Kidney Function and Cognitive Impairment in US Adults: The Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study

Background

The association between kidney function and cognitive impairment has not been assessed in a national sample with a wide spectrum of kidney disease severity.

Study Design

Cross-sectional.

Setting & Participants

23,405 participants (mean age, 64.9 ± 9.6 years) with baseline measurements of creatinine and cognitive function participating in the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study, a study of stroke risk factors in a large national sample.

Predictor

Estimated glomerular filtration rate (eGFR).

Outcome

Cognitive impairment.

Measurements

Chronic kidney disease (CKD) was defined as eGFR less than 60 mL/min/1.73 m². Kidney function was analyzed in 10-mL/min/1.73 m² increments in those with CKD, and in exploratory analyses, across the range of kidney function. Cognitive function was assessed using the 6-Item Screener, and participants with a score of 4 or less were considered to have cognitive impairment.

Results

CKD was associated with an increased prevalence of cognitive impairment independent of confounding factors (odds ratio, 1.23; 95% confidence interval, 1.06 to 1.43). In patients with CKD, each 10-mL/min/1.73 m² decrease in eGFR less than 60 mL/min/1.73 m² was associated with an 11% increased prevalence of impairment (odds ratio, 1.11; 95% confidence interval, 1.04 to 1.19). Exploratory analyses showed a nonlinear association between eGFR and prevalence of cognitive impairment, with a significant increased prevalence of impairment in those with eGFR less than 50 and 100 mL/min/1.73 m² or greater.

Limitations

Longitudinal measures of cognitive function were not available.

Conclusions

In US adults, lower levels of kidney function are associated with an increased prevalence of cognitive impairment. The prevalence of impairment appears to increase early in the course of kidney disease; therefore, screening for impairment should be considered in all adults with CKD.

Index Words: Chronic kidney disease (CKD), cognitive function, cognitive impairment