RE: “FAMILIAL RISK OF MULTIPLE SCLEROSIS: A NATIONWIDE COHORT STUDY”

Abstract

In a recent register-based Danish cohort study on multiple sclerosis, Nielsen et al. (1) reported a 7.1-fold increased risk of multiple sclerosis in first-degree relatives of multiple sclerosis patients and an 8.6-fold risk in nontwin siblings. Brothers had a high relative risk of 12.6, as compared with sisters' risk of 6.3. The study was based on the Danish Multiple Sclerosis Register for diagnostic data and on the Danish Civil Registration System for family data, available for persons born in the early 1950s. No age-specific data were given, but, at least for siblings, the age span was probably about 0–45 years, because follow-up was terminated at the end of 1997. Based on uniform diagnostic data and registers with high coverage, the results of this study would be expected to be highly reliable. They provide further evidence for the heritable etiology of this disease, for which a family history is thought to be present in up to 20 percent of cases (2–4).