People with high blood pressure are two and a half times more likely to develop Type 2, or noninsulin-dependent, diabetes as those with normal blood pressure, according to a study led by researchers at Johns Hopkins and published in the March 30 issue of The New England Journal of Medicine.
The study also found the risk of diabetes to be 28 percent greater among patients who took beta blockers--medications to reduce heart rate and the heart's output of blood--than those who took no medication. Contrary to previous studies, however, the risk of diabetes among hypertensive patients taking thiazide diuretics was found to be lower than that of people not taking them.
"We're not suggesting that doctors stop prescribing beta blockers as they have proven benefits in lowering the risk of cardiac events," says Frederick L. Brancati, associate professor of medicine and epidemiology at Hopkins. "But physicians need to weigh the benefits against the diabetes risk and monitor patients carefully.
"Physicians also should not be discouraged from prescribing thiazide diuretics, as our study did not find a causal link to diabetes. These are good medications to prevent heart disease and stroke."
As part of an ongoing study called Atherosclerosis Risk in Communities, researchers analyzed nationwide data on 12,550 adults ages 45 to 64 who either had heart disease or were at risk for developing it. None had diabetes at the outset.
Patients underwent an extensive health evaluation at the study's start. Incidence of diabetes was assessed among the group after three years and again after six years.
During six years of follow-up, there were 1,146 new cases of diabetes. Of these, 569 occurred in patients with high blood pressure and 577 in people with normal blood pressure. Among the 3,804 adults who had high blood pressure at the study's start, those taking beta blockers were 28 percent more likely to develop diabetes than their counterparts not taking medication.
Among patients taking high blood pressure medications, those taking diuretics, angiotensin-converting-enzyme inhibitors or calcium-channel antagonists were not at increased risk of diabetes. Angiotensin-converting-enzyme inhibitors interfere with the body's production of angiotensin, a chemical that causes the arteries to constrict. Calcium channel blockers reduce heart rate and relax blood vessels.
The study was supported by the National Institutes of Health and the American Heart Association. Other Hopkins authors were Todd W. Gress and F. Javier Nieto.