Early markers of kidney dysfunction and cognitive impairment among older adults.
BACKGROUND
Age-related decline in kidney function can be an important risk factor for cognitive impairment in older adults. In this study, we examined several kidney function measures for the association with cognitive function in older adults in hope to identify early and sensitive markers that can be used for the detection or screening for cognitive impairment.


METHODS
A total of 1982 older participants (aged ≥60years) in the 1999-2002 National Health and Nutrition Examination Survey was analyzed for the association between kidney function and cognitive impairment using multivariate logistic regression and general linear models. Cognitive functioning was assessed during the household interview using a version of the Digit Symbol Substitution Test of the Wechsler Adult Intelligence Scale III. In our study, participants with a score of <31, the 25th percentiles of the distribution, or who were unable to complete the sample exercise due to cognitive limitations were classified as having cognitive impairment.


RESULTS
Of 1982 older adults, 503 were having cognitive impairment (weighted prevalence, 15.38%). Among the kidney function measures that we examined, the levels of serum cystatin C and urinary albumin were found being significantly associated with cognitive impairment after adjusting for age, sex, race/ethnicity, poverty status, education, physical activity, BMI, cigarette smoking, and alcohol consumption. Cognitive functioning scores were significantly decreasing with increasing levels of kidney dysfunction markers.


CONCLUSIONS
Serum cystatin C and urinary albumin that are early markers of chronic kidney disease might serve as early and effective markers for cognitive decline in older adults. Mechanisms underlying the observed association need to be further characterized.
Department of Community Medicine, Mercer University School of Medicine, Macon, GA, USA. Electronic address: wei_yd@mercer.edu.
Yudan
Y
Wei
Medical College of Georgia, Augusta University, Augusta, GA, USA.
Yinan Kevin
YK
Wei
Department of Mathematics and Computer Science, Fort Valley State University, Fort Valley, GA, USA.
Jianmin
J
Zhu
D000368:Aged; D000375:Aging / Q000097:blood; D000419:Albuminuria / Q000378:metabolism*; D003072:Cognition Disorders / Q000378:metabolism*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D016017:Odds Ratio; D051436:Renal Insufficiency, Chronic / Q000097:blood*; D012189:Retrospective Studies; D012720:Severity of Illness Index
D055316:Cystatin C
Cognitive impairment; Kidney dysfunction; Older adults; Serum cystatin C; Urinary albumin