Page 54 - The clinical aspects and management of chronic migraine Judith Anne Pijpers

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Chapter 3
(n=85). Therefore, final primary headache diagnosis was used in the analysis. In any case, pre-existing and final headache diagnoses were fairly correlated (n=182, r=0.62, p<0.001). Type of acute medication was classified as: i) triptans, ii) analgesics (paracetamol/acetaminophen and/or NSAIDs), iii) combination of triptans and analgesics, and iv) other medication, comprising opioids, ergots or combinations of those medications with analgesics or triptans. No approval of the local ethics committee was necessary as the study was a retrospective follow-up study and all data were analysed anonymously.
Data analysis and statistics
Baseline characteristics were reported as mean ± SD or absolute numbers with percentages. The number of headache days and medication days at baseline were grouped into daily (30.4 days/month) and non-daily (<30.4 days/month), because of the non-parametric distribution of the data. Differences in means between groups were tested with independent samples t-tests and one-way ANOVAs. Differences in proportions were tested using χ2 tests. Patients were stratified into‘successfully withdrawn’and‘not successfully withdrawn’, the latter including patient who were lost to follow-up. All patients were included in the analysis of the first outcome (successful withdrawal). Successfully withdrawn patients were included in the analysis of the second and third outcomes (response respectively relative reduction). Univariate logistic regression models were used to test crude associations. Analyses were rerun as a multivariate model, adjusting for the potential confounding effects of all variables that were tested in the univariate model. For all analyses, two-tailed p-values < 0.05 were considered as statistically significant. All statistical analyses were performed using SPSS 17.0 (SPSS inc., IBM, USA).
Results
Participants and descriptives
The total study flow is shown in Figure 1. Of 2086 new outpatients, 416 patients were diagnosed with MOH and advised to withdraw medication, 163 without (group A) and 253 with support of a headache nurse (group B). Both groups differed significantly in gender, age, type of medication and daily use of medication (Table 1). Although the absolute number of new headache