A new study published in the medical journal Neurology suggests that impaired kidney function is a risk factor for cognitive decline in old age.
The study, conducted by researchers at Rush University Medical Center, found that poor kidney function was linked specifically with cognition related to memory functions. Damage to one of these functions, episodic memory, which retrieves memories of time, place, associated emotions and other contextual knowledge, is often the earliest sign of Alzheimer's disease.
"Given the dearth of modifiable risk factors for age-related cognitive decline, these results have important public health implications," said Dr. Aron Buchman, a neuroscientist in the Rush Alzheimer's Disease Center. "Further work to understand the link between kidney function and the brain may provide new strategies for preventing memory loss in elders."
Buchman said the findings suggest that there are common disease processes that affect both the brain and the kidneys in the elderly, and hypothesized that underlying vascular problems, such as diabetes and hypertension, may account for the association between kidney problems and cognitive decline.
The study analyzed data for 886 older adults who participated in the Rush Memory and Aging Project, a group of community-dwelling seniors with a mean age of 81, all of them initially free of dementia. The participants were examined annually for up to six years to track changes in cognition over time. Cognitive assessments included multiple tests that were summarized as a composite measure of overall cognition and of five individual cognitive abilities.
The individual cognitive systems assessed were visuospatial ability; perceptual speed, or the ability to quickly and accurately compare letters, numbers, objects, pictures or patterns; semantic memory, related to meaning, understanding and other concept-based knowledge; working memory, which temporarily stores and manipulates information; and episodic memory.
Ruling out the influence of factors like aging and medications, which can affect cognition, the researchers found that poor kidney function, assessed at the beginning of the study, was linked with a more rapid rate of decline in cognition over the next several years - not in visuospatial ability or perceptual speed, but in three specific areas: episodic, semantic and working memory.
The rate of decline in cognition was equivalent to that of a person seven years older at baseline, Buchman said.
The study was supported by funds from the National Institute on Aging, the Illinois Department of Public Health and the Robert C. Borwell Endowment Fund.
About Rush: Rush University Medical Center includes a 674-bed (staffed) hospital; the Johnston R. Bowman Health Center; and Rush University (Rush Medical College, College of Nursing, College of Health Sciences and the Graduate College).
Rush is currently constructing a 14-floor, 806,000-square-foot hospital building at the corner of Ashland Avenue and Congress Parkway. The new hospital, scheduled to open in 2012, is the centerpiece of a $1-billion, 10-year campus redevelopment plan called the Rush Transformation, which also includes a new orthopedics building (to open in Fall 2009), a new parking garage and central power plant completed in June 2009, renovations of selected existing buildings and demolition of obsolete buildings. The new hospital is being designed and built to conserve energy and water, reduce waste and use sustainable building materials. Rush is seeking Leadership in Energy and Environmental Design (LEED) gold certification from the U.S. Green Building Council. It will be the first full-service "green" hospital in Chicago.
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