Previously, the prevalence of vitamin D deficiency in migraine patients, as well as its link to migraine itself, had not been clearly reported.
Researchers at Ewha Women's University, Hallym University College of Medicine and Dongguk University in South Korea retrospectively assessed 157 first-visit migraine patients aged 37 to 45.6 years at the University Hospital of Hwaseong between January 2016 and May 2017.
They also took into consideration the patients' demographics, season, migraine sub-types and frequency, severity and impact, psychological and sleep variables, and climate factors, measuring their non-fasting serum vitamin D concentration to determine their vitamin D levels.
The researchers then found that 77.1% of the patients were vitamin D-deficient, and that this deficiency was more common in the spring and winter (when a respective 89.1% and 85.7% of patients were vitamin D-deficient) than in summer and autumn (72.4% and 61.7%, respectively).
They also reported that monthly headaches were 1.2 times more frequent in migraine patients who were vitamin D-deficient than in those who were not.
Furthermore, similar associations were "consistently noted" in subgroup analysis of both chronic migraine and episodic migraine.
While factors such as stress, dehydration and even MSG consumption are said to contribute to the incidence of headaches, especially amongst migraine patients, the effects of vitamin insufficiency and deficiency on such patients have not been extensively studied.
The researchers outlined the study's limitations, one of which was its relatively small sample size.
Additionally, the link between vitamin D deficiency and the number of days in a month the participants experienced headaches was statistically significant in both episodic and chronic migraine patients, but this was based on recall instead of assessment using a headache diary, which may have skewed the results.
The researchers also did not evaluate the patients vitamin D replacement by way of diet, medication or fortification.
However, the study's geographic and cultural components (high latitudes in Asia with no prominent sun-seeking habits) provided 'novel insights' into vitamin D's relationship with migraine in a location with a high vitamin D deficiency risk.
The researchers had also systematically assessed depression, anxiety and sleep quality, characteristics closely associated with migraine.
The study also adjusted for climate factors and seasonal variation that affected serum vitamin D levels.
The researchers concluded: "Our study found that a larger number of monthly days with headache is related to vitamin D deficiency among migraineurs.
"The vitamin D level may also be associated with the occurrence or impact of headache among migraineurs. Future studies should attempt to confirm the causal relationship between vitamin D deficiency and migraine."
Source: Journal of Clinical Neurology
"Effect of Vitamin D Deficiency on the Frequency of Headaches in Migraine"
Authors: Tae-Jin Song, et al.