Medication overuse headache: a critical review of end points in recent follow-up studies

No guidelines for performing and presenting the results of studies on patients with medication overuse headache (MOH) exist. The aim of this study was to review long-term outcome measures in follow-up studies published in 2006 or later. We included MOH studies with > 6 months duration presenting a minimum of one predefined end point. In total, nine studies were identified. The 1,589 MOH patients (22% men) had an overall mean frequency of 25.3 headache days/month at baseline. Headache days/month at the end of follow-up was reported in six studies (mean 13.8 days/month). The decrease was more pronounced for studies including patients with migraine only (-14.6 days/month) compared to studies with the original diagnoses of migraine and tension-type headache (-9.2 days/month). Six studies reported relapse rate (mean of 26%) and/or responder rate (mean of 28%). Medication days/month and change in headache index at the end of follow-up were reported in only one and two of nine studies, respectively. The present review demonstrated a lack of uniform end points used in recently published follow-up studies. Guidelines for presenting follow-up data on MOH are needed and we propose end points such as headache days/month, medication days/month, relapse rate and responder rate defined as a parts per thousand yen50% reduction of headache frequency and/or headache index from baseline.