SEATTLE, WASHINGTON. Diabetes (type 2) is associated with systemic inflammation (high CRP level), left atrial enlargement, obstructive sleep apnea, obesity, and alterations to autonomic nervous system function in the atria. As these conditions are recognized risk factors for atrial fibrillation (AF), it makes sense to ask the question, Are diabetics at increased risk of developing AF?

A group of researchers at the University of Washington recently set out to answer this question. Their study involved 1410 patients with newly diagnosed AF and 2203 controls without AF. Type of AF was classified as follows:

• Transitory – an episode lasting 7 days or less with no further episodes during the 6 months following diagnosis.
• Persistent/intermittent – an episode lasting longer than 7 days or recurring self-terminating episodes during the 6 months following diagnosis.
• Sustained – an episode lasting at least 6 months with no evidence of normal sinus rhythm.

The average age of AF patients was 74 years vs. 68 years for controls. Sixty-five percent of AF patients were female vs. 55% in the control group. Hypertension was common in both groups (75%) as was obesity (42%). AF patients were more likely to have heart disease or heart failure than were those in the control group. Of the 1410 cases with AF, 39% had the transitory variety, 45% the persistent/intermittent kind, and 15% sustained.

After adjusting for all potential confounders the researchers conclude that patients with treated diabetes have a 45% increased risk of developing AF when compared to a matched group of non-diabetics. There was no correlation between AF risk and untreated diabetes. The risk increased with years of pharmacologic treatment with patients having undergone treatment for more than 10 years having a 64% increased risk of AF. A higher value for glycosylated hemoglobin (HbA1c), a measure of longer-term glucose exposure, was also associated with increased AF risk. An HbA1c value between 8 and 9 was associated with a 46% increased risk, while a value above 9 was associated with a 96% increased risk.

The authors conclude that treated diabetics who have been on diabetes medications for more than 5 years or have an HbA1c value above 7 are at increased risk for developing AF. They caution that their findings may apply only to obese patients. They also suggest that the reason why untreated diabetics do not have an increased risk of AF is because they are probably earlier in the course of the disease or have milder disease.

Dublin, S, et al. Diabetes mellitus, glycemic control, and risk of atrial fibrillation. Journal of General Internal Medicine, Vol. 25, August 2010, pp. 853-58

Editor's comment: It seems to me the finding that patients undergoing pharmacologic treatment for diabetes have an increased risk of AF could equally well point to the possibility that common diabetes medications increase the risk of developing AF. Particularly in view of the finding that untreated diabetics do not have an increased risk of AF. In any case, the findings of this study are unlikely to be relevant to lone afibbers. An early LAF Survey involving 200 lone afibbers found that only 1% had diabetes, while 25% had hypoglycemia – once again substantiating the conclusion that heart disease-related AF is an entirely different entity than lone AF[1].
[1] Chambers, PW. Lone atrial fibrillation: Pathologic or not? Medical Hypotheses, Vol. 68, No. 2, 2007, pp. 281-87