[Role of nocturnal blood pressure in the onset of diabetic nephropathy].

Unlabelled: The aim of this study was to assess the responsibility of night-time blood pressure in the onset of nephropathy in diabetic patients.

Patients and methods: This study included 98 diabetic patients (mean age: 54 +/- 15 years, diabetes duration: 15 +/- 10 years). An evaluation of diabetes and a 24-h ambulatory blood pressure were performed at the initial evaluation (Y0) and about five years later (Y5). At Y0, all patients had normal urinary albumin excretion (UAE) (<30 mg/24h). They were separated into two groups according to urinary albumin excretion at Y5: group (N +): UAE>30 mg/24h and group (N-): UAE<30 mg/24h. Twenty four hours ambulatory blood pressure, clinical and biological parameters recorded at Y0 were compared in both.

Results: At Y5, there was 18 patients in group (N +) and 78 in group (N-). Patients of group (N +) were older than those of group (N-): 62.9 +/- 9.5 vs. 52.6 +/- 15.7 years, p<0.01, and their BMI was higher (28 +/- 5 vs. 25 +/- 4 kg/m2, p<0.03). Diabetes duration and Hb A1c levels did not differ from significant manner in both. At Y0, UAE was significantly higher in group (N +) than in group (N-): 13 +/- 7 vs. 8 +/- 6 mg/24h, p<0.01. At the initial evaluation, daytime systolic and diastolic blood pressures did not differ from significant manner in both. Systolic and diastolic BP night-time were higher in diabetic patients who developed microalbuminuria (SBP: 122 +/- 19 vs. 113 +/- 13 mmHg, p<0.05 and DBP: 70 +/- 6 vs. 65 +/- 10 mmHg, p<0.03). UAE collected at Y5 was correlated to night-time BP recorded at Y0 (SBP: r=0.381, p=0.001 and PAD: r=0.294, p=0.004) and night-time systolic BP explained 12.3% of the UAE variance. Progression of UAE between the two evaluations was found to be correlated to the night-time systolic BP recorded at Y0 (r=0.335, p=0.0008) and night-time systolic BP explained 11.7% of the progression variance. There was a negative correlation between UAE at A5 and the difference between daytime and night-time BP recorded during the same evaluation (r=- 0.230, p=0.024 with SBP and r=- 0.243, p=0.017 with DBP).

Conclusion: The results underlign the resposability of night-time blood pressure, and more especially of nighttime systolic blood pressure, for the onset of nephropathy in diabetic patients.