Kidney function and cognitive performance and decline in older men

OBJECTIVES: To examine the association between kidney function and cognitive impairment and decline in elderly men. DESIGN: Observational prospective cohort. SETTING: Community based. PARTICIPANTS: Five thousand five hundred twenty-nine community dwelling men aged 65 and older (mean age 73.6 ± 5.9). MEASUREMENTS: Estimated glomerular filtration rate (eGFR) calculated using the standardized Modification of Diet in Renal Disease (MDRD) equation; cognitive function assessed using the Modified Mini-Mental State Examination (3MS) and Trail Making Test B (Trails B). RESULTS: At baseline, 148 (2.7%) and 494 (9.1%) men were classified as cognitively impaired and, in the 5-year prospective analysis, 931 (23%) and 432 (11.6%) met the criteria for cognitive decline at follow-up defined according to 3MS and Trails B performance, respectively. In unadjusted analysis, the odds of prevalent cognitive impairment and risk of cognitive decline were significantly higher in men with an eGFR less than 45 and 45 to 59 mL/min per 1.73 m² than in men with an eGFR 60 mL/min per 1.73 m² or greater. Differences in age, race, and education between eGFR categories largely explained these associations, with the exception of the association between poorer renal function and higher odds of impairment based on Trails B test score, which persisted despite adjustment for multiple potential confounders. CONCLUSION: This study found evidence of an independent association between mild to moderate reductions in kidney function and poor executive function at baseline but not with global cognitive impairment or risk of cognitive decline in older men.