A recent study published by the Current Vascular Pharmacology journal found that individuals with obstructive sleep apnea had lower vitamin D levels compared to healthy individuals. Additionally, patients were more likely to have more severe sleep apnea if they were vitamin D deficient.
Obstructive sleep apnea syndrome (OSAS) occurs when one’s breathing patterns become disrupted during sleep due to obstruction of the upper airway. This obstruction results from relaxation of the muscles lining the throat. Individuals who have hypertension, diabetes, are overweight, male or have a large neck circumference are more likely to develop OSAS.
Those with OSAS experience repetitive periods of shallow or paused breathing during their sleep cycle, resulting in a lack of oxygen. This causes sleep disturbances, leading to feelings of fatigue, impaired memory and diminished ability to complete tasks efficiently.
Researchers theorize vitamin D may play a role in the pathogenesis of OSAS. Both animal and in vitro studies have found hypoxia (lack of oxygen reaching the tissues) stimulates inflammatory pathways. Vitamin D helps reduce inflammation in the body by suppressing several proinflammatory molecules. Additionally, vitamin D has been shown to improve muscle function, a key component in OSAS. However, research evaluating the role of vitamin D in OSAS remains inconclusive; therefore, researchers recently aimed to determine whether vitamin D status may impact sleep characteristics among patients with OSAS.
A total of 169 individuals were included in the study, 139 of which had OSAS (cases) and 30 did not have the disorder (controls). All participants had their vitamin D levels measured and received polysomnography and pulmonary function testing to evaluate sleep apnea severity. Polysomnography is a sleep study used to diagnose sleep disorders. Pulmonary function tests measure how well the lungs function at inhaling and exhaling air and transferring oxygen in the blood.
Here is what the researchers found:
- A total of 80% of individuals with sleep apnea were men.
- OSAS patients were significantly older and had a higher BMI (p = 0.002 and p < 0.001, respectively).
- Those with OSAS had lower vitamin D levels than controls (17.8±7.8 vs 23.9±12.4 ng/ml, p = 0.019).
- Vitamin D status was negatively associated with OSAS patient’s ability to transition between sleep stages (p = 0.028).
- Low vitamin D status was associated with more episodes of shallow breathing and pauses between breathing (p = 0.045).
- Low vitamin D status was associated with increased hypoxia (p=0.011) and decreased oxyhaemoglobin saturation (p = 0.041). Oxyhaemoglobin saturation refers to the amount of oxygen bound to hemoglobin, a protein that transports oxygen in the red blood cells.
- Higher vitamin D status was associated with increased average oxyhaemoglobin saturation during sleep (p = 0.033), increased breathing capacity (p = 0.037) and oxygen partial pressure (p = 0.029). Oxygen partial pressure measures the amount of oxygen through arterial blood. Those with OSAS experience decreased ability to move oxygen from the lungs into the blood.
The researchers concluded,
“Vit D levels were lower in OSAS patients compared with non-apnoeic controls. Several indices of OSAS severity also correlated with Vit D levels.”
As always, it is important to note the limitations of the study. The cross sectional study design and small number of controls in comparison to the cases decreased the strength of these findings. In order to determine whether vitamin D supplementation may provide a treatment effect on patients with OSAS, randomized controlled trials are needed.
Sturges, M. & Cannell, JJ. Vitamin D status linked with severity of obstructive sleep apnea in adults. The Vitamin D Council Blog & Newsletter, 8/2017.