The risk of multiple sclerosis in bereaved parents - A nationwide cohort study in Denmark

Background: Previous studies have suggested that psychological stress may play a role in the risk of multiple sclerosis ( MS), but the evidence is very limited. Objective: To examine the association between MS and a well-defined major stressful life event: the death of a child. Methods: In this follow-up study based on nationwide and population-based registers, all 21,062 parents who lost a child younger than 18 years from 1980 to 1996 in Denmark were included in the exposed cohort and 293,745 matched parents who did not lose a child in the unexposed cohort. The two cohorts were followed for incident MS from 1980 to 1997. Hazard ratios (HR) with 95% CI were calculated as the measure of association between the exposure and MS, using the Cox proportional hazards regression model. Results: Two hundred fifty-eight MS patients were identified ( 28 in the exposed cohort and 230 in the unexposed cohort). The exposed parents had an increased risk of MS ( HR 1.56, 95% CI 1.05 to 2.31), which is significant only when follow-up was at least 8 years. The HR for definite/ probable MS was 1.42 ( 95% CI 0.90 to 2.24). Parents who lost a child unexpectedly had an HR of 2.13 ( 95% CI 1.13 to 4.03) for all MS, which is higher than that for other bereaved parents ( HR 1.33; 95% CI 0.81 to 2.16). Conclusion: Psychological stress may play a role in the development of MS.