November 25, 2010
Protein In Urine A Warning Sign For Cognitive Decline
(Ivanhoe Newswire) -- Studies show that even small amounts of urinary protein may predict rapid cognitive decline in elderly women. Researchers recommend a simple urine test to all elderly people to identify people at risk.
A new study shows that low amounts of albumin in urine, at levels not normally considered clinically significant, strongly predict faster cognitive decline in older women. The study involved more than 1,200 women at least 70 years of age in the Nurses' Health Study who were phones every two years for three cycles and tested for general cognition, verbal/word memory, verbal fluency, and short-term memory. Julie Lin, MD (Brigham and Women's Hospital) and her colleagues found that participants with a urinary albumin-to-creatinine ratio of >5 mcg/mg at the start of the study experienced cognitive decline at a rate 2 to 7 times faster in all cognitive measures than that attributed to aging alone over an average 6 years of follow-up. "The strongest association was seen with a decline in the verbal fluency score, which has been attributed to progressive small vessel disease in the brain, which supports the view that albuminuria is an early marker of diffuse vascular disease," Dr. Lin was quoted as saying.
"Therefore, in light of the aging U.S. population, which is at risk for cognitive decline and vascular disease, simple, non-invasive screening for albumin in the urine as an independent predictor for subsequent cognitive decline may represent an important public health issue."
Two characteristics of kidney disease are excreting protein in the urine (albuminuria) and low kidney function, and both increase individuals' risk of becoming confused and forgetful. To see whether these two characteristics are related or independent in their effects on cognitive decline, Manjula Kurella Tamura, MD (Stanford University) and her colleagues studied clinical data from 19,399 individuals participating in the Renal Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. A total of 1,184 participants (6.1%) developed cognitive impairment over an average follow-up of 3.8 years. Individuals with albuminuria were 1.31-1.57 times more likely to develop cognitive impairment compared to individuals without albuminuria.
This association was strongest for individuals with normal kidney function (eGFR =60 ml/min/1.73m2) and attenuated among individuals with low levels of kidney function. Conversely, low kidney function (eGFR <60 ml/min/1.73m2) was associated with a higher risk for developing cognitive impairment only among individuals without albuminuria. Surprisingly, individuals with albuminuria and normal kidney function had a higher probability for developing cognitive impairment as compared to individuals with moderate reductions in kidney function (eGFR 45-59 ml/min/1.73m2) in the absence of albuminuria. The findings indicate that the presence of protein in the urine, even in small amounts, could be a warning sign that a patient may later have difficulty thinking clearly.
"The results are important because albuminuria is easily measured and potentially modifiable. Incorporating information about albuminuria along with kidney function should help clinicians identify patients at high risk for subsequent cognitive decline and dementia," Dr. Kurella Tamura was quoted as saying.
SOURCE: American Society of Nephrology's 43rd Annual Meeting and Scientific Exposition held in Denver, CO from November 16-21, 2010