Impact of Arterial Blood Pressure and Albuminuria on the Progression of Diabetic Nephropathy in IDDM Patients

Abstract

To evaluate the impact of systemic blood pressure and albuminuria on the progression of diabetic nephropathy, we followed 41 IDDM patients with persistent albuminuria (> 300 mg/24 h) by measuring glomerular filtration rate (⁵¹Cr-EDTA technique), blood pressure, and albuminuria. None of the patients were taking drugs other than insulin. Arterial blood pressure, albuminuria, and blood glucose were measured four to eight times/yr, whereas glomerular filtration rate was determined twice yearly. During the median investigation period of 36 (15–66) mo, glomerular filtration rate decreased from 102 ± 23 to 83 ± 27 ml · min⁻¹ · 1.73 m⁻² (P < 0.001), albuminuria increased from 633 to 1435 μg/min (P < 0.001), and blood pressure rose from 133/85 ± 10/9 to 149/93 ± 8/11 mmHg (P < 0.001). Univariate analysis revealed a significant correlation between the rates of decline in glomerular filtration rate and diastolic blood pressure (r = 0.52, P < 0.01) and glomerular filtration rate and albuminuria (r = 0.34, P < 0.02). But stepwise multiple linear regression analysis only showed a significant correlation between the rate of decline in glomerular filtration rate and diastolic blood pressure (P < 0.01). In patients with diastolic blood pressure below the mean value of 89 mmHg, stepwise multiple regression analysis showed that albuminuria and not blood pressure was correlated significantly with rate of decline in glomerular filtration rate. Patients were stratified by average value of diastolic blood pressure measured during the investigation period. Patients in the lowest fertile had a rate of decline in glomerular filtration rate of 4.3 ± 4 ml · min⁻¹ · yr⁻¹ compared with the middle and the highest tertiles of 7.7 ± 5 and 10.1 ± 5 ml · min⁻¹ · yr⁻¹, respectively (P < 0.01). The average diastolic blood pressure in the three groups was 81, 89, and 98 mmHg, respectively. This study suggests that systemic blood pressure elevation and albuminuria accelerate the progression of diabetic nephropathy. The latter progression promoter seems only to play a role in patients with normotension (diastolic blood pressure <89 mmHg).