Introduction:
Atrial fibrillation (AF) is the most common sustained arrhythmia, affecting >10 million in the USA. The beneficial effects of cardiorespiratory fitness (CRF) on cardiovascular (CV) diseases are well-documented. Interestingly, African American (AA) individuals are less prone to develop AF. Little is known about the association between CRF and AF in AA men.
Hypothesis:
CRF-AF risk association in AA men.
Methods:
We identified 11,216 AA Veterans with a mean age (±SD) 58±11 years who completed a symptom-limited exercise treadmill test at the VAMCs in Washington DC and Palo Alto CA. None exhibited evidence of ischemia or AF during and prior to it. We established four fitness groups based on age-specific quartiles of peak metabolic equivalents (METs) achieved: Least-Fit: 4.4 ±1.2 METs (n=2,530); Moderate-Fit: 6.6±1.3 METs (n=3,361); Fit: 8.1±1.4 METs (n=2,719) and High-Fit: 11.2±2.4 METs (n=2,606). AF was identified by a search of the medical records CPRS (database) using ICD coding and verified by 2 investigators. Cox proportional hazard models adjusted for age, CV disease, CV medications and risk factors were constructed to assess the CRF-AF association. P-values <0.05 using two sided tests were considered statistically significant.
Results:
During a mean follow-up period of 10.7±6.2 years, 1,423 patients developed AF; 421(16.6%) in the Least-Fit, 366 (10.9%) in Moderate-Fit, 323 (11.9%) in Fit and 313 (12%) in the High-Fit group. The CRF-AF association was inverse and graded. When compared to the patients in the Least-Fit group, the AF risk in the Moderate-Fit group was 29% lower (HR=0.71; 95% CI: 0.62-0.82, p<0.001). For Fit and High-Fit patients, the risk was 37% (HR=0.63; 95% CI: 0.54-0.73, p<0.001) and 51.0% lower (HR=0.49; 95% CI: 0.42-0.57, p<0.001), respectively.
Conclusion:
In this cohort, higher fitness levels reduced and delayed the risk of atrial fibrillation. The CRF-AF association was inverse, graded and independent of comorbidities.