Vitamin D does not improve lung function decline in COPD: a meta-analysis.

Abstract

Vitamin D deficiency plays an important role in chronic obstructive pulmonary disease (COPD). However, the effects of vitamin D supplementation on lung function decline in COPD were inconsistently reported and a meta-analysis is thus needed. Eligible cohort and randomized controlled trials (RCTs) were searched from databases including PubMed, Embase, and Web of Science. Pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated in a random or fixed effects model. Eight studies reaching the inclusion criteria and involving 687 COPD patients were included. Pooled effect size showed vitamin D treatment resulted in no significant improvements in FEV1 (SMD: 0.38, 95% CI: -0.13 to 0.88, p= 0.144), FVC (SMD: 0.55, 95% CI: -0.49 to 1.58, p=0.299), and FEV1/FVC (SMD: 0.00, 95% CI: -0.27-0.27, p=0.995) in COPD patients. Subgroup analysis revealed neither short-term (<6 months) (SMD: 0.10, 95% CI: -0.17 to 0.37, p=0.479) nor long-term (≥6 months) (SMD: 0.52, 95% CI: -0.23 to 1.27, p=0.172) vitamin D exposure could significantly benefit lung function decline in COPD. This meta-analysis shows neither short-term nor long-term additional supplementation of vitamin D can benefit the lung function decline in COPD. Moreover, large scale RCTs focusing on COPD smokers with low level of vitamin D should be considered.