ABSTRACT
BACKGROUND: The emerging role of vitamin D has drawn the attention of researchers around the world, including its involvement in cardiovascular complications among individuals with diabetes. AIM: This study aimed to obtain comprehensive evidence on the association between serum vitamin D level and the risk of cardiovascular disease among patients with diabetes. METHODS: Systematic search was performed on July 1st, 2023, to identify and screen published literature reporting the association between vitamin D and cardiovascular disease among diabetic patients in six databases. Each eligible study was appraised for its quality using modified Newcastle Ottawa Scale for cross-sectional and cohort studies. Meta-analysis was performed using Dersimonian-Laird random effect model or fix-effect model. The heterogeneity and publication bias were judged based on percentage of I2 and the symmetry of Begg's funnel plot, respectively. RESULTS: As many as 22 studies were found eligible for the systematic review. A meta-analysis from 13 studies comprising of 3850 and 1797 (control and exposure groups, respectively) revealed that serum vitamin D level was significantly lower in patients with diabetes and cardiovascular diseases (Z = 4.89; p-total<0.001; SMD = 0.68 [95%CI: 0.41-0.95]), yet the heterogeneity was high. Following the adjustment of removing the potential outliers, the same results were still observed (Z = 6.19; p-total<0.001; SMD = 0.35 [95%CI: 0.24-0.46]). Though decreased, high heterogeneity could not be resolved, resulting in moderate level of this evidence. Another pooled analysis of 7 studies with 4211 patients in control group and 2381 patients in exposure group revealed that lower level of serum vitamin D is a risk factor for cardiovascular disease incidence among diabetic patients (Z = 4.89; p-total<0.001; OR: 1.76 [95%CI: 1.4-2.2]). CONCLUSION: Serum vitamin D level status is a risk factor for developing cardiovascular diseases among diabetic patients, hence should be carefully monitored and maintained. PROSPERO REGISTRATION: CRD42023437698.