Familial risk of early- and late-onset multiple sclerosis: a Swedish nationwide study

BackgroundPersons who develop multiple sclerosis (MS) at a young age may bear a higher genetic risk load than persons who develop MS later in life; however, the contribution of familial influence to the risk of MS, in relation to onset age, has not been established.ObjectiveTo investigate the familial risk of MS at two extremes of the spectrum of MS onset age: early onset (first MS symptom <18years of age) and late onset (first MS symptom 50years).MethodsNationwide registries in Sweden were used to identify cases of MS and controls, and their familial relations. We estimated the odds ratio (OR) of an MS diagnosis for individuals with a relative diagnosed with early-onset or late-onset MS compared with those whose relatives did not have MS, using a nested case-control design.Results629 early-onset and 1148 late-onset MS patients were identified and matched to 10 controls from the general population by age and sex. The OR of MS for individuals with a first-degree relative diagnosed with early-onset MS was 10.86 (95% CI 6.87-17.17); and for late-onset MS was 8.08 (95% CI 6.12-10.67).ConclusionsOur findings demonstrate no substantial differences in familial risk in persons with early- and late-onset MS.