Association between vitamin D status and asthma control: A meta-analysis of randomized trials.
Respir Med. 2019 Apr ;150:85-94. Epub 2019 Feb 21. PMID: 30961957
BACKGROUND: There is a controversy in terms of the efficacy of vitamin D supplementation in improving asthma symptom control. Moreover, whether there is a difference in the treatment effect with respect to baseline vitamin D status remains unknown. This meta-analysis was to assess the correlations of vitamin D status with asthma-related respiratory outcomes.
METHODS: PubMed, EMBASE, and Cochrane Library were searched for randomized controlled trials of vitamin D supplementation in patients with asthma. Primary outcomes were the rate of asthma exacerbation and predicted percentage of forced expiratory volume in first second (FEV%). Secondary outcomes were asthma control test (ACT) scores, fractional exhaled nitric oxide (FeNO), interleukin-10 (IL-10) and adverse events.
RESULTS: A total of 14 randomized controlled trials (1421 participants) fulfilled the inclusion. Vitamin D supplementation was associated with a significant reduction in the rate of asthma exacerbation by 27% (RR: 0.73 95%Cl (0.58-0.92)). In subgroup analysis, the protective effect of exacerbation was restricted in patients with vitamin D insufficiency (vitamin D < 30 ng/ml) (RR: 0.76 95%Cl (0.61-0.95)). An improvement of FEV% was demonstrated in patients with vitamin D insufficiency and air limitation (FEV% < 80%) (MD: 8.3 95%Cl (5.95-10.64). No significant difference was observed in ACT scores, FeNO, IL-10 and adverse events.
CONCLUSIONS: Vitamin D supplementation reduced the rate of asthma exacerbation, especially in patients with vitamin D insufficiency. Additionally, the benefit of vitamin D had a positive effect on pulmonary function in patients with air limitation and vitamin D insufficiency.