associated with an increased mortality risk among the bereaved, but much less is known about the potential association of the death of a sibling in childhood with mortality in this population. Objective: To examine the association between sibling death in childhood and subsequent mortality risk. Design, Setting, and Participants: This population-based cohort study of 5 005 029 participants evaluated linked national registers in Denmark (January 1, 1973, through December 31, 2009) and Sweden (January 1, 1973, through December 31, 2008). A total of 2 060 354 Danish and 2 944 675 Swedish children who survived the first 6 months of their life were included. We excluded 14 children who died of the same external cause as their siblings within 30 days. Data were analyzed from November 2, 2015, through October 14, 2016. Exposures: Participants were classified as exposed if a sibling died in childhood (age <18 years). Main Outcomes and Measures: Poisson regression was used to estimate mortality rate ratio (MRR) with the exposure as a time-varying variable. Results: Among the 55 818 participants who experienced sibling death in childhood (51.5% male and 48.5% female; median age at loss, 7.0 [interquartile range, 3.3-12.1] years), all-cause mortality risk was increased by 71% (MRR, 1.71; 95% CI, 1.57-1.87) during the follow-up of 37 years. The excess mortality risk was observed for groups with specific causes of death, and the higher MRRs were found when the sibling pairs died of the same cause (death due to disease [MRR, 2.16; 95% CI, 1.87-2.49]; death due to external cause [MRR, 1.91; 95% CI, 1.54-2.37]). The increased mortality risk after sibling death was seen across the follow-up period, regardless of the age at bereavement and the type of death among bereaved siblings, but the magnitude of association was stronger during the first year after sibling death (MRR, 2.51; 95% CI, 1.79-3.54). Higher MRRs were found among sibling pairs with the same sex (MRR, 1.92; 95% CI, 1.70-2.18) and close age (MRR, 1.94; 95% CI, 1.58-2.37). Conclusions and Relevance: Bereavement in childhood because of the death of a sibling was associated with an increased risk for mortality in the short and long term. Health care professionals should be aware of individuals' vulnerability due to sibling death, especially for sibling pairs of close age or the same sex. Social and health care support may help to minimize the potential adverse effects on the bereaved sibling.