Vitamin D Concentrations and Obstructive Sleep Apnea in a Multicenter Cohort of Older Males

Rationale: Seasonal nadirs in 25-hydroxyvitamin D (25[OH] D) concentrations overlap with increased incidence and severity of obstructive sleep apnea (OSA) in winter. We hypothesized that, because lower 25(OH) D concentrations might lead to upper airway muscle dysfunction, low 25(OH) D would be associated with higher apnea-hypopnea index (AHI), a measure of OSA severity. Objectives: To determine if lower 25(OH) D concentration is associated with greater prevalence and increased severity of OSA, independent of established OSA risk factors. Methods: Using unconditional logistic regression, we performed a cross-sectional analysis in the Outcomes of Sleep Disorders in Older Men study, which included in-home overnight polysomnography, serum 25(OH) D measurement, and collection of demographic and comorbidity data. The primary outcome was severe sleep apnea, as defined by AHI of 30/h or more. Measurements and Main Results: Among 2,827 communitydwelling, largelywhite (92.2%), elderly (aged 76.4 +/- 5.5 yr [mean +/- SD]) males, mean 25(OH) D concentration was 28.8 (+/- 8.8) ng/ml. Subjects within the lowest quartile of 25(OH) D (6-23 ng/ml) had greater odds of severe sleep apnea in unadjusted analyses (odds ratio = 1.45; 95% confidence interval = 1.02-2.07) when compared with the highest 25(OH) D quartile (35-84 ng/ml). However, further adjustment for established OSA risk factors strongly attenuated this association (multivariable adjusted odds ratio = 1.05; 95% confidence interval = 0.72-1.52), with body mass index and neck circumference as the main confounders. There was also no evidence of an independent association between lower 25(OH) D levels and increased odds ofmild (AHI = 5.0-14.9/h) or moderate (AHI = 15.0-29.9/h) sleep apnea. Conclusions: Amongcommunity-dwellingolder men, the association between lower 25(OH) D and sleep apnea was largely explained by confounding by larger body mass index and neck circumference.