Migraine prevalence, socioeconomic status, and social causation

Objective: To determine whether the known higher prevalence of migraine in lower household (HH) income groups is explained by a higher incidence rate or a lower remission rate. Methods: We used data from the American Migraine Prevalence and Prevention Study, a US national sample of 132,674 females (with a 64.3% response rate) and 124,665 males (with a 62.0% response rate) 12 years of age and older. Data were previously collected on migraine symptoms, onset age, and demographics. Previously validated methods applied to the American Migraine Prevalence and Prevention Study data were used to simulate a cohort study. Incidence and remission rates were estimated within 3 sex-specific HH income groups (<$22,500, $22,500-$59,999, and >=$60,000). The chi(2) test was used to determine whether the incidence or remission rates differed by HH income group as an explanation for differences in migraine prevalence by HH income. Results: Migraine prevalence increased as HH income decreased for females (chi(2), p < 0.01) and males (chi(2), p < 0.01). Differences were not explained by race and other known confounders. Variation in prevalence was explained, in large part, by a higher incidence rate in the lower HH income groups for both females (chi(2), p < 0.01) and males (chi(2), p < 0.01). Migraine remission rates did not differ by HH income. Conclusions: The higher incidence of migraine in lower HH income groups is compatible with the social causation hypothesis. Once initiated, migraine remission is independent of HH income. Onset and remission may have etiologically distinct causes.