Assessment of renal function in elderly with dementia is a difficult clinical problem due to the high prevalence of malnutrition and creatinine limits as a marker of glomerular filtration in this context.

To assess the correlation between renal function and dementia diagnosis.

To highlight differences between methods of assessment of renal function based on creatinine and cystatin C.

Cross-sectional study. Patients institutionalized at Bucharest City-Center of Socio-Medical Services (a nursing home) from 04/2014 to 11/2014 were included in the study. Dementia diagnosis was established by a psychiatrist. We determined serum creatinine by Jaffe method and serum cystatin C by nephelometry. Renal function was determined using several formulas based on serum creatinine/cystatin C: Cockcroft–Gault, MDRD, creatinine CKDEPI/cystatin/creatinine + cystatin, Berlin Initiative Study (BIS1, BIS2), Lund-Malmo LM-LBM. To highlight a link between dementia and renal function, we determined Spearman correlation coefficients.

Thirty-one patients were included in the study, mean age 78.6 (63–97) years, 64% women. The diagnosis of dementia (1 = positive, 0 = negative) had the following statistically significant correlations: CKDEPIcystatin: rho = –0.390, P = 0.015; CKDEPI creatinine-cystatin: rho = –0.332, P = 0.032; BIS2: rho = –0.346, P = 0.02. We did not find statistically significant correlations between the diagnosis of dementia and formulas for assessing renal function based on creatinine only.

Elderly patients with dementia present decreased kidney function as determined by formulas based on cystatin/cystatin + creatinine, but not on creatinine alone. Assessment of renal function using cystatin C might represent a useful method for detection of renal dysfunction in these patients and for proper dosage of medication.

The authors have not supplied their declaration of competing interest.