Conclusions Vitamin D supplementation  was safe and it protected against acute respiratory tract infection overall .
Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .
Vitamin D3 supplementation in patients with chronic obstructive pulmonary disease (ViDiCO): a multicentre, double-blind, randomised controlled trial.
BACKGROUND Patients with chronic obstructive pulmonary disease ( COPD ) often have vitamin D deficiency , which is associated with increased susceptibility to upper respiratory infection-a major precipitant of exacerbation . Multicentre trials of vitamin D supplementation for prevention of exacerbation and upper respiratory infection in patients with COPD are lacking . We therefore investigated whether vitamin D3 ( colecalciferol ) supplementation would reduce the incidence of moderate or severe COPD exacerbations and upper respiratory infections . METHODS We did a r and omised , double-blind , placebo-controlled trial of vitamin D3 supplementation in adults with COPD in 60 general practice s and four Acute National Health Service Trust clinics in London , UK . Patients were allocated to receive six 2-monthly oral doses of 3 mg vitamin D3 or placebo over 1 year in a 1:1 ratio using computer-generated permuted block r and omisation . Participants and study staff were masked to treatment assignment . Co primary outcomes were time to first moderate or severe exacerbation and first upper respiratory infection . Analysis was by intention to treat . A prespecified subgroup analysis was done to assess whether effects of the intervention on the co primary outcomes were modified by baseline vitamin D status . This trial is registered with Clinical Trials.gov , number NCT00977873 . FINDINGS 240 patients were r and omly allocated to the vitamin D3 group ( n=122 ) and placebo group ( n=118 ) . Vitamin D3 compared with placebo did not affect time to first moderate or severe exacerbation ( adjusted hazard ratio 0·86 , 95 % CI 0·60 - 1·24 , p=0·42 ) or time to first upper respiratory infection ( 0·95 , 0·69 - 1·31 , p=0·75 ) . Prespecified subgroup analysis showed that vitamin D3 was protective against moderate or severe exacerbation in participants with baseline serum 25-hydroxyvitamin D concentrations of less than 50 nmol/L ( 0·57 , 0·35 - 0·92 , p=0·021 ) , but not in those with baseline 25-hydroxyvitamin D levels of at least 50 nmol/L ( 1·45 , 0·81 - 2·62 , p=0·21 ; p=0·021 for interaction between allocation and baseline serum 25-hydroxyvitamin D status ) . Baseline vitamin D status did not modify the effect of the intervention on risk of upper respiratory infection ( pinteraction=0·41 ) . INTERPRETATION Vitamin D3 supplementation protected against moderate or severe exacerbation , but not upper respiratory infection , in patients with COPD with baseline 25-hydroxyvitamin D levels of less than 50 nmol/L. Our findings suggest that correction of vitamin D deficiency in patients with COPD reduces the risk of moderate or severe exacerbation . FUNDING UK National Institute for Health Research
Conclusions Vitamin D supplementation  was safe and it protected against acute respiratory tract infection overall .
Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .