Sleep Apnea & Vitamin D

A systematic review and meta-analysis published in Sleep & Breathing evaluated the association between serum levels of 25-hydroxyvitamin D (25OHD) and obstructive sleep apnea syndrome (OSAS). Twenty-four studies were found eligible for this review, including 15 case-control studies and 9 cross-sectional studies, involving a total of 2640 people with OSAS and 933 healthy participants (controls) for comparison. The majority of studies were conducted among adults, but 4 of the studies enrolled a pediatric population. Of the included studies, 5 were at low risk of bias, 8 at medium risk, and 11 at high risk (largely because of confounding). 

While no significant association was observed for mild OSAS, significantly lower 25OHD levels were observed for people with moderate OSAS (-3.36ng/mL), and an even greater difference among people with severe OSAS (-6.38ng/mL). A significantly lower 25OHD was observed when all studies were pooled among both adults (-4.76ng/mL) and children (-7.65ng/mL). When stratified by weight (most participants had obesity), a significant relationship was still observed among people with a healthy weight and with obesity (but not overweight). Overall, the severity of OSAS was the most important predictor of 25OHD levels.

Vitamin D has been suggested to potentially influence OSAS through multiple mechanisms, including inhibition of inflammatory cytokines, support for the activity of upper airway muscles, and modulation of brainstem receptors which influence sleep. It’s also possible that people with OSAS are more at risk for low vitamin D levels, as a consequence of limited time outside, daytime sleepiness, etc. While large controlled trials of vitamin D as an intervention for OSAS have not been conducted, there is evidence that reduced 25OHD levels drive insulin resistance, which in turn promotes OSAS.