Nocturnal Blood Pressure Elevation in Patients with Type 1 Diabetes Receiving Intensive Insulin Therapy Compared with that in Patients Receiving Conventional Insulin Therapy1

Studies have shown that type 1 diabetic patients may suffer from nocturnal elevation in blood pressure and that this elevation may be related to hyperinsulinemia. In this study we tested the hypothesis that tight type 1 diabetes control, which is usually accompanied by hyperinsulinemia and subclinical nocturnal hypoglycemia, may result in a higher rise in nocturnal blood pressure compared with conventional type 1 diabetes control. Eighteen patients treated with intensive insulin therapy (multiple daily injections; IIT) were compared with 18 patients treated with conventional insulin regimens (twice daily injections of regular and intermediate acting insulin; CIT). Both groups were matched for age, sex, duration of diabetes, body weight, body mass index, baseline daytime blood pressure, and microalbuminuria levels. Hemoglobin A1c was lower in the IIT group compared with that in the CIT group (8.1 ± 1.2% vs. 11.0 ± 3.2%; P < 0.01). The amount of insulin/body weight (units per kg) was higher in the IIT group than that in the CIT group (1.0 ± 0.2 vs. 0.7 ± 0.2 U/kg; P < 0.05). In all patients, a 24-h ambulatory blood pressure was recorded. The nocturnal diastolic blood pressure was higher in the IIT group (66 ± 9 mm Hg) than in the CIT group (55 ± 4 mm Hg; P < 0.01). The nocturnal decline in both systolic and diastolic blood pressure was lower in the IIT group (7 ± 5 and 6 ± 4 mm Hg, respectively) compared with that in the CIT group (13 ± 6 and 16 ± 6 mm Hg, respectively; P < 0.01). The nocturnal heart rate was higher in IIT group than in the CIT group (81 ± 12 vs. 67 ± 9/min; P < 0.05). These findings show that the intensive insulin therapy regimen may have a more deleterious effect than the conventional insulin therapy regimen on the nocturnal blood pressure of patients with type 1 diabetes.