Analysis of outcome predictors of migraine towards chronicity.

Long-term migraine evolution is still undefined. The poorest outcome is the transformation from episodic attacks to a pattern of daily attacks or continuous headache with intermittent attacks. We called these cases "chronic migraine". The aim of our study was to investigate whether some clinical variables contributed to migraine chronicity. We interviewed 50 patients with chronic migraine from 2 to 15 years and 90 patients with episodic migraine matched for sex and age as a control group. Univariate analysis revealed two correlations with a chronic outcome: (1) In the control group a significantly higher number of women took oral contraceptives. (2) In the group who developed chronic migraine, there were a greater number of smokers, without reaching statistical significance. The stepwise multiple logistic regression method showed that these two variables influence the prognosis with a maximum likelihood estimate of 65%, hence not much higher than random probability.