Journal
NEUROLOGY
Volume 79, Issue 13, Pages 1397-1405Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1212/WNL.0b013e31826c197f
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Funding
- Canadian Institutes of Health Research
- Agency for Healthcare Research and Quality
- Canada Foundation for Innovation (CFI)
- Ontario Ministry of Health and Long-Term Care
- Novartis
- Janssen-Ortho
- Schlegel Research Chair in Geriatric Medicine at the University of Waterloo
- Heart and Stroke Foundation of Ontario
- Nutrition Society
- American Society of Nutrition
- James Tudor Foundation
- Sir Halley Stewart Trust
- Norman Family Charitable Trust
- Peninsula Medical School Foundation
- Age Related Diseases and Health Trust
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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 I-2 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; I-2 = 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 Six studies presented data comparing Alzheimer disease (AD) to controls but 2 utilized a method withdrawn from commercial use.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 (I-2 < 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. Neurology (R) 2012;79:1397-1405
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