Rate of augmentation and risk factors with long-term follow-up in Japanese patients with restless legs syndrome

Preventing augmentation is the critical clinical issue for RLS treatment. As for augmentation in Asian RLS patients, there have been only four studies and the follow-up durations of these studies were not long. We investigated Japanese RLS patients with longer duration of treatment in a clinical setting. This study is a retrospective assessment of 42 RLS patients with follow-up durations of longer than 18 months (78.4 +/- 29.2, range 19-139) at two urban sleep centers in Osaka, Japan from May 2004 to April 2014. The mean age of first visit was 63.5 +/- 14.1 years old and the estimated age of RLS onset was 47.9 +/- 16.5 years old. Twenty-eight out of 42 patients were female. At initial evaluation, the mean International Restless Legs Scale score (IRLS score) was 22.0 +/- 5.9. Thirty-one of 42 had already visited other clinics before coming to our sleep centers, and the number of clinics visited was 1.3 +/- 0.6. Augmentation developed in two patients (4.8%), and the dosage of dopamine equivalent in patients with and without augmentation was 12.5 and 18.8 mg vs. 15.8 +/- 17.7 mg. In the two RLS patients with augmentation, ferritin was 113.1 and 114.1 ng/mL, respectively, and the number of clinics before coming to our sleep centers was both three. The augmentation rate of Japanese RLS patients from our study is low compared with previous Western and Asian studies. It might be attributable to racial difference, lower dosage of dopaminergic treatment, and the level of ferritin.