Study Title:

Vitamin B12 and the Risk of Alzheimer Disease

Study Abstract

Objective: To examine the relation between serum levels of homocysteine (tHcy) and holotranscobalamin (holoTC), the active fraction of vitamin B12, and risk of incident Alzheimer disease (AD) in a sample of Finnish community-dwelling elderly.

Methods: A dementia-free sample of 271 subjects aged 65–79 years derived from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study was followed up for 7 years to detect incident AD. The association between serum tHcy and holoTC with AD was analyzed with multiple logistic regression after adjusting for several potential confounders, including common vascular risk factors.

Results: The odds ratios (ORs) (95% confidence interval [CI]) for AD were 1.16 (1.04–1.31) per increase of 1 µmol/L of tHcy at baseline and 0.980 (0.965–0.995) for each increase of 1 pmol/L baseline holoTC. Adjustment for several potential confounders including age, sex, education, APOE 4 allele, body mass index, Mini-Mental State Examination, smoking, stroke, and blood pressure did not alter the associations: ORs (95% CI) for AD became 1.19 (1.01–1.39) for tHcy and 0.977 (0.958–0.997) for holoTC. Adjusting for holoTC attenuated the tHcy–AD link (OR changed from 1.16 to 1.10, 95% CI 0.96–1.25). The holoTC–AD relationship was less influenced by controlling for tHcy (OR changed from 0.980 to 0.984, 95% CI 0.968–1.000). Addition of folate did not change any of the results.

Conclusions: This study suggests that both tHcy and holoTC may be involved in the development of AD. The tHcy–AD link may be partly explained by serum holoTC. The role of holoTC in AD should be further investigated.

From press release:

A new study shows that vitamin B12 may protect against Alzheimer's disease, adding more evidence to the scientific debate about whether the vitamin is effective in reducing the risk of memory loss.

The research will be published in the October 19, 2010, issue of Neurology®, the medical journal of the American Academy of Neurology.

"Our findings show the need for further research on the role of vitamin B12 as a marker for identifying people who are at increased risk of Alzheimer's disease," said study author Babak Hooshmand, MD, MSc, with Karolinska Institutet in Stockholm, Sweden. "Low levels of vitamin B12 are surprisingly common in the elderly. However, the few studies that have investigated the usefulness of vitamin B12 supplements to reduce the risk of memory loss have had mixed results."

For the seven-year study, researchers took blood samples from 271 Finnish people age 65 to 79 who did not have dementia at the start of the study. During that time, 17 people developed Alzheimer's disease. Blood samples were tested for levels for homocysteine, an amino acid associated with vitamin B12, and for levels of the active portion of the vitamin, called holotranscobalamin. Too much homocysteine in the blood has been linked to negative effects on the brain, such as stroke. However, higher levels of vitamin B12 can lower homocysteine.

The study found that for each micromolar increase in the concentration of homocysteine, the risk of Alzheimer's disease increased by 16 percent, whereas each picomolar increase in concentration of the active form of vitamin B12 reduced risk by two percent. The results stayed the same after taking into account other factors, such as age, gender, education, smoking status, blood pressure and body mass index. The addition of folate did not appear to raise or lower the risk of Alzheimer's disease.

"More research is needed to confirm these findings before vitamin B12 should be used solely as a supplement to help protect memory," said Hooshmand.

Vitamin B12 can be found in fish, poultry and other meat products.

Study Information

B. Hooshmand, A. Solomon, I. Kåreholt, J. Leiviskä, M. Rusanen, S. Ahtiluoto, B. Winblad, T. Laatikainen, H. Soininen, and M. Kivipelto
Homocysteine and holotranscobalamin and the risk of Alzheimer disease: A longitudinal study
2010 October
Karolinska Institutet in Stockholm, Sweden

Full Study