Vitamin D deficiency and daytime sleepiness

In the last few years, it seems that vitamin D deficiency was present in many patients I saw in clinic. Vitamin D deficiency has been found to be associated with chronic pain conditions like fibromyalgia. Vitamin D deficiency is also associated with fatigue and sleepiness. Dr. McCarty et al at LSU did a study looking at vitamin D levels and subjective sleepiness in patients referred to his sleep clinic. Interestingly, the results showed that vitamin D deficiency was associated with more subjective sleepiness, but only in black patients. The same effect was not seen in white patients. The author did not have an explanation for the racial differences. It could be that the black patients in this study had more obstructive sleep apnea - this sleep disorder was not measured during this study.