The Korean Headache-Sleep Study was a nationwide, cross-sectional survey of headache and sleep in the Korean population in adults aged 19–69 years. The study design and methods were previously described in detail [29, 30]. Briefly, we adopted a 2-stage systematic random sampling method in all Korean territories except Jeju-do proportional to population distribution and sampled 2,695 individuals. Subjects were stratified according to age, gender, and occupation. To minimized interest bias, we informed candidates that the survey topic was “social health issue” rather than headache. Trained interviewers conducted structured interviews, using a questionnaire to diagnose headache and sleep disorders including RLS by door-to-door visit and face-to-face interview. The interview included questions on the symptoms of headache and RLS. All interviewers were employed by Gallup Korea and had previous social survey interviewing experience. The interviewers were not medical personnel. The study was undertaken from November 2011 to January 2012, and was approved by the institutional review board/ethics committee of Hallym University Sacred Heart Hospital and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Written informed consent was obtained from all participants.