Urinary Protein Excretion Increases Risk of Cognitive Decline

Albuminuria, a pathological condition where the protein albumin is excreted in the urine, and low kidney function as estimated by the glomerular filtration rate, are indicative of cognitive impairment.

In a study, carried out at Stanford University (Stanford, CA, USA), clinical data from 19,399 individuals was collected to see whether cognitive decline was associated with albuminuria and deficient renal function. 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 who had an estimated glomerular filtration rate (eGFR) equal to or greater than 60 mL/min/1.73 m², but was attenuated among individuals with low levels of kidney function. Conversely, low kidney function with eGFR of less than 60 mL/min/1.73 m², was associated with a higher risk for developing cognitive impairment only among individuals without albuminuria. 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 with eGFR of 45-59 mL/min/1.73 m², in the absence of albuminuria.

Manjula Kurella Tamura, MD, from Stanford University, said, "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." 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 study was presented orally at the annual meeting of American Society of Nephrology, held in Denver, CO, USA, November 16 – 21, 2010.

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