Vitamin D concentration and risk of Alzheimer disease: A meta-analysis of prospective cohort studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of non-randomized prospective cohort studies
PubMed 31464906 · doi:10.1097/MD.0000000000016804
What was done
Authors searched PubMed, Embase, and Cochrane Library databases to conduct a meta-analysis of prospective cohort studies assessing the relationship between serum vitamin D concentrations and incident Alzheimer disease (AD) in adults. Random-effects models pooled adjusted relative risks (RRs) from 6 prospective cohort studies comprising 21,692 individuals and 1,607 incident AD cases.
What was found
Random-effects pooling across 4 cohort studies evaluating serum vitamin D concentrations <25 nmol/L and 25 to 50 nmol/L showed no statistically significant increased risk of AD after adjustment for established risk factors. Pooling 3 cohort studies analyzing risk per standard deviation decrease in serum vitamin D similarly showed no significant association with AD. Exact numerical risk estimates, confidence intervals, and p-values were omitted from the abstract.
Why it matters
This review suggests that low circulating vitamin D status may not be an independent risk factor for developing Alzheimer disease once standard confounders are controlled.
Limits
The abstract reports no numerical point estimates, confidence intervals, or heterogeneity metrics. Synthesizing observational cohort studies cannot confirm causality and remains susceptible to residual confounding and reverse causation. Subgroup analyses relied on small subsets of only 3 to 4 studies.
Cited by
- contradicts Vitamin D deficiency is a significant risk factor for Alzheimer's disease and accelerates disease progression in people who already have Alzheimer's.