Protein in Urine Signals Decline in Memory
Two new studies have found that a type of protein called albumin in the urine strongly signals a decline in memory and cognitive impairment. Of special significance in these studies is that the levels of protein associated with the decline in memory are very low and previously have not been considered clinically significant.
Screening for protein in urine may be warranted
The presence of protein in urine (albuminuria) along with low kidney function are known characteristics of kidney disease and are associated with the risk of memory problems. Low urinary levels of albumin have not appeared to be especially significant, until now, as the results of two studies presented at the American Society of Nephrology meeting illustrate.
In one study, more than 1,200 women older than 70 who participated in the Nurses’ Health Study were followed-up every two years over six years and tested on various cognitive and memory factors. The researchers discovered that the women who had a urinary albumin-to-creatinine ratio of greater than 5 mcg/mg at the start of the study declined 2 to 7 times faster in all the memory and cognitive tests when compared with declines associated with aging alone.
According to Julie Lin, MD, of Brigham and Women’s Hospital, who headed the study, “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.” This finding supports the idea that albumin in the urine is an early indicator of diffuse vascular disease.
Dr. Lin pointed out that given the fact that aging is associated with cognitive decline and cardiovascular diseases, their findings suggest that “simple, non-invasive screening for albumin in the urine as an independent predictor for subsequent cognitive decline may represent an important public health issue.”
In the second study, researchers at Stanford University evaluated clinical data from 19,399 participants in the Renal Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. A total of 1,184 (6.1%) individuals developed cognitive impairment over an average of 3.8 years. Those who had albuminuria were 1.31 to 1.57 times more likely to have cognitive problems compared with individuals without albuminuria, and people most at risk were those who had normal kidney function.
The investigators also noted that low kidney function was associated with a greater risk for developing cognitive difficulties only among people without albuminuria. A surprising finding was that individuals with albuminuria and normal kidney function had the greatest probability for developing cognitive impairment when compared with people without albuminuria who had moderate problems with kidney function.
The bottom line in both studies appears to be that even small amounts of protein in urine may be a warning that memory and other cognitive problems will develop in the future. This information is important because, as noted by Manjula Kurella Tamura, MD, who headed the Stanford study, “albuminuria is easily measured and potentially modifiable,” and clinicians can gather this information to help them identify individuals at high risk for cognitive and memory problems in the future.
American Society of Nephrology