Nutrition status affects cognitive impairment in the elderly

Old age is often associated with cognitive impairment that can range in severity from mild memory loss to severely debilitating conditions such as Alzheimer disease. By current estimates, more than one million of the elderly in Europe and about 750,000 elderly in the United States and Canada become cognitively impaired each year, and often require expensive long-term care. Though it was previously thought that such age-related decline was inevitable, recent research suggests that deficiencies of folate or vitamin B-12 and elevations of plasma homocysteine (tHcy) are associated with cognitive impairment and dementia. Publishing in the American Journal of Clinical Nutrition, Duthie et al. investigated the associations between cognitive impairment and plasma concentrations of folate, vitamin B-12, and tHcy in 331 older subjects. They found significant negative effects on cognition in the elderly subjects who had deficiencies of folic acid or vitamin B-12 and elevated tHcy.

The men and women participants were survivors of the Scottish Mental Surveys of 1932 and 1947, which conducted intelligence tests in Scottish School Children. From 1997-1999, participants in the two groups–born in 1921 and now aged 76-78, and born in 1936 and now aged 61-63–took part in the study. Cognitive status was measured by standardized tests that assessed nonverbal intelligence, speed of information processing, pattern recognition, and general cognitive ability, and plasma concentrations of tHcy, folate, and vitamin B-12 were determined.

The older group (born in 1921) had increased levels of tHcy, which correlated both with lower serum folate and vitamin B-12 concentrations and with lower cognitive test scores. Those who had higher plasma concentrations of folate and B-12 scored higher on 4 of the 6 cognition tests.1 Among the group born in 1936, higher folate concentrations correlated with higher scores on one of the assessment tests, but otherwise no effects of B vitamins or tHcy were apparent.

These findings have important implications for the design of preventative nutritional strategies aimed at delaying cognitive decline in the elderly. In an accompanying editorial, Smith discusses findings in previous studies that both vascular dementia and Alzheimer disease are associated with high levels of tHcy, which may have a neurotoxic effect. He suggests that clinical trials should be developed with the aim of lowering tHcy in the elderly by administration of folic acid or vitamin B-12, which may lower tHcy and prevent those with mild cognitive impairment from developing Alzheimer disease.

Duthie, Susan J et al. Homocysteine, B vitamin status, and cognitive function in the elderly. Am J Clin Nutr 2002;75:908-13.

Smith, A David. Homocysteine, B vitamins and cognitive deficit in the elderly. Am J Clin Nutr 2002;75:785-6.

This media release is provided by The American Society for Clinical Nutrition to provide current information on nutrition-related research. This information should not be construed as medical advice. If you have a medical concern, consult your doctor. To see the complete text of this article, please go to:

http://www.faseb.org/ajcn/May/13256-Duthie.pdf

or

http://www.faseb.org/ajcn/May/13649-Smith.pdf

For more information, please contact: sd@rri.sari.ac.uk or david.smith@pharm.ox.ac.uk

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