A systematic review and meta-analysis of data collected from observational cohort studies reveals several clinical and sociodemographic factors are predictors of chronic migraine.
The study, published in the International Headache Society’s Cephalalgia, looked at results of 11 prospective cohort studies that reported risk factors among patients suffering from episodic migraine. These risk factors were categorized as predictors of transformation from episodic migraine to chronic migraine. The 11 studies took place between 2004 and 2008 and covered 65,775 subjects. Both qualitative and quantitative analytic approaches were included in the review.
According to the authors, “An estimated 2.5% to 3.1% of people with episodic migraine develop chronic migraine” each year.
Individuals suffering from chronic migraine tend to have lower annual incomes, are less likely to have a full-time job, exhibit more comorbidities, and are more likely to have occupational disabilities compared with those with episodic migraine.
The pooled analysis of a fixed-effect model found “high evidence” for monthly headache day frequency ?10 (risk ratio [RR], 5.95; 95% CI, 4.75-7.46) and “moderate evidence” for depression (assessed by the Patient Health Questionnaire-9) (RR, 1.58; 95% CI, 1.35-1.85), monthly headache day frequency ?5 (RR, 3.18; 95% CI, 2.65-3.82), and annual household income ?$50,000 (RR, 0.65; 95%CI, 0.54-0.79) as predictors.
The analysis found “very low” evidence for cutaneous allodynia (RR, 1.40; 95% CI, 1.23-1.59) and medication overuse (RR, 8.82), although both slightly increased the risk of new onset chronic migraine,
Specifically, for the first time, they reported that “episodic migraine patients with monthly headache day frequency ?10 had a greater risk than monthly headache day frequency ?5 in transformation to chronic migraine.”
By identifying risk factors of the development of chronic migraine, the researchers hope to better understand the natural course of the disorder, in order to assist in selecting or designing interventions.
Other reported risk factors or predictors of chronic migraine in the selected studies included sex, body mass index, migraine symptom severity score, family headache history, and asthma.