Adrenergic blockade improved insulin resistance in patients with morning hypertension: the Japan Morning Surge-1 study

BACKGROUND: It has been demonstrated that insulin resistance is associated with morning hypertension. We investigated the hypothesis that the lowering of morning blood pressure (BP) can improve insulin resistance in patients with morning hypertension. METHODS: In the present study, 611 treated hypertensive patients with morning hypertension were randomized into either a doxazosin group, for whom a once-daily bedtime dose of doxazosin was added to the current medication regimen, or a control group, who continued their current medication. The homeostasis model assessment of the insulin resistance index (HOMA-IR) was performed at baseline and the 6th month of treatment. The associations between change in HOMA-IR and changes in systolic BP (SBP) measures were assessed by multiple regression analyses with adjustment for covariates. RESULTS: HOMA-IR was significantly decreased in the doxazosin group (2.1 +/- 3.0 to 1.8 +/- 2.6, P = 0.04) but not in the control group. The change in HOMA-IR was significantly associated with the change in morning SBP (r = 0.10, P = 0.02) but not with evening SBP. In multiple regression analysis, the change in HOMA-IR was independently and significantly associated with the change in morning SBP (beta = 0.15, P = 0.016) but not with the change in evening SBP. CONCLUSION: In patients with morning hypertension, specific treatment for morning hypertension with an adrenergic blockade has a beneficial effect on insulin resistance.