Reduced incidence of cardiac arrhythmias in walkers and runners

Abstract

Purpose: Walking is purported to reduce the risk of atrial fibrillation by 48%, whereas jogging is purported to increase its risk by 53%, suggesting a strong anti-arrhythmic benefit of walking over running. The purpose of these analyses is to compare incident self-reported physician-diagnosed cardiac arrhythmia to baseline energy expenditure (metabolic equivalent hours per day, METhr/d) from walking, running and other exercise.

Methods: Proportional hazards analysis of 14,734 walkers and 32,073 runners.

Results: There were 1,060 incident cardiac arrhythmias (412 walkers, 648 runners) during 6.2 years of follow-up. The risk for incident cardiac arrhythmias declined 4.4% per baseline METhr/d walked by the walkers, or running in the runners (P = 0.0001). Specifically, the risk declined 14.2% (hazard ratio: 0.858) for 1.8 to 3.6 METhr/d, 26.5% for 3.6 to 5.4 METhr/d, and 31.7% for ≥5.4 METhr/d, relative to <1.8 METhr/d. The risk reduction per METhr/d was significantly greater for walking than running (P<0.01), but only because walkers were at 34% greater risk than runners who fell below contemporary physical activity guideline recommendations; otherwise the walkers and runners had similar risks for cardiac arrhythmias. Cardiac arrhythmias were unrelated to walking and running intensity, and unrelated to marathon participation and performance.

Conclusions: The risk for cardiac arrhythmias was similar in walkers and runners who expended comparable METhr/d during structured exercise. We found no significant risk increase for self-reported cardiac arrhythmias associated with running distance, exercise intensity, or marathon participation. Rhythm abnormalities were based on self-report, precluding definitive categorization of the nature of the rhythm disturbance. However, even if the runners' arrhythmias include sinus bradycardia due to running itself, there was no increase in arrhythmias with greater running distance.

Figure 1. Reduction in the risks for incident cardiac arrhythmias per METhr/d for walking and running energy expenditure combined relative to the least active walkers and runners.

Adjustment for BMI and hypertension treatment had little effect on these risk reductions. Energy expenditure (X-axis) is categorized in terms of the upper limit of the minimum recommended physical activity levels (750 MET⋅min/wk = 1.8 METhr/d [10], [18]), e.g., 1 to 2-fold higher activity covers from 1.8 to 3.6 METhr/d, 2- to 3-fold covers from 1.6 to 3.4 METhr/d etc. Error bars represent 95% confidence intervals. Significant levels relative to <1.8 METhr/d coded: * P<0.05; † P<0.01, ‡ P<0.001, and ‡ P<0.0001. The superscript § means that the risk for runners who ran ≥3-fold was significantly less than those who ran <1-fold the recommended level.

Figure 2. Reduction in the risks for incident cardiac arrhythmias per METhr/d energy expended by walking and running separately relative to the least active walkers.

Energy expenditure (X-axis) is categorized in terms of the upper limit of the minimum recommended physical activity levels (750 MET⋅min/wk = 1.8 METhr/d [10], [18]), e.g., 1 to 2-fold higher activity covers from 1.8 to 3.6 METhr/d, etc. Error bars represent 95% confidence intervals. Significant levels relative to the least active walkers coded: * P<0.05; † P<0.01, and ‡ P<0.0001. The superscript § means that the risk for runners who ran ≥3-fold was significantly less than those who ran <1-fold the recommended level (P<0.05).