Glucose tolerance and age-associated decline in renal function of hypertensive patients

Background Renal function is thought to decrease with age in the general po pulation, but the determinants of this age-associated evolution are poorly understood. Hypertension and diabetes mellitus, two leading causes of chron ic renal failure in the elderly, may accelerate this decline. Patients and methods Urinary clearances of [Tc-99m]diethylene triaminopenta acetic acid (DTPA) (glomerular filtration rate) and [I-131]hippuran (effect ive renal plasma flow) were assessed in 227 never-treated essential hyperte nsives aged 20-69 years. Based on the oral glucose tolerance test, the stud y population consisted of 4% patients with previously unknown diabetes mell itus, 24% with impaired glucose tolerance and 72% with normal glucose toler ance. Results When the population of 218 non-diabetic subjects was considered, gl omerular filtration rate was inversely correlated with age and arterial blo od pressure, and positively correlated with effective renal plasma flow, fi ltration fraction and fasting plasma glucose. In multivariate analysis, age and blood pressure were independent determinants of renal plasma flow, whe reas renal plasma flow, age and fasting plasma glucose were independent det erminants of glomerular filtration rate. The slope of the regression line r elating glomerular filtration rate to age was steeper in patients with impa ired glucose tolerance than in those with normal glucose tolerance (-1.52 /- 0.28 versus -0.65 +/- 0.12, P < 0.01). Conclusions These results suggest that impaired glucose tolerance, which is seldom searched for in patients with essential hypertension, may be an imp ortant determinant of the age-associated decline in renal function. J Hyper tens 19:2257-2264 (C) 2001 Lippincott Williams & Wilkins.