High Prevalence of Cognitive Impairment Seen in CKD Patients

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Neurology

High Prevalence of Cognitive Impairment Seen in CKD Patients

By: DOUG BRUNK, Internal Medicine News Digital Network

05/10/11
FROM THE ANNUAL MEETING OF THE AMERICAN ACADEMY OF NEUROLOGY

VITALS
Major Finding: The prevalence of moderate cognitive impairment was 46% among patients with moderate chronic kidney disease, 36% among patients receiving hemodialysis, and 27% among controls.

Data Source: An ongoing prospective study of 81 patients with moderate chronic kidney disease, 338 patients receiving hemodialysis, and 101 controls.

Disclosures: The study was funded by the Minneapolis Medical Research Foundation, Satellite Healthcare, and the National Institute on Aging. Dr. Murray said she had no relevant financial disclosures.

HONOLULU – Patients with moderate chronic kidney disease had a higher prevalence of moderate cognitive impairment than did patients receiving hemodialysis in a prospective pilot study conducted at two clinics.

"Clinicians think about the apo E4 gene, advanced age, education level, and history of stroke as being risk factors for cognitive impairment, but they don’t think about chronic kidney disease as a risk factor," lead investigator Dr. Anne M. Murray said in an interview during a poster session at the annual meeting of the American Academy of Neurology. "It’s a strong risk factor."

Dr. Anne M. Murray

Findings from recent studies suggest that there is an association between estimated glomerular filtration rate (GFR) and cognitive function, said Dr. Murray, a geriatrician and neuroepidemiologist with the Hennepin County Medical Center, Minneapolis, but the severity of cognitive impairment and extent that specific cognitive domains are affected remain unknown.

She and her associates at two Minneapolis clinics compared the frequency of mild, moderate, and severe cognitive impairment in 81 patients with an estimated GFR of less than 50 mL/min per 1.73 m2 (stage 3B to stage 5 chronic kidney disease) against 338 hemodialysis patients and 101 controls. The patients with chronic kidney disease had a mean estimated GFR of 31 mL/min per 1.73 m2.

In the study, the researchers administered a 45-minute battery of nine validated neuropsychological tests to patients with chronic kidney disease and to controls, while hemodialysis patients were tested before dialysis, 1 hour after, or on the day after dialysis. They used the Modified Mini-Mental State Examination (maximum score, 100) to measure global cognitive function, and other tests to measure performance in the domains of memory, executive function, and language.

More than half of patients in the chronic kidney disease group (59%) were African American, compared with 11% in the hemodialysis group and 8% in the control group.

The mean ages of patients in the chronic kidney disease group, hemodialysis group, and control group were 60 years, 71 years, and 69 years, respectively. The prevalence of mild cognitive impairment was 7%, 14%, and 14%; the prevalence of moderate cognitive impairment was 46%, 36%, and 27%; the prevalence of severe cognitive impairment was 31%, 37%, and 13%; and the prevalence of normal cognitive function was 16%, 13%, and 47%.

Dr. Murray reported that the mean Modified Mini-Mental State Examination score was 92.0 in the chronic kidney disease group (consistent with early mild cognitive impairment), 88.3 in the hemodialysis group (consistent with early dementia), and 94.3 in the control group (consistent with normal cognitive function).

Black race was strongly associated with severe cognitive impairment among patients with chronic kidney disease (P less than .015), but no other significant bivariate associations were observed between cognitive status and demographic factors, estimated GFR, or history of stroke, in part because of the study’s small sample size, she said.

"If one of your patients has moderate chronic kidney disease – an estimated GFR of less than 50 mL/min per 1.73 m2 – they should be screened for cognitive impairment, because they probably can’t take their medications on their own, and their judgment is probably impaired when it comes to making a decision about starting dialysis," Dr. Murray noted.

The limitations of the study include its small number of patients, no matching of cohorts for age or race, and a lack of brain imaging to detect cerebrovascular disease. The study is ongoing and will be expanded to include 300 patients, she said.

The study was funded by the Minneapolis Medical Research Foundation, Satellite Healthcare, and the National Institute on Aging. Dr. Murray said she had no relevant financial disclosures.

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