Association between blood vitamin D and myocardial infarction: A meta analysis including observational studies

Background: The association between blood vitamin D levels and the risk of myocardial infarction (MI) is controversial. This meta-analysis aimed to describe the relationship between MI risk and blood vitamin D levels. Methods: Online databases were searched in PubMed, EMBASE and Web of science till February 2017 for observational studies in relation to reporting the vitamin D levels in MI cases and non-MI controls. The weighted mean difference (WMD) or odds ratio (OR), with 95% confidence interval (CI), were calculated to evaluate the relationship between MI risk and blood vitamin D levels. Results: Eight observational studies with 9913 individuals, consisted of 3411 MI patients and 6502 non-MI controls, were included in our study. The pooled results revealed that blood vitamin D levels were significantly lower in MI patients when compared with non-MI controls (WMD = -03.40; 95% CI: -5.87 to -0.92, P = 0.007). Subgroup analyses indicated MI patients were also associated with lower levels of blood vitamin D in America and Asia. Furthermore, when compared to non-MI controls, sufficient blood vitamin D appeared to protect against the occurrence of MI (OR = 0.44; 95% CI: 0.25 to 0.76, P = 0.004) in MI patients. Subgroup analyses also showed that sufficient blood 25(OH)D levels was a protective factor for MI in America and Asia. Conclusions: Present study suggested that the levels of blood 25(OH)D were significant lower in MI patients, especially in America and Asia, and sufficient blood vitamin D levels might protect against the occurrence of MI.