Lower Vitamin D Status Is Associated with an Increased Risk of Ischemic Stroke: A Systematic Review and Meta-Analysis

Abstract

In recent years, accumulating evidence has supported the hypothesis that lower vitamin D status is associated with several known risk factors of stroke. However, the relationship between vitamin D and stroke is still uncertain. To explore if there was an association between vitamin D status and the risk of stroke, a systematic review and a meta-analysis were conducted by searching three databases: Pubmed, Embase, and the Cochrane Library. Following the application of inclusion and exclusion criteria, the relative risk estimates of all the included studies were pooled together to compare the risk of stroke between the lowest and the highest category of vitamin D. The Newcastle-Ottawa Scale (NOS) and the Cochrane Risk of Bias Tool were used to assess the risk of bias, and the publication bias was detected by using a funnel plot and Egger's test. Nineteen studies were included and the pooled relative risk was 1.62 (95% CI: 1.34-1.96). Further analysis found that vitamin D status was associated with ischemic stroke (relative risk = 2.45, 95% CI: 1.56-3.86), but not with hemorrhagic stroke (relative risk = 2.50, 95% CI: 0.87-7.15). In conclusion, our meta-analysis supported the hypothesis that lower vitamin D status was associated with an increased risk of ischemic stroke. Further studies are required to confirm this association and to explore the association among different subtypes.

Keywords: meta-analysis; stroke; systematic review; vitamin D.

Figure 1

This is the flow chart of the selection of studies eligible for our meta-analysis. A total of 2319 records were retrieved from three databases: Pubmed, Embase, and the Cochrane library. After a strict selection process based on the inclusion and exclusion criteria, 19 studies were eligible for the meta-analysis.

Figure 2

This is the forest plot for the pooled analysis of all 19 included studies. The overall analysis was executed by Review Manager 5.3, using the random-effect model.

Figure 3

Funnel plot for all of the included studies. As shown, the dots, which represented each individual study, are distributed asymmetrically, indicating the possible existence of publication bias.