Definitions and participant characteristics of frequent recurrent headache types in clinical trials: A systematic review.

Background Clear definitions of study populations in clinical trials may facilitate application of evidence to clinical populations. This review aimed to explore definitions of study populations in clinical trials on migraine, tension-type headache, cluster headache, and cervicogenic headache. Methods We performed a systematic review of clinical trials investigating treatment efficacy for migraine, tension-type headache, cluster headache, and cervicogenic headache.