title: Vitamin D Deficiency in Patients Referred for Evaluation of Obstructive Sleep Apnea.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Banu
authors.initials: B
authors.lastname: Salepci
authors.affiliation: İstanbul, Koç University Medical Faculty, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Benan
authors.initials: B
authors.lastname: Caglayan
authors.affiliation: University of California, San Francisco, San Francisco General Hospital, Division of Pulmonary and Critical Care Medicine, San Francisco, California.
authors.forename: Payam
authors.initials: P
authors.lastname: Nahid
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Elif Torun
authors.initials: ET
authors.lastname: Parmaksiz
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Nesrin
authors.initials: N
authors.lastname: Kiral
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Ali
authors.initials: A
authors.lastname: Fidan
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Sevda Sener
authors.initials: SS
authors.lastname: Comert
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Coskun
authors.initials: C
authors.lastname: Dogan
authors.affiliation: University of Medical Sciences İstanbul, Kartal Dr. Lutfi Kirdar Teaching and Research Hospital, Chest Diseases Clinic, Istanbul, Turkey.
authors.forename: Gulten Aktin
authors.initials: GA
authors.lastname: Gungor
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012017:Referral and Consultation; D012307:Risk Factors; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000097:blood / Q000150:complications* / Q000175:diagnosis; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications* / Q000175:diagnosis
keywords: obstructive sleep apnea; vitamin D deficiency; vitamin D level