Objective: To assess renal function in various groups of elderly persons, and to determine the proportion of patients with clinically important renal impairment.
Design: Cross-sectional study.
Participants: Three geriatric populations aged 70 years and over, representing increasing levels of care/treatment: community-dwelling elderly referred to a geriatric outpatient department, inpatients on a geriatric ward, and nursing home patients.
Main outcome measures: Cockroft and Gault's formula was applied to calculate glomerular filtration rate (GFR). Differences in GFR between age groups and between care levels were explored.
Results: Altogether 288 elderly persons were included in the study. We observed a general age-related decline of renal function. Only 2% of the participants had normal renal function (GFR >90 ml/min), 13% had light (GFR 60-89 ml/min), 68% moderate (GFR 30-59 ml/min), and 17% severe (GFR 15-29 ml/min) impairment in GFR. Moderate or severely decreased GFR was observed in 75% of the outpatients, 78% of the patients from the geriatric ward, and 91% of the nursing home patients. Altogether 99% of patients aged 85+ had renal impairment necessitating dosing adjustment for drugs that are mainly eliminated through renal excretion.
Conclusion: Clinically important renal impairment is common in old age, especially in the frailest elderly living in nursing homes. This finding underlines the necessity for close supervision of drug treatment based on renal function in old age.