Nondipping of Nocturnal Blood Pressure Is Related to Urinary Albumin Excretion Rate in Patients With Type 2 Diabetes Mellitus

Although cardiovascular and cerebrovascular morbidity and mortality in type 2 diabetic patients is closely related to urinary albumin excretion rate (UAER), the causative mechanisms are not yet identified. The aim of our study was to define the circadian variation of blood pressure (BP) in 72 type 2 diabetic patients (mean age 60 years, mean diabetes mellitus duration: 12 years) in comparison with 41 nondiabetic controls with essential hypertension (mean age 58 years) by using ambulatory blood pressure measurement. Thirty diabetic patients had normal UAER (< 30 mg/24 h), 27 had microalbuminuria (30 to 300 mg/24 h), and 15 had persistent proteinuria (> 300 mg/24 h). Systolic blood pressure during both nighttime and daytime was significantly elevated in type 2 diabetic patients with macroalbuminuria compared to controls and patients with normal UAER. During nighttime even type 2 diabetic patients with microalbuminuria had significantly elevated systolic blood pressure compared to controls with essential hypertension. We also observed a correlation of nocturnal blood pressure to UAER (systolic: r = 0.32, P < .007 and diastolic: r = 0.24, P < .04). Nondipping (defined as a reduction of nocturnal BP < 10%) was observed in 80% of the macroalbuminuric, 74% of the microalbuminuric, but only in 43% of the normoalbuminuric type 2 diabetic patients and in 37% of the controls (P < .04). Since a loss of circadian variation of BP is closely related to vascular complications in nondiabetics, our findings may indicate an important relationship between nondipping of BP and the high morbidity and mortality rate in diabetic patients with increased UAER.