Analysis of Danish health records finds significant positive associations among the risk of stroke, the benefit of anticoagulation and the duration of disease in diabetics who develop atrial fibrillation (AF).
Researchers hoped to refine treatment guidelines — which currently advocate anticoagulation for nearly all diabetics with AF — by checking whether time spent with diabetes predicted a patient’s risk of thromboembolism or anticoagulant-related bleeding.
They gathered records for all 137,222 patients who were diagnosed with AF at Danish hospitals between 2000 and 2011 and determined that 12.4% of them had preexisting diabetes. After adjusting for anticoagulant use as well as congestive heart failure, hypertension, age, previous stroke, vascular disease, and sex, the researchers compared outcomes in non-diabetic AF patients with outcomes in those who had been diabetic for less than 5 years, those who had been diabetic for 5 to 9 years, those who had been diabetic for 10 to 14 years and those who had been diabetic for 15 years or more.
Patients from all of the diabetic groups were more likely than their non-diabetic peers to suffer a thromboembolism during the study period, but the risk grew steadily with disease duration. The mean risk elevation was only 11% (95% confidence interval [CI], 1.03-1.20) among patients who had been living with diabetes for less than 5 years but it was 48% (95% CI, 1.29-1.70) among those who had been living with diabetes 15 years.
When researchers looked for associations between disease duration and anticoagulant-related bleeding, however, they found nothing. Long-term diabetics who used anticoagulants to reduce AF stroke risk were no more or less prone to major bleeds than newly diagnosed patients.
“When analyzed as a continuous variable, duration of diabetes mellitus was associated with risk of thromboembolism in a dose-response-dependent manner, but not with a higher risk of bleeding during anticoagulant treatment,” the study authors wrote in Stroke. “Considering the critical balance between preventing thromboembolism and avoiding bleeding, longer duration of diabetes mellitus may favor initiation of anticoagulant therapy.”
Diabetics are significantly more prone than other people to develop AF. Just last year, a study team used 16 years’ worth of Danish records to trace the development of AF in all 5.2 million adult Danes who did not have the condition in 1996. Those records showed that 5.6% of all diabetics, but only 3.3% of all other people, developed AF by 2012.
The association may only exist through common risk factors such as obesity and age, but a number of large studies indicate a deeper connection. In the early 1990s, for example, the Framingham study found diabetes to be an independent risk factor for AF (odds ratio, 1.4 for men and 1.6 for women) after 38 years follow-up. An analysis of 41,436 Japanese patients from 2008, moreover, found the prevalence of diabetes was much greater in AF patients (20%) than in controls (12%).
Current guidelines from the American Heart Association (AHA)/American College of Cardiology/Heart Rhythm Society urge the use of anticoagulants in all AF patients who score 2 or higher on the CHA2DS2-VASc scale, which uses 7 factors to evaluate risk: Congestive heart failure, Hypertension, Age 75+, Diabetes mellitus, Stroke or TIA or thromboembolism, Vascular disease and Sex.