Homocysteine is a sulfur-containing amino acid found in the blood. Deficiencies in the B vitamins folic acid (folate) and B-12 are often associated with elevated homocysteine levels. Blood homocysteine elevations have previously been linked to an increased risk for cognitive impairment later in life. This link, however, has not been conclusively confirmed. To investigate this association, researchers evaluated homocysteine levels compared to the occurence of dementia or cognitive impairment without dementia (CIND) in an ongoing cohort study of 1,779 Mexican Americans aged 60-101. Analysis of this data confirmed that higher homocysteine concentrations are associated with an increased incidence of both dementia and CIND.
Because increased folic acid and B-12 consumption is associated with lower homocysteine levels, blood levels of these vitamins were also analyzed. Compared to median plasma B-12 levels, those with the lowest levels had a 61% increased risk for cognitive impairment, while those with the highest B-12 levels had a 6% reduction in risk. No reduction in risk was observed for folic acid levels, presumably due to a general lack of folic acid deficiency in this population. The authors conclude that increased consumption of B-12 may reduce the risk for both dementia and CIND in older adults.
Haan, MN; Miller JW et al. Homocysteine, B vitamins and the incidence of dementia and cognitive impairment: results from the Sacramento Area Latino Study on Aging. Am J Clin Nutr., 2007;85:511-7.