Table 5. Summary of Systematic Reviews Examining the Association Between Vitamin B12 (or Hyperhomocysteinemia) and the Onset of Dementia.
| Author, Year | Question | Sources/Dates Searched | No. of Studies Included | Conclusion |
|---|---|---|---|---|
| Moore et al, 2012 (26) | What is the association between low vitamin B12 levels, neurodegenerative disease, and cognitive impairment? | MEDLINE, PsychINFO, PubMed/to 2011 | Unclear | Low serum vitamin B12 levels are associated with neurodegenerative disease and cognitive impairment. |
| Ho et al, 2011 (27) | What is the role of Hcy as a risk factor for dementia, cognitive decline, and cognitive impairment? | PubMed, Embase, PsychINFO, Biosis, Cochrane Library/to 2008 | 17 | Individuals with AD have higher Hcy levels than controls; however, a causal relationship between high Hcy level and risk of developing dementia is not supported. |
| Wald et al, 2011 (28) | What is the relationship between serum Hcy and dementia? | MEDLINE, PsychINFO/to 2009 | 8 (cohort) | There is a positive association between serum Hcy and dementia. |
| Dangour et al, 2010 (29) | What is the strength of the available evidence that serum nutrient levels, dietary consumption, or nutrient supplementation were associated with primary prevention or treatment of dementia? | PubMed, Embase, Cochrane Library/to 2007 | 33 | Available evidence is insufficient to draw definitive conclusions on the association of B vitamins with cognitive decline or dementia. |
| Van Dam and Van Gool, 2009 (30) | What is the association between Hcy levels and AD? | PubMed, Embase, PsychINFO/to 2007 | 18 | Increased serum levels of Hcy predispose to AD; more studies are needed. |
| Raman et al, 2007 (31) | What is the association between blood levels or dietary intake of B vitamins and the risk and progression of neurocognitive deficit? | MEDLINE, Commonwealth Agricultural Bureau/to 2006 | 24 (cohort) | Data supporting the association (of B vitamins and cognitive function) were limited because of the heterogeneity in cognition-assessment methodology and due to scarcity of good quality studies and standardized threshold levels for categorizing low B-vitamin status. |
| Ellinson et al, 2004 (32) | What is the evidence of an association between low serum vitamin B12 and cognitive impairment in subjects older than 60 years? | Medline, PsychINFO, CINAHL, Embase, Food and Nutrition in AGRIS, Biosis/to 2003 | 6 | The evidence does not support a correlation between serum vitamin B12 and cognitive impairment in people older than 60 years. |
Abbreviations: AD, Alzheimer disease, AGRIS, International System for Agricultural Science and Technology; CINAHL, EBSCO Cumulative Index to Nursing & Allied Health Literature; Hcy, homocysteine; No., number.