Chronic kidney disease and cognitive impairment among the very old in China

Previous studies have confirmed that chronic kidney disease (CKD) influences the cognitive function of adults. However, few studies focused the relationships among the very old. The purpose of this study was to determine whether CKD is associated with cognitive impairment among nonagenarians and centenarians in China.

This work was conducted as a cross-sectional study. 767 unrelated Chinese nonagenarians and centenarians participated in the study. The 30-item mini-mental state examination (MMSE) was used to assess cognitive function. Estimated glomerular filtration rate (eGFR) was estimated using the Modification of Diet in Renal Disease equation (Chinese version). CKD was defined as eGFR less than 60 mL/min/1.73 m(2).

The cohort was 68.2 % female and mean (SD) age was 93.8 (3.5) years. There were 113 (14.7 %) and 577 (75.2 %) prevalent cases of CKD and cognitive impairment, respectively. After adjusting for sociodemographic variables, multivariate logistic regression showed CKD was not significantly associated with cognitive impairment (OR 0.81, 95 % CI 0.49-1.33). When other disease-related variables were adjusted, the result remained substantially unchanged. However, age, gender, education and income may largely or entirely explain the lack of association between CKD and cognitive impairment as measured according to the MMSE.

Among Chinese nonagenarians and centenarians, CKD was not directly correlated with cognitive impairment.