Pregnancy accounts for most of the gender difference in prevalence of familial RLS

Abstract Objective This study was designed to evaluate the associated risk of RLS with pregnancy in relation to the family history and the age of symptom onset of RLS. Methods and subjects Data from a prior RLS family history study in which 1019 subjects (527 males, 492 females) were interviewed, provided a diagnosis and characterization of RLS and determination of pregnancy status on which the current study analysis was undertaken. Results In the family members of RLS probands, the prevalence of RLS was significantly higher for parous women than for nulliparous women (49.5% vs. 33.7%, OR = 1.92, 95% CI = 1.16–3.19) or for men (49.5% vs. 30.0%, OR 2.29, 1.69–3.10), but no different for nulliparous women compared to men (33.7% vs. 30.0%, OR 1.19, 0.72–1.96). When only those whose RLS started at or after age 30 were considered, similar differences occurred. These differences were not observed among family members of control probands. Conclusions These data indicate pregnancy has a major impact on the risk of developing RLS for those with a family history of RLS. This pregnancy effect appears to account for most of the gender differences often reported in overall RLS prevalence data.