Decline in renal functioning is associated with longitudinal decline in global cognitive functioning, abstract reasoning and verbal memory.

Background: Decreased estimated glomerular filtration rate (eGFR) and higher serum creatinine (sCR) levels have been associated with longitudinal decline in global mental status measures. Longitudinal data describing change in multiple domains of cognitive functioning are needed in order to determine which specific abilities are most affected in individuals with impaired renal function.

Methods: We conducted a 5-year longitudinal study with 590 community-living individuals (mean age 62.1 years, 60.2% female, 93.2% white, 11.4% with diabetes mellitus, mean eGFR 78.4 mL/min/1.73 m²) free from dementia, acute stroke and end-stage renal disease. To measure longitudinal change-over-time, cognitive performance measures were regressed on eGFR adjusting for baseline eGFR and cognitive performance, comorbidity and vascular risk factors. Outcome measures were scores from 17 separate tests of cognitive abilities that were used to index 5 theoretically relevant domains: verbal episodic memory, visual-spatial organization and memory, scanning and tracking, working memory and similarities (abstract reasoning).

Results: Declines in eGFR values were associated with cognitive declines, when adjusted for eGFR and cognitive function scores at baseline. Change in renal functioning over time was related to change observed in global cognitive ability [b=0.21SD decline per unit ln(eGFR), 95% CI: 0.04-0.38, P=.018], verbal episodic memory [b=0.28 SD decline per unit ln(eGFR), 95% CI: 0.02-0.54, P=0.038] and abstract reasoning [b=0.36 SD decline per unit ln(eGFR), 95% CI: 0.04-0.67, P=0.025]. Decline in cognitive functioning in association with declining renal functioning was observed despite statistical adjustment for demographic variables and CVD risk factors and the exclusion of persons with dementia or a history of acute stroke.

Conclusions: Early detection of mild to moderate kidney disease is an important public health concern with regard to cognitive decline.