The association between diurnal blood pressure variation and diabetic nephropathy was assessed in four groups of Type 1 (insulin-dependent) diabetic patients who underwent 24-h ambulatory blood pressure monitoring using an oscillometric technique. Patients with nephropathy, who had never been treated for hypertension (group D3, n = 13), were individually matched for age, sex and diabetes duration to a group of microalbuminuric patients (D2, n = 26), to normoalbuminuric patients (D1, n = 26) and to healthy control subjects (C, n = 26). Group D3 was also compared to patients with advanced nephropathy receiving treatment for hypertension, mainly a combination of angiotensin converting enzyme inhibitors, metoprolol and diuretics (D4, n = 11). In group D3 24-h diastolic blood pressure (85 +/- 8 mmHg) was comparable to the results obtained in D4 (85 +/- 8 mm Hg) but significantly higher than in D2 (78 +/- 7 mmHg), D1 (73 +/- 7 mm Hg) and C (73 +/- 7 mmHg, p < 0.05, Tukey's test). The night/day ratio of diastolic blood pressure was higher in D3 (86 +/- 5 %) and D2 (85 +/- 7 %) than in C (80 +/- 7 %, p < 0.02). This ratio was also elevated in group D4 (94 +/- 8 % ) compared to D3 (p < 0.05) corresponding to a marked smoothing of the diurnal blood pressure curve. The 24-h heart rate (beats per min) was significantly elevated in D3 (84 +/- 8) and D2 (80 +/- 10) compared with C (73 +/- 11, p < 0.05 Tukey's test), suggesting the presence of parasympathetic neuropathy. In conclusion the normal circadian variation of blood pressure was moderately disturbed in a group of microalbuminuric patients and patients with less advanced overt nephropathy. Patients with advanced diabetic nephropathy receiving antihypertensive therapy showed a marked reduction of nocturnal blood pressure fall, which can only be identified by the application of ambulatory blood pressure measurements to verify the 24-h effectiveness of blood pressure control.
