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| |  Elevated Homocysteine Levels May Be Possible Risk Factor For Alzheimer Disease DURHAM, NC -- Oct. 20, 1998 -- Alzheimer disease (AD) may be associated with moderately elevated blood levels of the amino acid homocysteine, according to an article appearing in the November issue of the journal Archives of Neurology. Robert Clarke, M.D., and A. David Smith, D.Phil., from University of Oxford, England, and colleagues studied 164 patients aged 55 years or older with a clinical diagnosis of dementia of Alzheimer type (DAT), 76 of whom had histologically confirmed AD, to examine the association of AD with blood levels of total homocysteine (tHcy) and its biological determinants folate and vitamin B12. An elevated blood plasma level of tHcy is a known risk factor for vascular disease, including heart disease and stroke. Smith discussed the findings of the study at the American Medical Association's 17th annual science reporters conference on Sunday. "We observed that there were significant associations of histologically confirmed AD and of vascular dementia with moderately elevated blood levels of tHcy and with reduced blood levels of folate and vitamin B12," the researchers write. In a separate interview, Smith stressed that these biochemical changes in the blood could be a consequence rather than a cause of AD and that further work will be required to distinguish between these two interpretations. He recommends the implementation of clinical trials to see whether or not lowering homocysteine levels with folic acid and vitamin B12 influences the development of AD. "These findings are important because they provide a testable hypothesis that it may be possible to prevent Alzheimer disease from developing in a portion of potential sufferers," he said, adding that people should not take extra folic acid without consulting a physician. According to the article, moderately elevated levels of tHcy are common in the population and increase with age and have been reported in patients with clinical diagnoses of DAT or vascular dementia. Several studies have demonstrated inverse associations between clinically diagnosed DAT and folate and vitamin B12 levels. The researchers found that the 76 patients who had AD not only had elevated blood levels of tHcy but also had lower blood levels of folate and vitamin B12 than the 108 control subjects. Fifty-nine percent of histologically confirmed AD patients had a tHcy value in the top third of the control distribution. Seventy-six percent of the patients with confirmed AD had serum folate concentration in the bottom third of the control distribution. The strength of the association between vitamin B12 levels and confirmed AD was similar to that for tHcy. The authors studied the radiological evidence of disease progression three years after the patients were first seen. Patients with DAT who had tHcy levels in the middle and upper thirds of the control distribution at their first visit showed progressive brain atrophy, while the patients in the lower third showed little atrophy. The association between blood levels of folate and vitamin B12 at the beginning of the study and disease progression showed a similar trend, but the differences were not statistically significant. The authors suggest that the low vitamin levels and high tHcy levels either existed before the start of AD or developed early in the disease phase. "Our data show that elevated tHcy levels and low folate and vitamin B12 levels are common in patients with AD," they said. “The stability of tHcy levels and lack of relationship with duration of symptoms argue against these associations being a consequence of disease and warrant further studies to determine the relevance of these associations to the onset and progression of AD." Related Links: Archives of Neurology
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