Cognitive status in chronic kidney disease elderly patients

Background: Chronic Kidney disease (CKD) in elderly patients leads to dementia and cognitive impairment which leads to functional dependence and recurrent hospitalization. Objective: To assess different cognitive domains in CKD elderly patients. Methods : A prospective observational study conducted in Ain-Shams University hospital outpatient clinics. A total of 100 CKD patients, elderly aged 60 years and older with estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m 2 and not on renal replacement therapy were enrolled in the study. The Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuropsychological battery was utilized to assess cognitive functions domains (executive functions, language functions, verbal learning, visuospatial functions, delayed recall, memory consolidation, and recognition memory) for 100 CKD patients visited Ain Shams University hospital outpatient clinics who scored > 24 in the Mini-mental state examination (MMSE.) Results: CKD patients had low mean MMSE and mean verbal fluency while language functions score had not been affected. There was a significant positive correlation (p< 0.001) between the mean eGFR and the CERAD total score. Conclusion: CERAD total score was positively correlated to eGFR in CKD patients confirming the association between cognition and renal impairment. Age and educational level significantly affect cognitive performance.


INTRODUCTION
Chronic kidney disease (CKD) is a disease affecting the central nervous system [1].Elderly CKD patients have cognitive impairment, dementia [2] and depression [3] which reduce quality of life [4].Cognition decline can be manifested from mild cognitive impairment (MCI), up to clinically relevant dementia, interfering with daily life and independence [1].Cognitive impairment that occurs with MCI exceeds the normal ageing decline [5].MCI shows mild impairment in different cognitive domains: executive functions of memory (attention and learning), problem solving (processing) and self-control (depression and emotion) [6].These can be screened by neuropsychological batteries.The CERAD test battery (The Consortium to Establish a Registry for Alzheimer's Disease) was evolved for diagnosis of cognitive impairments occurs with early Alzheimer's disease (AD) [7].It was used after which for diagnosis of cognitive impairment in general.It is reliable, valid and have inter-rater agreement [8].It measures 8 items: executive functions, language functions, verbal learning, visuospatial functions, delayed recall, memory consolidation, and recognition memory.Delayed recall of the wordlist and the saving scores (such as delayed recall adjusted for acquisition) on the CERAD are impaired in mild AD but preserved in normal aging [9][10][11].MCI should be diagnosed in CKD patients before irreversible damage occurs.

OBJECTIVE
The aim of this study was to assess different cognitive domains in CKD elderly patients.CDR was used to assess cognitive impairment in six areas: community affairs, home & hobbies, judgment & problem solving, memory, orientation, and personal care.Each domain is graded on 5-point scale: 0 for no impairment; 0.5 for mild cognitive impairment; 1 for mild dementia; 2 for moderate dementia; and 3 for severe dementia [16].The global CDR score was calculated using the Washington University web algorithm (http://www.biostat.wustl.edu/~adrc/cdrpgm/index.html).

Statistical methods
Quantitative data was expressed as mean, standard deviation while qualitative data was expressed as frequencies and percentages.Comparison between quantitative variables was done using t-test.IBM SPSS statistics for windows version 23 (IBM Corp., Armonk, NY, USA) was used for data analysis.Pearson correlation coefficient was used in analysis of this study A "P value" of less than 0.05 was considered statistically significant.

RESULTS
The study was conducted on 100 elderly patients with CKD, mean age 68.0 (± 6.1).61% of the participants were males and 39% were females.Demographic, clinical background data are shown in Table 1.

Table (1) Demographic and clinical characteristics of the studied CKD patients
Others: Osteoarthritis.ESRD= End-Stage renal disease.Illiterates: who cannot read or write or <4 years of education; read and write: ≥4 years of education; primary education: completed 6 years of formal education; secondary education: completed 12 years of formal education; college: 16 years of education Table 1 shows that 17% of the CKD cases were in stage 3A (mild), 32% in stage 3B (moderate) and 30% in stage 4 (advanced)while 21%of cases are in stage 5 (pre-dialysis).Also, there is high percentage of diabetes and hypertension among CKD patients.4) shows a significant negative correlation between the mean total CERAD total score and the mean age.There is a significant positive correlation between the level of education of the patients and the CERAD total score.The higher the educational level the better CERAD total scores and performance.There is a significant positive correlation between the mean eGFR and the CERAD total score, poorer cognitive tests performance were expected in sever renal impairment.There is no statistically significant correlation between the CERAD total score and the mean serum creatinine or the stage of the CKD.