Atrial fibrillation is associated with different levels of physical activity levels at different ages in men

Drca N, Wolk A, Jensen-Urstad M, et al.
Heart 2014 May 14. doi:10.1136/heartjnl-2013-305304

A reverse J-shaped association of leisure time physical activity with prognosis in patients with stable coronary heart disease: evidence from a large cohort with repeated measurements

Mons U, Hahmann H, Brenner H
Heart 2014 May. doi:10.1136/heartjnl-2013-305242
 Physical activity is inversely associated with the risk of developing cardiovascular disease in healthy adults [1]. Numerous clinical trials show that exercise-based cardiac rehabilitation improves prognosis in heart disease patients [2,3].
Patients with cardiovascular risk factors or heart disease are usually encouraged to engage in regular physical activity, to reduce the burden of CV disease.
For most health outcomes, additional benefits occur as the amount of physical activity increases through higher intensity, greater frequency, and/or longer duration [4]. However, increasing evidence supports the hypothesis that regular exercise increases the risk of atrial fibrillation (AF), ventricular arrhythmias or even ischaemic heart disease [5]. A dose-response relationship between physical activity and cardiovascular disease is still unclear.
Two recently published papers explored this subject.

Exercise & AF

The study by Drca et al. examined the influence of physical activity at different ages and of different types, on the risk of developing AF in a large cohort of Swedish men.
Information about physical activity was obtained from 44,410 atrial fibrillation (AF)-free men, aged 45–79 years (mean age=60), who completed a self-administered questionnaire at baseline in 1997. The questionnaire included information on leisure-time exercise and on walking or bicycling throughout their lifetime (at 15, 30 and 50 years of age, and at baseline).
The study participants were followed for a median of 12 years, during which time 4,568 cases of AF were diagnosed.

Main outcomes:

• Men who reported exercising more than 5 hours a week at the age of 30 had a relative risk of developing atrial fibrillation of 1.19 (95% CI 1.05-1.36) compared with those who reported exercising less than 1 hour a week at the same age.
• The risk was higher (RR 1.49, 95% CI 1.14-1.95) among the men who exercised >5 h/week at age 30 and quit exercising later in life (<1 h/week at baseline).
• Walking/bicycling at baseline was inversely associated with risk of AF (RR 0.87, 95% CI 0.77-0.97 for >1 h/day versus almost never) and the association was similar after excluding men with previous coronary heart disease or heart failure at baseline (corresponding RR 0.88, 95% CI 0.77-0.998).

Conclusions

Intense physical activity, like leisure-time exercise of more than 5 h/week at the age of 30 years,
increased the risk of developing atrial fibrillation later in life. By contrast, moderate-intensity physical activities, like walking or bicycling of more than 1 h/day later in life at older age decreased the risk

Exercise & CHD

The study by Mons et al. tried to establish the dose-response relationship associated with different levels of physical activity in patients with stable heart disease followed for a decade.
Subjects included a prospective cohort of 1,038 patients in Germany with stable CHD participating in the KAROLA study.
The frequency of strenuous leisure time physical activity was assessed repeatedly over 10 years of follow-up and the association of physical activity level with different outcomes of prognosis was determined (major cardiovascular events, cardiovascular mortality, all-cause mortality).

Main outcomes:

• For all outcomes, the highest hazards were consistently found in the least active patient group, with a roughly twofold risk for major cardiovascular events (adjusted model 2.05 [95% CI 1.20-3.51]) and a roughly fourfold risk for all-cause mortality (3.92 [95% CI 2.26-6.79]) in comparison to the reference group of patients who were moderately active (exercised two- to four-times per week).
• When taking time-dependence of physical activity into account, the data indicated reverse J-shaped associations of physical activity level with cardiovascular mortality, with the most frequently active patients also having increased hazards (2.36, 95% CI 1.05 to 5.34).

Conclusions

As expected, the highest hazards for adverse outcomes were found in the least active patient group.
However, substantially increased hazards were also observed in the most frequently physically active groups, indicating reverse J-shaped associations of physical activity level with cardiovascular mortality.

Editorial comments [6]

With respect to AF, other studies have found a similar association between intense exercise at an early age and the later development of AF. Exercise that is self-reported to be intense is likely more intense in 30-year-olds than in 60-year-olds.
With respect to CHD, intensive exercise may have a pro-inflammatory effect that may be especially harmful in some people with atherosclerotic disease.
The ability of both studies to reliably assess the impact of physical activity on outcomes was limited because they were both based on self-administered questionnaires in which study participants were asked to recall their physical activity years and even decades earlier and were not asked to provide specific information about the exercise they engaged in.
In summary, the two studies suggest that for exercise maximum cardiovascular benefits are obtained if performed at moderate doses, while these benefits are lost with (very) high-intensity and prolonged efforts.

References

1. Li J, Siegrist J. Physical activity and risk of cardiovascular disease—a meta-analysis of prospective cohort studies. Int J Environ Res Public Health 2012;9:391–407 2. Heran BS, Chen JM, Ebrahim S, et al. Exercise-based cardiac rehabilitation for coronary heart disease. Cochrane Database Syst Rev 2011:CD001800.
3. Lawler PR, Filion KB, Eisenberg MJ. Efficacy of exercise-based cardiac rehabilitation post-myocardial infarction: a systematic review and meta-analysis of randomized controlled trials. Am Heart J 2011;162:571–84, e2.
4. Eckel RH, Jakicic JM, Ard JD, et al. 2013 AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2013. doi:10.1161/01.cir.0000437740.48606.d1
5. Guasch E, Nattel S. CrossTalk proposal: Prolonged intense exercise training does lead to myocardial damage. J Physiol 2013;591(Pt 20):4939–41.
6. Guasch E, Mont L. Exercise and the heart: unmasking Mr Hyde. Heart. 2014 May 14. pii: heartjnl-2014-305780. doi: 10.1136/heartjnl-2014-305780.