Vitamin D, cognition, and dementia: a systematic review and meta-analysis. - GreenMedInfo Summary
Vitamin D, cognition, and dementia: a systematic review and meta-analysis.
Neurology. 2012 Sep 25 ;79(13):1397-405. PMID: 23008220
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada. firstname.lastname@example.org
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 Six studies presented data comparing Alzheimer disease (AD) to controls but 2 utilized a method withdrawn from commercial use.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.