Vitamin D Supplement for Prevention of Alzheimer's Disease: A Systematic Review and Meta-Analysis
Ya-Ge Du, Fangfang Liang, Liping Zhang, Jie Liu, Haoying Dou
Abstract
BACKGROUND: Prevention of Alzheimer's disease (AD) with Vitamin D (VD) supplementation has been studied widely, but the results in the literature are very conflicting. THE STUDY QUESTION: Can VD supplementation really prevent AD? STUDY DESIGN: The literature was searched from PubMed, Cochrane library, Web of Science, and EMBASE to identify relevant randomized clinical trials (RCTs). The titles and abstracts were evaluated independently by 2 of the authors. RESULTS: Nine RCTs with 2345 participants were included. In the meta-analysis, we found no significant difference in the Mini-Mental State Examination, verbal fluency, verbal memory, visual ability, and attention scores between the VD intervention group and comparison group [standardized mean difference (SMD) = -0.05, 95% confidence interval (CI) = -0.51 to 0.41; SMD = -0.01, 95% CI = -0.13 to 0.11; SMD = 0.12, 95% CI = -0.45 to 0.69; SMD = 0.42, 95% CI = -0.15 to 1.00; and SMD = 0.01, 95% CI = -0.24 to 0.27, respectively]. In subgroup analysis, we found that the intervention with only VD or plus calcium, follow-up duration, and baseline 25(OH)D levels did not explain the cause for high heterogeneity. CONCLUSIONS: Overall, the current evidence did not support the beneficial effect of VD supplement to prevent AD. High quality RCTs and further studies are needed to clarify the effects of VD supplementation on preventing AD.