Chronic migraine, comorbidity, and socioeconomic deprivation: cross-sectional analysis of a large nationally representative primary care database.

Background: Chronic migraine is common but there is limited knowledge on associated comorbidities.

Objectives: To examine mental and physical comorbidities in chronic migraine and the influence of socioeconomic status in a large, nationally representative dataset.

Design: Analysis of cross-sectional primary healthcare data from 1,468,404 adults in Scotland. Chronic migraine, 31 other physical conditions, and seven mental health conditions we examined. Prevalence rates were standardized by age groups, sex, and socioeconomic deprivation, and adjusted odds ratio (aOR) and 95% confidence intervals (CI) calculated for those with chronic migraine compared with those without.

Results: Chronic migraine patients had more conditions, with the biggest difference found for five or more conditions (chronic migraine 11.7% vs. controls 4.9%; aOR 3.00; 95% CI 2.78-3.22). Twenty-five of the 31 physical conditions were significantly more prevalent in the chronic migraine group. The biggest difference was for chronic pain (aOR 4.33; 95% CI 4.12-4.55). For mental health conditions, the biggest differences were for anxiety (aOR 2.95; 95% CI 2.76-31.5) and depression (aOR 2.94; 95% CI 2.81-3.08). Increasing deprivation was associated with more severe and complex comorbidity (five or more conditions), and with more combined mental and physical comorbidity in the chronic migraine group.

Conclusions: In a large nationally representative sample in primary care, comorbidity was most common in those with chronic migraine compared with standardized controls, and this was exacerbated by living in areas of higher deprivation.