A decrease in glomerular filtration rate with aging: the effect of smoking and obesity

Jung, Soo Suk; Lhee, Hyun Young; Kim, Hyang; Lee, Kyu Beck; Ryu, Seung Ho

Abstract

BACKGROUND: The kidney function with aging is the dramatic changes of human organ system. Recent studies have suggested that many risk factors such as smoking and obesity could contribute to the progression of chronic kidney disease, though there is a little evidence in the literature showing this relationship in the general population prospectively. We aimed to identify the change of calculated glomerular filtration rate (GFR) with aging in healthy adults and to evaluate the effect of prior risk factors to the change of GFR after 5 years follow-up.
METHODS
This study included 3,928 healthy adults who participated in health screening examinations in 1997 and 2002. Average age was 42 +/- 5 years in 2002 (2,955 males, 973 females). The study population had no diabetes, hypertension, renal disease and other major diseases. The clinical and laboratory monitoring were performed each on 1997 and 2002; 5 years follow-up. In this study population, GFR was calculated using the MDRD (Modification of Diet in Renal Disease) equation: calculated GFR = 186 X Scr(-1.154) X age(-0.203) X (0.742 if female). We evaluated the change of calculated GFR with aging and compared the change of calculated GFR after 5 years follow-up according to smoking and obesity.
RESULTS
The decreased GFR in adults was associated with aging. The mean calculated GFR (mean +/- SD) was 82.2 +/- 9.7 mL/min/1.73 m2 at 1997, 76.2 +/- 9.1 mL/min/1.73 m2 at 2002, respectively, so decrease is 6.0 mL/min/1.73 m2/yr (1.2 mL/min/1.73 m2/yr). The change of calculated GFR was more decreased in smoking group (5.2 vs 5.0 mL/min/1.73 m2) and obesity group (6.4 vs 5.7 mL/min/1.73 m2), but not statistically significant(p>0.05).
CONCLUSION
Aging is an important factor of decrease in renal function. The mean decrease in calculated GFR was 1.2 mL/min/1.73 m2/yr. We suggest that smoking and obesity had some effects on decrease in renal function. These changes in renal function should be confirmed by a prospective study for a long period and in a large number of subject.