Insulin Therapy, Hyperglycemia, and Hypertension in Type 1

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Study Question: What are the long-term blood pressure effects of glucose-lowering therapy and hyperglycemia?
Methods: The authors examined the effects of intensive insulin therapy and hyperglycemia on the development of hypertension in the Diabetes Control and Complications Trial (DCCT) and its observational follow-up, the Epidemiology of Diabetes Intervention and Complications (EDIC) study. Incident hypertension was defined as two consecutive study visits with a systolic blood pressure of 140 mm Hg or higher, a diastolic blood pressure of 90 mm Hg or higher, or use of antihypertensive medications to treat high blood pressure.
Results: Participants were enrolled from August 23, 1983, through June 30, 1989. During a 15.8-year median follow-up, 630 of 1,441 participants developed hypertension. During the DCCT, the incidence of hypertension was similar, comparing participants assigned to intensive versus conventional therapy. However, intensive therapy during the DCCT reduced the risk of incident hypertension by 24% during the EDIC study follow-up (hazard ratio, 0.76; 95% confidence interval [CI], 0.64-0.92). A higher hemoglobin A1c level, measured at baseline or throughout follow-up, was associated with increased risk for incident hypertension (adjusted hazard ratios, 1.11 [95% CI, 1.06-1.17] and 1.25 [95% CI, 1.14-1.37], respectively, for each 1% higher hemoglobin A1c level), and glycemic control appeared to mediate the antihypertensive benefit of intensive therapy. Older age, male sex, family history of hypertension, greater baseline body mass index, weight gain, and greater albumin excretion rate were independently associated with increased risk of hypertension.
Conclusions: The authors concluded that hyperglycemia is a risk factor for incident hypertension in type 1 diabetes, and intensive insulin therapy reduces the long-term risk of developing hypertension.
Perspective: The results of this study suggest that hyperglycemia contributes to the pathogenesis of hypertension in people with type 1 diabetes mellitus. Prevention of hypertension appears to be an additional long-term benefit of intensive insulin therapy. Clinicians need to consider that the protective effect of intensive insulin therapy on blood pressure occurs over a relatively long period, and the beneficial effects of glucose lowering may be counterbalanced by unmeasured adverse effects of intensive insulin therapy in the short-term. Debabrata Mukherjee, M.D., F.A.C.C.