To Örebro University

Death anniversaries may trigger stress responses that negatively affect health in bereaved individuals. Little is known about such reactions after adult sibling loss. This study examined whether mortality risk increases around the anniversary of a sibling's death. Using Swedish national register data (1990-2016), we conducted a time-stratified case-crossover study including 12,789 adults who experienced sibling loss and later died. Conditional logistic regression estimated associations between mortality and death anniversaries (including pre- and post-anniversary periods), adjusting for time-invariant confounders. Analyses were stratified by the bereaved's sex and age, the sibling's sex, sibling order, and whether ≥1 parent was alive at the bereaved's death. Among women, mortality risk was lower on the anniversary date (OR 0.44; 95% CI 0.21-0.93), and in the period from one day before and up to the anniversary date for women who lost a younger or same-age sibling (OR 0.45; 95% CI 0.20-1.00). In contrast, men bereaved before age 50 had a heightened risk in the period ranging from 12 days before and up to the anniversary (OR 1.40; 95 % CI 1.05-1.86). Overall, sibling-death anniversaries were not associated with elevated mortality, though observed sex- and age-specific patterns merits further investigation.