Vitamin D for the management of asthma: Cochrane systematic review and meta-analysis

Background: Several clinical trials of vitamin D to reduce risk of asthma exacerbation and improve asthma control have been conducted in children and adults, but a meta-analysis restricted to double-blind randomised placebo-controlled trials of this intervention is lacking. Objectives: To evaluate the efficacy of administration of vitamin D in reducing asthma exacerbations treated with systemic corticosteroids (primary outcome) and improving asthma symptom control. Methods: Standard Cochrane Collaboration procedures were followed. Double-blind randomised placebo-controlled trials of vitamin D in children and adults with asthma evaluating exacerbation risk and/or asthma symptom control were included. Results: Seven trials involving a total of 435 children and two trials involving a total of 658 adults were included in the primary analysis. Administration of vitamin D reduced the rate of exacerbations requiring systemic corticosteroids (Rate Ratio 0.63, 95% CI 0.45 to 0.88; 680 participants; 3 studies), and decreased the risk of having at least one exacerbation requiring an emergency department visit and/or hospitalisation (Odds Ratio [OR] 0.39, 95% CI 0.19 to 0.78; 963 participants; 7 studies). Sub-group analysis to determine whether the effect of vitamin D on risk of severe exacerbation was modified by baseline vitamin D status was not performed, due to unavailability of suitably disaggregated data. Conclusions: Vitamin D is likely to prevent severe asthma exacerbation and reduce health care use by people with asthma. It is not yet clear whether these effects are confined to people with lower baseline vitamin D status. Further research is needed before definitive clinical recommendations can be made.