VIENNA — Diabetes was a significant risk factor for atrial fibrillation among women but not men in an analysis of electronic medical records from a large HMO database.
The study also found that both the prevalence and the incidence of atrial fibrillation (AF) were more than 40% higher among patients with diabetes than in those without. After accounting for other risk factors, diabetes increased the risk for AF by 16%, Gregory A. Nichols, Ph.D., said in an interview held prior to his scheduled presentation of the findings at the annual meeting of the European Association for the Study of Diabetes.
Although diabetes was previously known to be a risk factor for AF, this analysis is the first to assess its independent contribution by controlling for factors common to both conditions, and also the first to identify a strong sex difference in the relationship between the two conditions, said Dr. Nichols, a researcher at Kaiser Permanente Center for Health Research, Portland, Ore.
“Clinicians may be disincentivized to look for atrial fibrillation in women because it is such a male-dominated condition, but when diabetes is present in women the risk for atrial fibrillation is the same as it is for a man,” Dr. Nichols said in the interview.
Data were analyzed for 10,213 individuals who were members of the Kaiser Permanente Northwest diabetes registry as of Jan. 1, 1999, and another 7,159 patients who entered the registry by Dec. 31, 2004, for a total of 17,372. The index date was defined as Jan. 1, 1999, or date of registry entry, and each member with diabetes was matched with another member of the same age and sex without diabetes (Diabetes Care 2009;32:1851-6).
The subjects had a mean age of 58 years, and 51% were male. As expected, those with diabetes had higher body mass indexes and had higher blood pressures. They were also significantly more likely to have a history of stroke, hypertension, and heart failure.
At baseline, the prevalence of AF was 3.6% among those with diabetes versus 2.5% among those without, a significant 44% difference. The difference was most significant in the 55- to 64-year age group, with 3.0% of the diabetic patients versus 1.6% of the nondiabetic patients found to have AF, an 87% difference. The difference in AF prevalence between the diabetic and nondiabetic groups became smaller in the older age groups, he said.
Men had an overall greater prevalence of AF than did women, but the difference between the diabetic and nondiabetic groups was far greater in the women. In the 55- to 64-year age group, 2.2% of the nondiabetic versus 3.3% of the diabetic men had AF, a 50% difference. For the women, 1.0% versus 2.7% had AF, a 170% difference, said Dr. Nichols, who launched the Diabetes Registry at Kaiser Permanente Northwest in 1989.
The incidence analysis compared 16,057 diabetes patients who did not have AF at baseline with 16,471 without diabetes or AF at baseline. Over a mean follow-up of 7.2 years, the diabetic patients developed AF at an age/sex–adjusted incidence rate of 9.1/1,000 person-years, compared with 6.6/1,000 person-years in the nondiabetic patients.
For the men, AF incidence per 1,000 person-years was 10.8 for those with diabetes and 8.3 for those without the condition, a 31% difference. For the women, those figures were 7.6 versus 5.0, a difference of 46%. “Thus, women with diabetes have almost an identical incidence of AF as men without diabetes at 7 years. In women, diabetes removes the protective effect of female gender with regard to AF,” he said.
After controlling for age, sex, race, body mass index, systolic blood pressure, cigarette smoking, and comorbidities including ischemic heart disease, stroke, valvular disease, hypertension, and heart failure, diabetes still increased the AF risk by 16% overall.
But in men the increase was a nonsignificant 9%, compared with a highly significant 26% in women. The risk from being both female and having diabetes was larger than the overall increased risk conferred by either body mass index greater than 30 kg/m2 (22% increased risk) or by a systolic blood pressure greater than 140 mm Hg (24% increased risk), Dr. Nichols noted during the interview.
“Although women are at a lesser absolute risk of AF than men, diabetes imparts a greater relative risk of AF among women than men. A potential mechanistic link between these two important disease conditions, and the differential effects of gender, warrants further investigation,” he said.
Dr. Nichols stated that he had no relevant financial disclosures.
FULL TEXT