US researchers propose the hypothesis that sleep disorders have become epidemic because of widespread vitamin D deficiency.
The scientists’ observation that sleep seemed to improve with vitamin D supplementation led to a two year uncontrolled clinical trial of vitamin D supplementation for 1,500 patients with neurologic complaints, who also had evidence of abnormal sleep (1). The study results showed that patients’ neurologic symptoms and sleep improved, but only through maintaining a narrow range of 25(OH) vitamin D3 blood levels of 60–80 ng/ml. The sleep difficulties produced by vitamin D levels below 50 returned, in the same form, as the level rose above 80 ng/ml, suggesting a narrower range of normal vitamin D levels for sleep than those published for bone health. According to the researchers, these clinical observations need to be confirmed by extended intervention studies.
Comparisons of brain regions associated with sleep-wake regulation and vitamin D-target neurons in the brain (diencephalon and several brainstem nuclei) suggest direct central effects of vitamin D on sleep. Because sleep disorders are known to increase the incidence and severity of hypertension, obesity, diabetes, heart disease, stroke, depression, and chronic pain, the observation of a clinical and anatomic link between sleep and vitamin D not only suggests a new treatment for sleep disorders: It also suggests a need for investigation of careful management of vitamin D levels to prevent or improve several medical conditions that have become epidemic in developed countries at the same time, the researchers added.