Vitamin D supplementation to prevent asthma exacerbations: a systematic review and meta-analysis of individual participant data.
Level 1 - systematic review of randomized trials
Systematic review and individual participant data meta-analysis of randomized controlled trials
PubMed 28986128 · doi:10.1016/S2213-2600(17)30306-5
What was done
A systematic review and individual participant data (IPD) meta-analysis of double-blind, placebo-controlled randomized controlled trials (RCTs) evaluating vitamin D2 or D3 supplementation in people with asthma. Databases were searched up to October 26, 2016. The primary outcome was the incidence of asthma exacerbations requiring treatment with systemic corticosteroids, analyzed using mixed-effects regression models adjusted for age and sex and clustered by study. Subgroup analyses evaluated effect modification by baseline 25-hydroxyvitamin D (25[OH]D) status and clinical characteristics.
What was found
Individual participant data were analyzed from 7 RCTs comprising 955 participants (6 trials at low risk of bias, 1 unclear). Vitamin D supplementation significantly reduced the rate of asthma exacerbations requiring systemic corticosteroids (adjusted incidence rate ratio [aIRR] 0.74, 95% CI 0.56–0.97; p=0.03; I²=0.0%). There were no significant differences in the proportion of participants with at least one exacerbation or time to first exacerbation. A significant reduction in exacerbation rate was observed in patients with baseline 25(OH)D <25 nmol/L (aIRR 0.33, 95% CI 0.11–0.98; p=0.046; n=92 across 3 trials), but not in those with higher baseline levels (aIRR 0.77, 95% CI 0.58–1.03; p=0.08; n=764 across 6 trials); however, the test for interaction was not statistically significant (p_interaction = 0.25).
Why it matters
This IPD meta-analysis demonstrates that vitamin D supplementation reduces the overall rate of severe asthma exacerbations requiring systemic steroids, though it does not provide definitive evidence that efficacy differs significantly across patient subgroups.
Limits
Individual participant data were unavailable for one eligible RCT (123 participants). The sample size for the severely vitamin D-deficient subgroup (<25 nmol/L) was small (n=92), limiting power to confirm subgroup-treatment interactions. The abstract reports no long-term safety data or lung function outcomes.
Cited by
- partial Having sufficient vitamin D has been shown to improve asthma.