Atrial fibrillation occurs when the two upper chambers of the heart beat irregularly and too fast, causing blood to pool and clot. If the clot travels out of the heart and becomes lodged in an artery or in the brain, it can cause a stroke. About 2.2 million Americans are diagnosed with AF; however, many more people have the condition but don-t know it. Diabetes affects more than 23 million Americans-and, according to the study, nearly 4 percent, or 1 million, have atrial fibrillation.

The study involved 17,372 patients in Kaiser Permanente-s diabetes registry in Oregon and Washington and an equal number of non-diabetic patients, matched for age and sex. Researchers used Kaiser Permanente HealthConnect-, the world-s largest civilian electronic health records system, to identify the non-diabetic patients. The two groups were followed for an average of 7.2 years until Dec., 31, 2008, or until they died or left the health plan. At the start of the study 3.6 percent of the patients with diabetes had AF, vs. only 2.5 percent of the non-diabetic patients-a difference of 44 percent. During the study period, diabetics were more likely than non-diabetics to develop AF. But after controlling for other factors like obesity, high blood pressure and age, the increased risk was only significant among women. Women with diabetes were 26 percent more likely than their non-diabetic counterparts to develop AF.

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