Vitamin D, cognition, and dementia: a systematic review and meta-analysis

Neurology. 2012 Sep 25;79(13):1397-405. doi: 10.1212/WNL.0b013e31826c197f.

Abstract

Objective: To examine the association between cognitive function and dementia with vitamin D concentration in adults.

Methods: Five databases were searched for English-language studies up to August 2010, and included all study designs with a comparative group. Cognitive function or impairment was defined by tests of global or domain-specific cognitive performance and dementia was diagnosed according to recognized criteria. A vitamin D measurement was required. Two authors independently extracted data and assessed study quality using predefined criteria. The Q statistic and I² methods were used to test for heterogeneity. We conducted meta-analyses using random effects models for the weighted mean difference (WMD) and Hedge's g.

Results: Thirty-seven studies were included; 8 contained data allowing mean Mini-Mental State Examination (MMSE) scores to be compared between participants with vitamin D <50 nmol/L to those with values ≥50 nmol/L. There was significant heterogeneity among the studies that compared the WMD for MMSE but an overall positive effect for the higher vitamin D group (1.2, 95% confidence interval [CI] 0.5 to 1.9; I² = 0.65; p = 0.002). The small positive effect persisted despite several sensitivity analyses. Six studies presented data comparing Alzheimer disease (AD) to controls but 2 utilized a method withdrawn from commercial use. For the remaining 4 studies the AD group had a lower vitamin D concentration compared to the control group (WMD = -6.2 nmol/L, 95% CI -10.6 to -1.8) with no heterogeneity (I² < 0.01; p = 0.53).

Conclusion: These results suggest that lower vitamin D concentrations are associated with poorer cognitive function and a higher risk of AD. Further studies are required to determine the significance and potential public health benefit of this association.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Cognition / physiology*
  • Cognition Disorders / diagnosis
  • Cognition Disorders / metabolism
  • Cognition Disorders / physiopathology*
  • Dementia / diagnosis
  • Dementia / metabolism
  • Dementia / physiopathology*
  • Humans
  • Randomized Controlled Trials as Topic / methods
  • Randomized Controlled Trials as Topic / trends
  • Vitamin D / pharmacology*

Substances

  • Vitamin D