Vitamin D deficiency in patients referred for evaluation of obstructive sleep apnea

Abstract

Study Objectives: A recent study reported an association between obstructive sleep apnea (OSA) and low Vitamin D levels. In this study, we measured Vitamin D levels in patients referred for evaluation of suspected OSA and sought to identify associated risk factors for Vitamin D deficiency. Our objective was to determine whether evaluations of patients with suspected OSA should include routine screening for Vitamin D deficiency. Methods: Using a cross-sectional study design, we measured Vitamin D levels in consecutively enrolled patients referred for an OSA evaluation to Dr. Lutfi Kirdar Kartal Training and Research Hospital in Istanbul, Turkey. We conducted full-night polysomnography and compared Vitamin D levels both between patients with OSA and patients without OSA and across the various severity levels of OSA. We evaluated the association between Vitamin D levels and various clinical and demographic characteristics, including the apnea-hypopnea index and body mass index. Results: From April 2014 to June 2015, 195 patients were referred for OSA evaluation. Of these, 181 patients (93%) consented to participate and underwent full polysomnography and measurement of Vitamin D levels. The mean ± standard deviation age was 49 ± 12 years and body mass index of 31 ± 6 kg/m2. Polysomnography led to the diagnosis of OSA in 162 of the patients (89.5%): 52 (32%) were categorized as having mild OSA, 38 (23.5%) as having moderate OSA, and 72 (44.5%) as having severe OSA. Vitamin D level was 15.5 ± 11.6 ng/mL (95% confidence interval; 13-17 ng/mL) and 134 patients (74%) met the criterion for Vitamin D deficiency (< 20 ng/mL). Sex, Vitamin D levels, and percentage of patients with Vitamin D deficiency were similar in patients with and without OSA (P >.05). Vitamin D levels were similar across OSA severity categories (P =.68). We found no association between Vitamin D levels and the apnea-hypopnea index or body mass index. Conclusion: A large proportion of patients referred for OSA evaluation had Vitamin D deficiency. Vitamin D levels did not differ by OSA diagnosis status or severity. Patients referred for polysomnography should undergo routine screening for Vitamin D deficiency as well as clinically indicated treatment to prevent associated comorbidities.