Vitamin D and asthma occurrence in children: A systematic review and meta-analysis

The association between serum 25-Hydroxyvitamin D (25-OHD) level and asthma occurrence in children was controversial.The Pubmed, Ovid Medline, Embase, Cochrane Library were systematically searched up to April 13th 2020. All the study measured the serum 25-OHD level in children, or classified the children based on the 25-OHD level into severe vitamin D deficiency, insufficient deficiency and comparing the prevalence of asthma in childhood were included in our study.A total of 35 studies were included in our meta-analysis. Among them, 24 studies were included for analyzing the association between 25-OHD level and asthma, and 12 studies evaluated the treatment effect of vitamin D.The children with asthma (5711 participants) had significant lower 25-OHD level than children without asthma (21,561 participants) (21.7 ng/ml versus 26.5 ng/ml, SMD = -1.36, 95% = -2.40--0.32, P = 0.010). Besides, the children with asthma treated with vitamin D supplement had a significantly lower recurrence rate than the placebo group (18.4% versus 35.9%, RR = 0.35, 95%CI = 0.35-0.79, P = 0.002).Children with asthma had a lower 25-OHD level than healthy children. Vitamin D supplement could decrease the asthma recurrence rate in the follow-up years.This study implies that lower 25-OHD may cause asthma in childhood.