A recent study published in the journal Nutrients found low vitamin D levels were independently related to sleep disturbance in hemodialysis patients.
Vitamin D receptors are located throughout areas of the brain that are considered to play a role in the initiation and maintenance of sleep. This finding has led researchers to hypothesize that vitamin D affects sleep quality.
Multiple studies have shown low vitamin D levels are linked to sleep disorders, such as obstructive sleep apnea. Furthermore, an uncontrolled trial of vitamin D supplementation in 1500 patients over a two-year span discovered that maintaining a vitamin D status between 60-80 ng/ml produced normal sleep in most patients, regardless of their previous sleep disorder.
Since sleep disturbance is a frequent and serious complication of hemodialysis (HD), researchers from China recently conducted a study to evaluate the relationship between vitamin D status and sleep disturbance in HD patients.
The researchers assessed the vitamin D levels and sleep quality of 141 HD patients and 117 healthy individuals.
Here is what they found:
- Of the 141 HD patients, 88 (62.4%) had sleep disturbance.
- HD patients had significantly lower vitamin D levels compared to the healthy individuals (22.64 ng/ml and 27.52 ng/ml, respectively).
- HD patients with sleep disturbance had significantly lower vitamin D levels than those without sleep disturbance (15.6 ng/ml and 34.2 ng/ml, respectively; p < 0.001).
- After adjusting for various confounding factors, vitamin D levels were independently associated with sleep disturbance in HD patients (OR 9.897, 95% CI 3.356–29.187, p < 0.001).
The researchers concluded,
“We found that low serum levels of vitamin D were significantly associated with sleep disturbance in HD patients, which is similar to the findings of previous studies in elderly adults and patients with [systemic lupus erythematosus].”
They went on to state,
“Our finding might have important implications in providing novel proposals for the prevention and treatment of sleep disturbance in HD patients.”
There are a few limitations to consider. First, the study did not account for the effects of dietary intake and lifestyle on vitamin D status. Therefore, individuals with healthier and more active lifestyles may have had higher vitamin D levels, meaning the better sleep quality may be attributed to healthier lifestyles. Also, the researchers used the Pittsburgh Sleep Quality Index (PSQI), a self-administered questionnaire, to assess sleep quality. The PSQI fails to objectively evaluate sleep, and thus, errors in self-reported sleep quality may have skewed the results. Lastly, the study included the Han Chinese population, which limits the generalizability to other populations.
Randomized controlled trials are needed to prove whether vitamin D supplementation directly improves sleep quality among HD patients.
Tovey, A. & Cannell, JJ. Low vitamin D levels linked to troubles sleeping in hemodialysis patients. The Vitamin D Council Blog & Newsletter, February 28, 2017.