Association of Mortality With the Death of a Sibling in Childhood
The authors investigated the association between sibling death in childhood and the mortality risk among bereaved individuals. This is a population based cohort study.
Registry data was used to link live births from 1973-2004 in Denmark and from 1973-2006 in Sweden and identify the mothers and siblings. Children were placed in the exposed group if they were between 6 months to 18 years of age and had a sibling who died at any age. Children were followed until death, emigration or the end of the study. Outcomes were all-cause mortality, cause specific mortality and mortality by type of death (external causes of death or diseases).
55 818 of 5 005 029 participants experienced the death of a sibling in childhood. The median age of the bereaved siblings was 7.0 years at the time of the loss. During the follow-up period, 534 members died in the bereaved group and 25 591 died in the non bereaved group. The bereaved group had an increase in all cause mortality when their sibling died of a disease (MRR 1.72, 95% CI 1.55-1.90) or due to an external cause (1.65, 95% Cl, 1.40-1.94). Bereaved participants also had an excess of death from disease and from external cause as compared to their non-bereaved comparison. Increased mortality risks were found even after adjustment for their co-morbid diseases irrespective of the type of death of their sibling. The strongest association was found within 1 year of the sibling death. The association was also higher in same sex sibling pairs and siblings with a small age difference.
There was no data on the shared social environment of the sibling pairs or of the family environment. There may be interplay between bereavement and other factors such as social and psychological factors that may also affect the association that were not included in the data set analyzed. The study used a national data set in Denmark and Sweden and thus, results may not be generalized to all populations.