The cross-sectional association of renal dysfunction with tests of cognition in middle-aged adults with early type 2 diabetes: The GRADE Study

Objective: The association of renal dysfunction with tests of cognition in type 2 diabetes has been examined in individuals with moderate and advanced renal disease. Here we examine the association of renal dysfunction with tests of cognition in a cohort of middle-aged adults with short duration diabetes (mean 4.0 ± 2.8 years). Methods: Baseline data were examined from the Glycemia Reduction Approaches in Diabetes (GRADE) study (n = 4998). Renal dysfunction was defined by the presence of albumin in the urine or by estimated glomerular filtration rate (eGFR). Cognition was assessed with the Spanish English Verbal Learning Test, Letter and Animal fluency tests, and the Digit Symbol Substitution Test. Results: Participants with albuminuria or eGFR <60 ml/min/1.73 m² had significantly lower test scores of information processing speed and perception, executive function and ability to categorize information, and of verbal learning and memory compared to participants without renal disease. Adjustment for hypertension, dyslipidemia, and waist circumference attenuated many of these findings but markers of impaired learning and executive function continued to remain lower in association with higher urine albumin levels. Conclusion: In type 2 diabetes of short duration, there are already subtle deficiencies in markers of cognition in association with renal disease in middle aged adults.