ase Control estimates that nearly one-third of African Americans are deficient in Vitamin D. Other groups at risk of Vitamin D deficiency include the elderly, the obese, pregnant and lactating women, and people who receive limited exposure to the sun.
The LSU study involved 81 patients, all of whom had either sleep problems or musculoskeletal pain either in the day or the evening, or both. Sixty five percent of the patients in the study were white, and 35% were African-American. All of the patients in the study group were diagnosed with a sleep disorder. Nearly three-quarters had obstructive sleep apnea, while others suffered from insomnia, or restless leg syndrome. All patients were evaluated for excessive daytime sleepiness using the Epworth Sleep Scale, a standard measurement. Their levels of Vitamin D were measured using blood tests.
The results of the study support a strong correlation between excessive daytime sleepiness and Vitamin D. They also indicate that race is a factor in the relationship between Vitamin D and daytime sleepiness. But the results were in some ways surprising and indicate a complicated relationship, particularly where race is concerned.
Here’s an overview of the most important findings:
- 65% of the study population was found to have a Vitamin D deficiency
- The patients with greater skin pigmentation had higher average levels of daytime sleepiness and lower average levels of Vitamin D, compared to those with less skin pigmentation
- African American patients made up 35% of the study population, but 55% of the group that were deficient in Vitamin D
- Only 6% of the group without a Vitamin D deficiency were African-American
- Among those with deficiencies of Vitamin D—under 20 mg/mL as measured by a blood test—there was no correlation between Vitamin D levels and daytime sleepiness. This is the opposite of what was expected based on prior research.
- An exception to this was found among African-American patients in the study group. Among those African-American patients with Vitamin D deficiency, there was a direct correlation between levels of Vitamin D and daytime sleepiness. Among these patients, higher Vitamin D levels were associated with higher levels of daytime sleepiness-the exact opposite of what was expected.
It is this last finding that is unexpected, and surprised researchers themselves, who expected to see lower levels of Vitamin D associated with higher levels of daytime sleepiness.
Why might this have been the case? Additional research clearly is needed to further explore the role that skin pigmentation may play in Vitamin D deficiency and its effect on sleep, and daytime sleepiness in particular. This was a small study, and larger-scale research may provide a clearer picture of this complicated relationship.
There are other important questions that arise. We can see an association between Vitamin D deficiency and daytime sleepiness, but we don’t have an understanding of cause and effect. Is Vitamin D deficiency directly responsible for excessive daytime sleepiness and other sleep problems? Or is poor sleep a consequence of other medical conditions associated with Vitamin D deficiency, such as chronic pain? What are the biological mechanisms by which Vitamin D—and a lack thereof—affect sleep functions in the body? There’s a lot we don’t yet know about the relationship between Vitamin D and sleep.
If you’re at risk for Vitamin D deficiency, talk to your doctor. Supplements, dietary changes, and safe and controlled exposure to sun can all help boost levels in the body. Making sure your body has sufficient levels of Vitamin D offers important health protections and, perhaps, a welcome boost of energy in place of daytime sleepiness.
Michael J. Breus, PhD
The Sleep Doctor™