Even mildly elevated levels of uric acid in the elderly are associated with slower thinking and memory problems, according to a report by researchers at Yale and Johns Hopkins Schools of Medicine in Neuropsychology.
The researchers found that elderly individuals with uric acid levels at the high end of the normal range had the lowest scores on tests measuring mental processing speed, verbal memory and working memory. The study included among 96 persons between the ages of 60 and 92.
“These findings suggest that high normal concentrations of serum uric acid should be added to the growing list of cardiovascular and metabolic biomarkers of mild cognitive impairment among elderly adults,” said Godfrey Pearlson, M.D., psychiatry professor at Yale and co-author of the study.
Uric acid is produced from digested food and the breakdown of the body's cells. Most uric acid is filtered out by the kidneys and passes out of the body in urine. The level of uric acid in the blood increases if too much is being produced or if the kidneys are not able to remove it from the blood normally.
The researchers said the mechanism linking uric acid levels and cognitive functioning is unknown. Elevated uric acid commonly accompanies hypertension, increased concentration of lipids in the bloodstream, obesity, renal disease, insulin resistance, and the metabolic syndrome. The investigators found that the relationship of uric acid to cognition survived correction for most of these factors.
One question raised in the study was how the findings could be reconciled with evidence that uric acid is an antioxidant that might protect against the development of Alzheimer’s and Parkinson’s disease.
“One possibility,” said Pearlson, “is that despite being an antioxidant, uric acid can acquire pro-oxidant properties that damage the vascular endothelium in certain conditions and might even play a key role in the development of accelerated atherosclerosis.”
The National Institutes of Health, the Therapeutic Cognitive Neuroscience Fund, and the Benjamin and Adith Miller Family Endowment on Aging, Alzheimer’s and Autism Research provided funding for the research.
Neuropsychology 21: 136-140 (January 2007)
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