Introduction:
This study evaluated the association between iron deficiency anemia (IDA) and migraine and investigated the effects of iron supplementation, and comorbid conditions, including cardiovascular, respiratory, hepatic, endocrine, metabolic, and other diseases on migraine development.

Material and methods:
All study subjects aged ≥20 years with newly diagnosed IDA in the Taiwan National Health Insurance Database during 2000–2012 were enrolled. We matched IDA and non-IDA subjects according to age and sex at a 1:2 ratio. Our primary outcome was diagnosis of migraine, and the patients were monitored until the end of 2013. A Cox proportional hazards regression model was used to evaluate the risk of migraine events in IDA.

Results:
The cumulative incidence of migraine in patients with IDA was 5.82 per 1,000 person-years, which was higher than that in the comparison group (3.99 per 1,000 person-years) during the follow-up period (log-rank test, p < 0.001). After controlling for potentially confounding factors, the risk of migraine was higher in the IDA group compared with the non-IDA group (the adjusted hazard ratio = 1.68, 95% CI = 1.51−1.87, p < 0.001). Female and ≤50 year-old IDA patients with or without iron supplementation use had an increased incidence of migraine (p < 0.05).

Conclusions:
Our study provided additional evidence of an increased risk of migraine in patients with IDA. We also found that females and ≤50 year-old IDA patients with or without iron supplementation use had an increased risk of migraines.