Cardiorespiratory Fitness and Risk of Incident Atrial Fibrillation: Results from the Henry Ford ExercIse Tesing (FIT) Project
Background—Poor cardiorespiratory fitness (CRF) is an independent risk factor for cardiovascular morbidity and mortality. However, the relationship between CRF and atrial fibrillation (AF) is less clear. The aim of this analysis was to investigate the association between CRF and incident AF in a large multi-racial cohort that underwent graded exercise treadmill testing.
Methods and Results—From 1991-2009, a total of 64,561 adults (mean age: 54.5 ± 12.7 years, 46% female, 64% whites) without AF underwent exercise treadmill testing at a tertiary-care center. Baseline demographic and clinical variables were collected. Incident AF was ascertained using international classification of diseases code v. 9 (ICD-9 427.31) confirmed via linkage to medical claim files. Nested, multivariable Cox proportional hazards models were used to estimate the independent association of CRF with incident AF. During a median follow-up of 5.4 years (IQR 3-9 years), 4,616 new cases of AF were diagnosed. After adjusting for potential confounders, a 1 higher MET achieved during treadmill testing was associated with a 7% lower risk of incident AF [HR (95% CI): 0.93 (0.92 - 0.94) p < 0.001]. This relationship remained significant after adjustment for incident coronary artery disease [HR (95% CI): 0.92 (0.91 - 0.93) p < 0.001]. The magnitude of the inverse association between CRF and incident AF was greater among obese compared with non-obese (p-interaction=0.02) individuals.
Conclusions—There is a graded, inverse relationship between cardiorespiratory fitness and incident AF. This association was stronger for obese as compared with non-obese., especially among obese patients.
- Received December 12, 2014.
- Revision received March 2, 2015.
- Accepted March 19, 2015.