Background and purpose: The risk of vitamin D deficiency varies with the season. The frequency of vitamin D deficiency in migraine patients and its association with migraine are unclear.
Methods: We retrospectively evaluated first-visit migraine patients between January 2016 and May 2017, and investigated the demographics, season, migraine subtypes, frequency, severity, and impact of migraine, psychological and sleep variables, climate factors, and vitamin D levels. The nonfasting serum 25-hydroxyvitamin D concentration was measured to determine the vitamin D level, with deficiency of vitamin D defined as a concentration of <20 ng/mL.
Results: In total, 157 patients with migraine aged 37.0±8.6 years (mean±standard deviation) were analyzed. Their serum level of vitamin D was 15.9±7.4 ng/mL. Vitamin D deficiency was present in 77.1% of the patients, and occurred more frequently in spring and winter than in summer and autumn (89.1%, 85.7%, 72.4%, and 61.7%, respectively; p=0.008). In multivariate Poisson regression analysis, monthly headache was 1.203 times (95% confidence interval=1.046-1.383, p=0.009) more frequent in patients with vitamin D deficiency than in those without deficiency after adjusting for demographics, season, migraine subtype, depression, anxiety, and sleep quality. These associations were consistently noted in subgroup analysis of episodic migraine (odds ratio=1.266, p=0.033) and chronic migraine (odds ratio=1.390, p=0.041).
Conclusions: Our study found that a larger number of monthly days with headache was related to vitamin D deficiency among migraineurs. Future studies should attempt to confirm the causal relationship between vitamin D deficiency and migraine.
Keywords: migraine; seasonal variation; summer; vitamin D; winter.
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