title: Vitamin D supplementation to patients with frequent respiratory tract infections: a post hoc analysis of a randomized and placebo-controlled trial.
abstract: BACKGROUND
  Vitamin D is considered to be important for a healthy immune system. The aim of this study was to test the hypothesis that vitamin D supplementation reduces number of respiratory tract infections (RTIs) and prolong the time to the first RTI in adult patients with frequent RTIs.
  
  
  METHODS
  We performed a post hoc analysis of a randomized, placebo-controlled and double-blinded study, where adult patients with a high burden of RTIs were randomized to placebo or vitamin D (4000 IE/day for 1 year, n = 124 in the per protocol cohort presented here).
  
  
  RESULTS
  Vitamin D supplementation increased the probability to stay free of RTI during the study year (RR 0.64, 95% CI 0.43-0.94). Further, the total number of RTIs was also reduced in the vitamin D-group (86 RTIs) versus placebo (120 RTIs; p = 0.05). Finally, the time to the first RTI was significantly extended in the vitamin D-group (HR 1.68, 95% CI 1.03-2.68, p = 0.0376).
  
  
  CONCLUSIONS
  Vitamin D supplementation was found to significantly increase the probability of staying infection free during the study period. This finding further supports the notion that vitamin D-status should be monitored in adult patients with frequent RTIs and suggests that selected patients with vitamin D deficiency are supplemented. This could be a safe and cheap way to reduce RTIs and improve health in this vulnerable patient population. The original trial was registered at http://www.clinicaltrials.gov (NCT01131858).
authors: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet and Karolinska University Hospital Huddinge, 141 86, Stockholm, Sweden. peter.bergman@ki.se.
authors: Peter
authors: P
authors: Bergman
authors: Division of Clincal Immunology, Karolinska Institutet and Karolinska University Hospital Huddinge, 141 86, Stockholm, Sweden. anna-carin.norlin@karolinska.se.
authors: Anna-Carin
authors: AC
authors: Norlin
authors: Infectious Disease Clinic, Karolinska University Hospital, 141 86, Stockholm, Sweden. susanne.hansen@karolinska.se.
authors: Susanne
authors: S
authors: Hansen
authors: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet and Karolinska University Hospital Huddinge, 141 86, Stockholm, Sweden. linda.bjorkhem-bergman@ki.se.
authors: Linda
authors: L
authors: Björkhem-Bergman
mesh_terms: D000328:Adult; D015331:Cohort Studies; D019587:Dietary Supplements; D006801:Humans; D010919:Placebos; D012141:Respiratory Tract Infections / Q000517:prevention & control*; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D010919:Placebos; D014807:Vitamin D