The Correlation Between Vitamin D Deficiency And Dementia And Alzheimer’s Disease: A Meta-analysis

Objective: To explore the relationship between serum vitamin D(VD)deficiency and the risk of dementia and Alzheimer disease(AD),and to further explore different levels of serum25-(OH)D lack of relationship with the risk of dementia and AD through the systematic review.Methods: The searched content is the relevant literature of the relationship between the risk of dementia or AD and VD or 25-(OH)D deficiency.We formulated a search strategy according to the Cochrane manual,systematically searched the four databases of the Pubmed,the Cochrane Library,the Embase and CNKI,and manually searched the reference lists in the relevant literatures.The search time limit is from database construction to March 2020.We imported all the retrieved literatures into the literature manager of Endnote,removed duplicate literatures,and then gradually removed the literatures that did not meet the inclusion criteria by reading the titles,abstracts and full texts,and finally extracted the relevant information according to the Cochrane manual standardization.The main outcomes are: serum 25-(OH)D deficiency(<20 ng / ml)and HRs(HRs,hazard ratios)and corresponding 95% CI of dementia or AD;the moderate serum 25-(OH)D deficiency(10-20 ng/ml)or severe serum 25-(OH)D deficiency(<10 ng/ml)and HRs and corresponding 95% CI of dementia or AD,respectively.The secondary outcomes include: consideration of the association of Apolipoprotein E(APOE)gene with dementia and AD compared with literatures without consideration of APOE gene;the association of cohort studies compared to cross-sectional studies with dementia;the correlation between the risk of dementia and AD and follow-up time.In addition,we also measured the sensitivity of the study and publication bias.All statistical analysis was performed using Stata 12.0 software.Setting P <0.05 has statistical significance.Results: A total of 12 studies were included,including 8 cohort studies and 4cross-sectional studies.The total HRs of VD deficiency and the risk of dementia and AD were1.32(95% CI: 1.16,1.52)and 1.34(95% CI: 1.13,1.60),respectively.The total HRs of moderate VD deficiency and the risk of dementia and AD were 1.48(95% CI: 1.19,1.85)and1.51(95% CI: 1.04,2.18),and severe deficiency were 1.20(95% CI: 0.99,1.44)and 1.36(95% CI: 1.01,1.84),respectively.In the subgroup analyses,the association between vitaminD deficiency and dementia was observed in the subgroup of studies that considered the serum25(OH)D APOE gene compared to studies that did not consider the APOE gene(pooled HRs:1.47,95% CI: 1.10,1.98 vs.1.28,95% CI: 1.10,1.49).Similarly,the association between vitamin D deficiency and AD was observed in the subgroup of studies that considered the serum 25(OH)D APOE gene compared to studies that did not consider the APOE gene:(pooled HRs: 1.34,95% CI: 1.13,1.60 vs.1.27,95% CI: 1.05,1.54).The P values ??of the correlation between dementia and AD risk and follow-up time were 0.03 and 0.02,respectively.The significant association was observed in cohort studies compared to cross-sectional studies(pooled HRs: 1.30,95% CI: 1.13,1.50 vs.1.32,95% CI: 1.16,1.52)(P<0.05).Conclusion: This study found significant positive associations between VD deficiency and risk of dementia and AD.Subgroup analysis indicated that VD moderate deficiency(< 10ng/ml)was more strongly associated with the risk of dementia and AD compared with severe deficiency(10–20 ng/ml),indicating that the risk of dementia and AD was reduced with increased VD.The subgroup considering the APOE gene was more significantly associated with the risk of dementia and AD compared to the literatures without considering the APOE gene;the risk of dementia and AD was not significantly associated with the type of studies.In addition,there was a certain correlation between the risk of dementia and AD and the follow-up time,that is,the longer the follow-up time,the higher the risk of dementia and AD.