Prospective survey on the natural course of restless legs syndrome over two years in a closed cohort

Objective This study was set out to identify the population with restless legs syndrome (RLS) developing a chronic course and the impact of long-term morbidity of RLS on disorder related dysfunctions. Methods Two population-based epidemiological surveys were performed in 2005 and 2007 on the same cohort in Japan. Questionnaires including demographics, measurement scales for depression, quality of life, subjective sleep disturbances, and the NIH/IRLSSG consensus questionnaire for RLS diagnosis, were distributed to participants, and then telephone interviews were performed to determine the diagnosis and severity of RLS. Results Among 1592 valid respondents, only 20 (40%) of 50 RLS-positive subjects at the first survey were repeatedly RLS-positive at the second survey. The frequency of RLS symptoms at the first survey was associated with the repeated appearance of RLS symptoms (odds ratio 8.70, p =0.0302). The chronic morbidity of RLS seemed to be associated with the existence of depression and subjective sleep disturbance. Conclusions RLS may not be persistent in more than 50% of the affected population. The frequency of RLS symptoms, but not the severity, may predict the persistence of this disorder.