Data were analyzed using STATA software; odds ratios (OR) and confidence intervals (CI) were calculated using fixed or random effects models.



STATA
We retrieved studies from the PubMed, Web of Science, Ovid, and China National Knowledge Infrastructure databases. 
PubMed
We retrieved studies from the PubMed, Web of Science, Ovid, and China National Knowledge Infrastructure databases. 
Web of Science
We retrieved studies from the PubMed, Web of Science, Ovid, and China National Knowledge Infrastructure databases. 
Ovid
We retrieved studies from the PubMed, Web of Science, Ovid, and China National Knowledge Infrastructure databases. 
China National Knowledge Infrastructure databases