Introduction and objectives Several clinical trials of vitamin D to prevent 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. We conducted a Cochrane systematic review and meta-analysis 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; high quality evidence), 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; number needed to treat for one additional person to experience a beneficial outcome (NNTB), 27; 963 participants; 7 studies; high quality evidence). There was no effect of vitamin D on % predicted forced expiratory volume in one second (Mean Difference [MD] 0.48, 95% CI: −0.93 to 1.89; 387 participants; 4 studies; high quality evidence) or Asthma Control Test scores (MD −0.08, 95% CI: −0.70 to 0.54; participants = 713; studies = 3; high quality evidence). Administration of vitamin D did not influence the risk of serious adverse events (OR 1.01, 95% CI: 0.54 to 1.89; 879 participants; 5 studies; moderate quality evidence). No participant in any included trial suffered a fatal asthma exacerbation.
Conclusions Meta-analysis of a modest number of trials in patients with predominantly mild to moderate asthma suggests that vitamin D is likely to reduce the risk of severe asthma exacerbation and reduce health care use.
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