Metabolic syndrome linked to higher rates of atrial fibrillation

February 25, 2008 By Benjamin A. Olenchock, M.D. Ph.D. [mailto:bolenchock@partners.org]

Niigata, Japan There have been a number of studies this year characterizing novel risk factors and predictors for the development of atrial fibrillation, most focusing on inflammatory markers and inflammatory conditions such as obesity. Additionally, the role of statins in protection against atrial fibrillation has received much attention. Now, researchers in Japan have studied the association between the metabolic syndrome – a constellation of heart disease risk factors – and atrial fibrillation.

This community-based study by the Niigata Association for Comprehensive Health Promotion and Research prospectively evaluated 28,449 patients over a mean period of 4.5 years through an annual health check-up program. The mean cohort age was 59.2+/-11.0 and 66% of the participants were women. At the onset of the study no participants had atrial fibrillation. Metabolic syndrome was defined based on criteria from two guidelines, the National Cholesterol Education Program Third Adult Treatment Panel (NCEP-ATPIII) and the American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI). According to these criteria, 3716 (13%) and 4544 (16%) participants, respectively, initially presented with metabolic syndrome.

Over the course of follow-up, atrial fibrillation developed in 265 subjects, 105 of which were women. Incidence of atrial fibrillation per 1000 person-years was 4.1 in men and 1.3 in women. Age and sex-adjusted incidence of atrial fibrillation was higher in those individuals with metabolic syndrome than those without (by NCEP-ATPIII definition HR 1.88, CI 1.4 to 2.52, p<0.001; by AHA/NHLBI definition HR 1.61, CI 1.21 to 2.15, p=0.001). The individual components of the metabolic syndrome were independently associated with risk of atrial fibrillation including obesity, high blood pressure, low HDL cholesterol, and impaired insulin tolerance, with obesity (HR 1.64) and high blood pressure (HR 1.69) associated with the greatest risks. The association between inflammation and risk of atrial fibrillation is becoming clearly established. This new study contributes support for this hypothesis, and additionally identifies patients with metabolic syndrome as having almost 2-fold higher rates of atrial fibrillation. The usefulness of the term metabolic syndrome is the identification of patients with a group of interrelated comorbidities that place them at increased risk for developing cardiovascular disease. The metabolic syndrome as a risk factor per se is of questionable utility, as the component risks clearly comprise the syndrome risk. Nonetheless, this work carefully characterized patients with metabolic syndrome by two commonly used definitions, and their findings bring attention to atrial fibrillation as yet another risk for patients with the metabolic syndrome.