Beta-blockers raise risk of diabetes

Experts differ on interpreting the message

Beta-blockers increase the risk of diabetes by about 28%, say Johns Hopkins University researchers, who add their data indicate a lower risk associated with the popular antihypertensive medication than was shown by earlier studies.

While those who conducted the study say the results should be considered encouraging, the findings have raised red flags for others who suggest clinicians should screen for Type 2 diabetes risk factors before prescribing beta-blockers.

"This is not a bad message for beta-blockers," says lead author Todd Gress, MD, MPH, who conducted the study as a fellow at Johns Hopkins Medical School in Baltimore. "It’s a positive message, especially compared to a few studies that have shown the increased risk of diabetes in patients taking beta-blockers could be 10 times more than we found."

Can help screen those at high risk

Gress, who is now an assistant professor of medicine at Marshall University in Huntington, WV, notes that beta-blockers "seem to be of great benefit" in people who already have diabetes.

While it is well known that hypertension is a risk factor for diabetes, Gress’ results of 12,550 patients in the Atherosclerosis Risk in Communi-ties (ARICV) showed that patients who had hypertension and got no medication were at the same risk for developing diabetes as those who took the beta-blockers. The study appeared in the March 30 New England Journal of Medicine.

Researchers found no risks of diabetes associated with calcium channel blockers and ACE inhibitors, both of which are widely and successfully used to treat hypertension.

Gress says his results should not dissuade physicians from prescribing beta-blockers to treat hypertension because they can readily screen for those at high risk. "The use of beta-blockers appears to increase the risk of diabetes, but this adverse effect must be weighed against the proven benefits of beta-blockers in reducing the risk of cardiovascular events."

Gress says his team did not discover the mechanism by which beta-blockers increase the risk. Researchers initially theorized that the drug might slow metabolism, causing weight gain, but the study showed no weight gain associated with beta-blockers.

Om Ganda, MD, director of the lipid clinic at Joslin Diabetes Center in Boston and associate professor of medicine at Harvard Medical School says Gress’ results are "cause for alarm."

His advice: "If you’re going to treat people with hypertension, consider the options in those at risk for diabetes, especially those with a family history of diabetes."

Ganda says he does not use beta-blockers as a drug of first choice because of the risk of diabetes developing where it might not have developed without the drugs. He also says that all beta-blockers may not act alike, and suggests further study.

ACE inhibitors are top choice

Antihypertensive drugs have been "life savers," Ganda says, but calcium channel blockers and ACE inhibitors may be better treatment choices simply because they are not associated with the development of diabetes.

Gress even found evidence that patients taking ACE inhibitors and calcium channel blockers lowered their mean blood sugars. Ganda says ACE inhibitors are his first-choice drug.

While beta-blockers don’t seem to have adverse effects in treating patients already diagnosed with diabetes, there is some evidence they can cause a delay in recovering from hypoglycemia, Ganda says.

For physicians who want to change medications for patients on beta-blockers, Ganda says they should not be abruptly stopped. "Taper them off for a few weeks and then start another drug."

[Contact Todd Gress at (304) 691-1093 and Om Ganda at (617) 732-2400.]