LAUSR

Cognitive impairment is common in older adults. Similarly, the prevalence of renal dysfunction is also increased in the elderly. We conducted this study to clarify the relationship between the renal function and cognitive impairment in community dwelling older adults in Korea. A cross-sectional analysis was performed on the data of the Korean Frailty and Aging Cohort Study (KFACS), a nationwide cohort study that began in 2016. Of the 3014 participants assessed in the first and second year, 2847 participants (1333 men, 1514 women) who completed baseline assessments were enrolled. The estimated glomerular filtration rate (eGFR, mL/min/1.73m2) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Renal function of the participants was classified into four groups by eGFR quartile. General cognitive function was accessed with mini-mental state exam in the Korean version (MMSE-KC). Participants who had MMSE-KC score less than 1.5 standard deviation by age, gender, and education level were regarded as the cognitive impairment. Multivariate logistic regression model was used to examine the relationship between renal function and cognitive impairment. In addition, we investigated to find the point of eGFR interval at which the odds ratio begins to increase. The mean eGFR in quartile 1 was 91.7 ± 3.22 ml/min/1.73m2, and 84.9 ± 1.81 in quartile 2, 76.1 ± 3.66 in quartile 3, and 57.2 ± 10.75 in quartile 4. In baseline characteristics, participants with lower eGFR had lower MMSE-KC scores. And the prevalence of cognitive impairment was 10.8% in quartile 1, 15.9% in quartile 2, 15.2% in quartile 3, 14.9% in quartile 4. After multivariate adjustment, the odds ratio (OR) of cognitive impairment in quartile 2 [adjusted OR: 1.569, 95% confidence intervals (CI): 1.141 - 2.158, p = 0.006] compared with quartile 1. And the odd ratios of cognitive impairment were 1.539 (95% CI: 1.113 - 2.127, p = 0.009) in quartile 3, 1.475 (95% CI: 1.062 - 2.049, p = 0.020) in quartile 4 compared with quartile 1, respectively. Among the participants with eGFR above 60 ml/min/1.73m2, the renal function was grouped by 5 ml/min/1.73m2 interval. The risk of cognitive impairment started to increase from eGFR between 80 and 85 ml/min/1.73m2 (adjusted OR: 1.667, 95% CI: 1.128 - 2.463, p = 0.010). Renal dysfunction was associated with lower global cognitive function in older adults. And the risk of cognitive impairment increased from quartile 2, especially, eGFR between 80 and 85 ml/min/1.73m2 in this population. These results suggest that mild decline of kidney function is also a risk factor of cognitive decline in the elderly.