title: Vitamin D, asthma prevalence and asthma exacerbations: a large adult population-based study.
abstract: BACKGROUND
  The impact of low vitamin D status on asthma, asthma morbidity and control is unclear. We aimed to investigate in adults the associations between serum 25-hydroxyvitamin D level and prevalent asthma as well as asthma exacerbations.
  
  
  METHODS
  A cohort of Israeli adults aged 22-50 years with documented vitamin D status were extracted from Clalit Health Services (HMO) between July 1, 2008 and July 1, 2012. Among this population, those with physician-diagnosed asthma and asthma exacerbations were identified. Asthma exacerbations were defined as any of the following: prescription for oral corticosteroids, >5 prescriptions for short acting beta agonists and more than four visits to a physician for asthma. Logistic regression models assessed the associations between vitamin D and both asthma and asthma exacerbations.
  
  
  RESULTS
  Approximately 308 000 members with at least one vitamin D measurement were included in the cohort. Among them, 6.9% (21 237) had physician-diagnosed asthma vs 5.7% in the general population. Serum 25-OHD levels across both groups were similar. However, among those with vitamin D deficiency, the odds of having an exacerbation were 25% greater compared to those with levels in the normal range. This association remained significant after controlling for known confounders.
  
  
  CONCLUSIONS
  While there was no significant association between vitamin D status and physician-diagnosed asthma, there was a strong association with asthma exacerbations. The presented evidence supports vitamin D screening in the subgroup of asthmatics that are uncontrolled and experience recurrent exacerbations.
authors.affiliation: Allergy and Clinical Immunology Unit, Meir Medical Center, Kfar Saba, Israel; Sackler Faculty of Medicine, Tel Aviv University, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Confino-Cohen
authors.forename: I
authors.initials: I
authors.lastname: Brufman
authors.forename: A
authors.initials: A
authors.lastname: Goldberg
authors.forename: B S
authors.initials: BS
authors.lastname: Feldman
mesh_terms: D000328:Adult; D001249:Asthma / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D015995:Prevalence; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood*; D014808:Vitamin D Deficiency / Q000150:complications; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: asthma; asthma control; asthma exacerbation; vitamin D; vitamin D deficiency