Risk factors in medication-overuse headache: a 1-year follow-up study (care II protocol).

To investigate factors influencing prognosis in medication-overuse headache (MOH), we conducted a 12-month follow-up of patients with probable MOH. We recruited 215 patients consecutively admitted to our headache centre for an inpatient detoxification treatment. We analysed likely predictor factors for headache resolution (sex, age, primary headache, psychiatric comorbidity, type and timing of overuse). Mann-Whitney U-test and chi-squared test were used. One year after withdrawal, we had complete data on 172 patients (80%): 38 of these patients (22%) had relapsed into overuse and 134 (78%) had not. The negative prognostic factors for relapse were: intake of more than 30 doses/month (P = 0.004), smoking (P = 0.012), alcohol consumption (P = 0.037), non-confirmation of MOH diagnosis 2 months after detoxification (P = 0.000), and return to overused drug(s) (P = 0.000). The 1-year relapse rate was 22%. The existence of sub-groups of MOH patients with such risk factors could influence treatment strategies.