AGE AS A DETERMINANT OF GLOMERULAR-FILTRATION RATE IN NON-INSULIN-DEPENDENT DIABETES-MELLITUS

Background. The level of glomerular filtration rate (GFR) and its dete rminants in non-insulin-dependent diabetes mellitus (NIDDM) are curren tly controversial. Design of the study. We measured GFR and effective renal plasma flow (ERPF) in 121 consecutive NIDDM without evidence of overt diabetic nephropathy. Age varied from 28 to 70 years, 61.2% were women and known duration of NIDDM was 0 - 37 years. Hypertension was detected in 36.4% of patients and 47.8% had microalbuminuria. Results. An inverse correlation was found between GFR and age, but not with kn own duration of NIDDM. It was a weak correlation (r = -0.41) but stati stically significant (P < 0.001). The other variables considered were not significant by multiple stepwise regression analysis, but patients with lower GFR tended to have diabetic retinopathy more frequently. G FR was lower in hypertensive compared to normotensive patients (123 +/ - 28.4 versus 136 +/- 32.5 ml/min/1.73 m(2); P < 0.05), but was not di fferent between patients with normal and elevated albumin excretion ra te. ERPF also had an inverse correlation with age (r = -0.45, P < 0.00 1). Conclusion. We conclude that (i) age should be considered as a con founding variable when evaluating GFR in patients with NIDDM, and (ii) the age-dependent decline in GFR may mask hyperfiltration in the earl y stages of diabetic nephropathy in NIDDM.