Prevalence of restless legs syndrome with pregnancy and the relationship with sleep disorders in the Japanese large population

This study re-examined the prevalence of restless legs syndrome (RLS) among pregnant women in Japan based on the diagnostic criteria of the International Restless Legs Syndrome Study Group (IRLSSG), and to epidemiologically clarify factors associated with RLS, including sleep disorders and pregnancy status. A cross-sectional survey was conducted at 344 clinical obstetric institutions in Japan. A total of 19 441 women with a confirmed pregnancy were instructed to complete a self-administered questionnaire during the time they spent waiting for a consultation. univariate and multiple logistic regression analyses were used. The prevalence of RLS among the women was 2.9%. The prevalence by age group exhibited a U-shaped curve with the value for those in their thirties as the minimum. The prevalence became more than twice higher in the third trimester of pregnancy. There were stronger associations between RLS and the third trimester of pregnancy, multipara, smoking, subjective insufficient sleep, difficulty initiating sleep, early morning awakening and excessive daytime sleepiness (OR: 1.92, 0.76, 1.54, 1.68, 2.44, 1.80, 1.89, respectively). The prevalence of RLS among pregnant women in Japan was not as high as previously reported, similar to that for the general Japanese population. As the prevalence of RLS is lower than that in Western countries, genetic backgrounds may contribute more to the observed differences than pregnancy does. In this study, like others, the prevalence of RLS increased during the third trimester of pregnancy, and strong associations were observed between RLS and difficulty initiating sleep and between RLS and difficulty maintaining sleep.