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.
To examine the association between sibling death in childhood and subsequent mortality risk.
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.
Participants were classified as exposed if a sibling died in childhood (age