Diuretics and beta-blockers, used to treat hypertension, are associated with an increased risk of developing type 2 diabetes, new findings indicate.

“The relation between the use of different classes of antihypertensive medications and the risk of incident type 2 diabetes is unclear,” Dr. Eric N. Taylor, of Harvard Medical School, Boston, and colleagues write in the medical journal Diabetes Care. “Prior studies have reported conflicting results.”

The researchers examined the issue using data from studies that followed three large groups of women and men: the Nurses’ Health Study (NHS) I and II and the Health Professionals Follow-up Study (HPFS).

The analysis included 41,193 older women from NHS I, 14,151 younger women from NHS II, and 19,472 men from HPFS. All of the subjects had high blood pressure, but not diabetes initially, and were followed for 8, 10, and 16 years, respectively.

A total of 3589 new cases of type 2 diabetes were recorded during follow-up.

The risk of developing diabetes in subjects taking thiazide-type diuretics compared with those not taking a thiazide was increased by 20 percent in older women, 45 percent in younger women, and 36 percent in men, after taking account of age, weight, physical activity, and other risk factors.

Compared to patients not taking a beta-blocker, older women taking beta-blockers had a 32 percent higher risk of diabetes, while for men the risk was 20 percent higher.

“Increased surveillance for diabetes in patients treated with these medications may be warranted,” the authors conclude.

The use of other common types of blood pressure lowering drugs - calcium channel blockers and ACE inhibitors - was not associated with the development of type 2 diabetes, according to the report.

SOURCE: Diabetes Care, May 2006.