Older Adults with Elevated Levels of Uric Acid
Uric acid is the end product of purine metabolism (purines are building blocks of RNA and DNA). Most uric acid produced in the body is excreted by the kidneys. An overproduction of uric acid occurs when there is excessive breakdown of cells, which contain purines, or an inability of the kidneys to excrete uric acid.
Humans produce only small quantities of uric acid. In human blood, uric acid concentrations between 3.6 mg/dL (~214µmol/L) and 8.3 mg/dL (~494µmol/L) (1mg/dL=59.48 µmol/L) are considered normal by the American Medical Association, although significantly lower levels are common in vegetarians due to a decreased intake of purine-rich meat.
Greater-than-normal levels of uric acid (hyperuricemia) may indicate:
- lead poisoning
- polycythemia vera
- renal failure
- toxemia of pregnancy
- purine-rich diet
- severe exercise
Lower-than-normal levels of uric acid may indicate:
- Fanconi's syndrome
- Wilson's disease
- low purine diet
Older adults with high-normal levels of uric acid are significantly more likely than those with low-moderate concentrations to experience mild cognitive impairment (loss of memory), according to results of a study published in the medical journal Neuropsychology.
While mild cognitive impairment can affect many areas of cognition — such as language, attention, reasoning, judgment, reading and writing — most research has focused on its effects on memory.The concept of cognition is closely related to such abstract concepts as mind, reasoning, perception, intelligence, learning, and many others that describe numerous capabilities of human mind and expected properties of artificial or synthetic intelligence. Cognition is an abstract property of advanced living organisms; therefore, it is studied as a direct property of a brain or of an abstract mind on subsymbolic and symbolic levels.
On an individual being level, these questions are studied by the separate fields above, but are also more integrated into cognitive ontology of various kinds. This challenges the older linguistically dependent views of ontology, wherein one could debate being, perceiving, and doing, with no cognizance of innate human limits, varying human lifeways, and loyalties that may let a being "know" something (see qualia) that for others remains very much in doubt.
"Among possible markers of age-related cognitive decline, uric acid is controversial," Dr. David J. Schretlen, of Johns Hopkins University Hospital, Baltimore, and colleagues note. On one hand, uric acid has antioxidant properties, which inhibits cell damage, while on the other hand, it is often elevated in diseases that frequently lead to cognitive impairment.
The researchers studied 96 community-dwelling adults between the ages of 65 and 92 years who underwent physical and neurological examinations, psychiatric interviews, laboratory blood studies, MRI brain scans, and neuropsychological testing.
Blood levels of uric acid among the women ranged from 1.5 to 7.1 mg/dL. For men, levels ranged from 1.5 to 7.6 mg/dL.
Subjects with mildly elevated (but normal) uric acid - greater than 5.8 mg/dL for men or greater than 4.8 mg/dL for women -- were significantly more likely to have a below-average performance on cognitive measures. This included having nearly 6-times the likelihood impaired processing speed; 3.5-times for working memory; and 2.7 times for verbal learning and memory.
After the researchers corrected the data for possible overestimation by adding in the potential effects of age, sex, race, years of education, and self-reported hypertension, diabetes, smoking, and history of alcohol abuse or dependence, they found that high blood levels of uric acid "remained associated with increased risk of below average performance on measures of working memory (4.25-times) and verbal learning/memory (5.02-times)," Schretlen's team reports.
They suggest these findings might justify a clinical trial of an agent that blocks xanthine oxidase, an enzyme involved in uric acid formation, to see if it improves cognitive performance in elderly people with high uric acid levels.
While mild cognitive impairment can affect many areas of cognition — such as language, attention, reasoning, judgment, reading and writing — most research has focused on its effects on memory.