Blood pressure-lowering effect of melatonin in type 1 diabetes.

Our long-term goal is to determine the utility of melatonin in prevention of hypertension in type 1 diabetes. We recently reported that 5 mg melatonin taken at bedtime increases the nocturnal drop of diastolic blood pressure (BP) in adolescents with type 1 diabetes. The present study tested the hypothesis that a higher dose of melatonin, 10 mg, lowers both systolic and diastolic BP in these patients. The design was an open-label trial of 10 mg melatonin taken at bedtime daily for 7 days. Nine normotensive adolescents with type 1 diabetes, 16.2 +/- 0.3 yr old, and eight healthy controls, 16.6 +/- 0.6 yr old participated. BP was measured every 20 min by ambulatory monitoring device for 24 hr before treatment onset and on the last treatment day; sleep was monitored by diary and wrist actigraphy. Outcome measures were BP during wake, sleep and over a 24-hr period. Sleep duration and number of awakenings were used as covariates. Significance for this pilot study was set at P < 0.10. In patients with diabetes the mean BP during sleep was lower on melatonin than before treatment: systolic 104.0 +/- 2.4 and 108.4 +/- 2.4 mmHg (P = 0.085) and diastolic, 57.1 +/- 1.9 and 59.3 +/- 1.9 mmHg (P = 0.079), respectively. In controls there was no significant effect of melatonin on BP. There was no significant effect of sleep duration or number of awakenings on the BP responses. We conclude that the present results justify phase III therapeutic trials to determine the utility of melatonin in prevention of hypertension and cardiovascular complications in type 1 diabetes.