Diabetes ups risk of abnormal heart rhythm

People with diabetes are at increased risk of a common type of abnormal heart rhythm known as atrial fibrillation, new research shows.

This risk gets worse the longer a person has been taking medications for diabetes, while poor blood sugar control also exacerbates risk, Dr. Sascha Dublin of the Group Health Research Institute in Seattle and her colleagues found.

Atrial fibrillation is not in and of itself deadly, Dublin noted in an interview with Reuters Health, but it does increase a person's risk of stroke and heart failure.

Studies examining the relationship between diabetes and atrial fibrillation have yielded mixed results, and often didn't take obesity into account. This is important, Dublin noted, because obesity increases both diabetes risk and atrial fibrillation risk. "We felt that the literature really was in a state of uncertainty," Dublin said.

In the current study, Dublin and her team looked at data from Group Health, a large healthcare delivery system, on 1,410 people diagnosed with atrial fibrillation and 2,203 people without the abnormal heart rhythm. Eighteen percent of the people with atrial fibrillation were taking medications for diabetes, compared to 14 percent of the controls. This translated into a 40 percent increased risk of atrial fibrillation for the treated diabetics.

And the more severe a person's diabetes was, the greater their risk of atrial fibrillation. To gauge diabetes severity, the researchers used two measurements: average hemoglobin A1C levels, a standard indicator of blood sugar control over many years; and the amount of time a person had been on medicines for diabetes.

Atrial fibrillation risk rose as people's blood sugar control worsened, the researchers found. While the risk was only about 6 percent greater for people with A1C levels of 7 or less, indicating good long-term blood sugar control, risk was about 50 percent higher for people with AIC levels between 7 and 9, and nearly doubled for people with levels above 9.

Similarly, risk of the abnormal heart rhythm increased with diabetes duration; for every additional year a person had been taking diabetes medications, their risk of atrial fibrillation increased by 3 percent.

Doctors who treat diabetic patients should be aware of their increased atrial fibrillation risk, Dublin said. She pointed out that the condition can be treated effectively, for example with blood-thinning drugs to reduce stroke risk.

And for patients whose symptoms are interfering with their quality of life, for example making them short of breath with exertion, "we can make them feel a lot better by slowing their heart down with commonly used and safe drugs," she added.

SOURCE: Journal of General Internal Medicine, online April 20, 2010.