Significant negative association with age and both GFR and ERPF in male and female living kidney donors

Abstract

Sir, Berg reports that glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were unrelated to age in 62 female potential kidney donors, whereas in 60 male potential donors, GFR and ERPF were lower in older subjects [1]. They conclude that effects of ageing on the kidney are gender-related. This conclusion, however, is not warranted without longitudinal data. Moreover, the agerange in their study was relatively narrow, with few subjects aged over 50. Furthermore, subjects evaluated for kidney donation represent a healthier-than-average population, in whom risk factors for renal function loss over time are less prevalent [2]. Finally, the number of subjects studied was relatively small. These factors weaken the power to detect age effects on renal function. We, therefore, analysed our donor screening data (GFR: I-iothalamate, ERPF: I-hippurate) in 84 male (mean age 48, range 21–75) and 136 female (mean age 48, range 20–70) subjects. In contrast to the data by Berg [1], a negative correlation between age and GFR and between age and ERPF was present not only in men, but also in women (Figure 1). The correlations persisted after exclusion of subjects aged over 50. Filtration fraction rose with age in men (R1⁄4 0.390, P< 0.0001) but not in women (R1⁄4 0.046, P1⁄4 0.596), supporting the relevance of gender for age-related effects on the kidney. Longitudinal studies are required to elucidate the impact of gender on the natural course of renal function during ageing and its mechanisms.