Abstract 12962: Association of Cardiorespiratory Fitness and Body Mass Index in Midlife With Atrial Fibrillation in Later Life: the Cooper Center Longitudinal Study
Background: While it is well established that obesity is associated with an increased risk for atrial fibrillation (AF), the joint association between obesity, cardiorespiratory fitness (fitness), and AF is not known. Therefore, we sought to determine the association between fitness and body mass index (BMI) in middle age with AF in older age.
Methods: We included 18,140 (21.6% women, mean age 49 years) free of cardiovascular disease, cancer, chronic obstructive pulmonary disease, and diabetes at baseline enrolled in the Cooper Center Longitudinal Study (CCLS) between 1970 and 2009. Fitness was measured by Balke protocol and categorized according to treadmill time into low-fit (Quintile 1), intermediate-fit (Q2-3), and high-fit (Q4-5) categories. Other baseline risk factors were measured using standard protocols. Data from the CCLS were linked to Medicare administrative claims data from the Center for Medicare and Medicaid Services (CMS). The outcome was diagnosis of AF defined using validated algorithms from CMS. Cox proportional hazards models were used to estimate the association between midlife fitness and development of AF in older age, controlling for BMI and other factors.
Results: After 117,168 person years of Medicare follow-up time, the overall rate for AF was 19.2/1000 person years. The rates for high and low-fit were 18.0 and 21.5 respectively, and the rates for non-obese and obese were 18.6 and 24.6 respectively. In multivariable models, higher fitness was associated with a lower AF risk after age 65 [HR=0.86 (0.76-0.98), high fit vs. low fit]. When BMI was included in the model, higher BMI was associated with a higher risk for AF [HR 1.15 (1.10-1.20), per 3kg/m2]. However, the association between fitness and AF was no longer apparent.
Conclusion: The inverse association between fitness and AF risk can be explained by differences in obesity. These findings suggest the importance of favorable BMI in middle-age for the prevention of AF across the lifespan.
- © 2013 by American Heart Association, Inc.