Risk for relatives of patients with multiple sclerosis in central Sardinia, Italy.

Multiple sclerosis (MS) is a chronic, inflammatory, disabling disease of the central nervous system, known for its complex interplay between genetic and environmental factors. We used life table techniques to calculate age-adjusted recurrence risks for different categories of relatives of MS patients from Central Sardinia (Italy), a genetically homogeneous, stable population with a high degree of consanguinity. We included 313 probands and a total of 12,717 relatives in the analysis. The overall age-adjusted recurrence risk for relatives of MS probands is 1.90% [95% confidence interval (CI): 1.57-2.30]. The age-adjusted recurrence risk in parents was 1.26% (95% CI 0.60-2.63), in children 2.33% (95% CI 0.09-5.56), in sibs 4.76% (95% CI 3.57-6.32), in second-degree relatives 0.72% (95% CI 0.42-1.22), and in third-degree relatives 1.79% (95% CI 1.27-2.51). The sex of the probands (male) and of the relatives (female), and the number of affected relatives in the family significantly increase the risk of MS in relatives.