Endurance Training and Atrial Fibrillation: Sex Matters

A recent investigation in Sweden looking at atrial fibrillation (AF) in endurance athletes found that female cross country skiers were less susceptible to AF compared to male athletes while risk for stroke was lower in both male and female skiers even if they did develop AF, when compared to nonskiers with AF.

The findings were published online August 26, 2019, ahead of print in Circulation.

“This study suggests that although the fastest skiers had a comparable risk of atrial fibrillation to nonskiers, the stroke risk and mortality were lower after diagnosis of atrial fibrillation, suggesting that a lifestyle associated with highly competitive endurance sport is favorable,” wrote the researchers, led by Niclas Svedberg, MD of Falun Hospital, Falun, Sweden.

"...although the fastest skiers had a comparable risk of atrial fibrillation to nonskiers, the stroke risk and mortality were lower after diagnosis of atrial fibrillation, suggesting that a lifestyle associated with highly competitive endurance sport is favorable."

It is well established that high levels of exercise are associated with positive health effects. Athletes tend to have better glucose regulation, lower blood pressure, better lipid profiles, and lower mortality than more sedentary individuals. And yet there are also studies that link high levels of endurance training to a higher risk of AF. AF is a known risk factor for stroke while exercise typically lowers that risk.

Thus, Svedberg and colleagues designed their reserach to explore the relationship of endurance training to risk of AF and stroke as well as tease out potential gender differences in the association within this highly trained cohort.

Next: Study cohort, results

The study cohort comprised all Swedish skiers completing one or more cross-country races of moderate to extreme length (n=205 654) compared to a matched sample of nonskiers from the general population. The groups were followed until first event of AF or stroke.

Results

Female skiers had a lower rate of AF than female nonskiers independent of the number of races they were in or their finishing times while male skiers had a rate of AF on par with nonskiing men.

The incidence of AF was higher among skiers who skied more races with the fastest times. However, skiers with AF had a lower incidence of stroke and mortality compared to nonskiers with atrial fibrillation. Skiers with AF had a higher incidence of stroke than did skiers and nonskiers without AF. Male and female endurance athletes with AF had a 27% lower risk of stroke and 43% lower risk of dying than those in the general population with AF.

Male and female endurance athletes with AF had a 27% lower risk of stroke and 43% lower risk of dying than those in the general population with AF.

Final thougts, take home points

• Female endurance athletes appear to be less susceptible to AF than their male counterparts.

• While highly trained men do have a higher incidence of AF than less well trained men, the incidence is on par with the general population and it is not related to higher risk of stroke.

• The results suggest both male and female endurance athletes have a lower risk for stroke than the general population-a finding consistent with previous evidence supporting exercise as cardioprotective.

• The lower risk for stroke in endurance athletes with AF when compared to those in the general population with AF underscores the positive effects of exercise on other risk factors for stroke.

• Finally, the authors assert, based on these data, that AF in endurance athletes should be treated based on established clinical guidelines.
  
  Source: Svedberg N, Sundstrom J, James S, et al. Long-term incidence of atrial fibrillation and stroke among cross-country skiiers: cohort study of endurance trained male and female athletes. Circulation. 2019;140:00–00. DOI: 10.1161/CIRCULATIONAHA.118.039461