Impaired kidney function is associated with lower cognitive function in the elder general population. Results from the Good Aging in Skåne (GÅS) cohort study.

BACKGROUND

A possible connection on vascular basis between impaired kidney function and cognitive dysfunction has been suggested in previous studies. Contradictory results regarding specific cognitive domains have been reported. The aim for this study was to investigate the association between kidney function and specific cognitive domains.

METHODS

In this cross-sectional design, data from the general population based cohort study "Good aging in Skåne" (GÅS) was used. The sample included 2931 subjects ages 60 to 93 randomly selected from the southern part of Sweden. Estimated glomerular filtration rate (eGFR) for both creatinine and cystatine C was calculated using the chronic kidney disease epidemiology collaboration (CKD-EPI) equation. The subjects underwent a test battery of neuropsychological tests assessing global cognitive function, learning and memory, language, complex attention, executive function, perceptual motor and meta-memory. Adjustments were made for age, sex, education and country of origin.

RESULTS

After adjustment for demographic variables, impaired kidney function was associated with 0.41 points worse result in MMSE, 0.56 points worse result in recognition, 0.66 points worse result in word fluency, 0.45 points worse result in digit cancellation, 0.99 points worse result in pattern comparison, and 3.71 s longer time to finish TMT B-A. Associations to cognitive function was also noted for mildly impaired kidney function defined as eGFR 45- < 60 ml/min/1,73m. No association was found between kidney function and meta-memory.

CONCLUSIONS

Impaired kidney function as well as the severity of impaired kidney function is associated with impairment in learning and memory, language, complex attention, executive function and global cognitive function, but not meta-memory.