Extreme Exercise and Atrial Fibrillation

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Virtually all doctors agree that exercise helps to keep you healthy and to prolong your life. People who exercise into later life live longer than non-exercisers and are at reduced risk for high blood pressure, heart attacks, premature death, diabetes, strokes and even some cancers (Circulation, July 25, 2022;146(7):523–534). Endurance bicycle racers who participated in the Tour de France from 1947 to 2012 have lived an average of five years longer than their countrymen (European Heart Journal, 2013;34 (40):3145-3150). People who exercise regularly are far less likely to develop irregular heartbeats called atrial fibrillation (European Heart Journal, July 2021;42(25):2472–2483; Circulation, April 22, 2015). However:
• Competitive athletes appear to be almost two and half times more likely than non-athletes to experience atrial fibrillation (British Journal of Sports Medicine, Oct 2021;55(21):1233-1238).
• About 20 percent of almost 1000 long-term competitive endurance athletes, mostly middle-aged men, said they had been diagnosed with atrial fibrillation (Clinical Journal of Sport Medicine May 2023, 33(3):p 209-216).
• Long-term female competitive endurance athletes are at increased risk for atrial fibrillation (British Journal of Sports Medicine, 2023;57:1175-1179).
• Older endurance cross country skiers are at increased risk for atrial fibrillation (Circulation, Aug 26, 2019;140(11):910–920).
• Extreme endurance exercisers such as bicycle racers, cross country skiers and long-distance runners who compete into their 40s and beyond may be at increased risk for atrial fibrillation (American Journal of Cardiology, October 15, 2014;114(8):1229–1233).
• The incidence of atrial fibrillation appears to be more common in older athletes than in the general population (J Am Coll Cardiol, 2005;46:690–6).
• Articles in the Wall Street Journal, the New York Times and other popular media have suggested that some athletes who continue to do extensive fast mileage or train for extreme endurance events in later life may be increasing their risk for atrial fibrillation.

What is Atrial Fibrillation?
Each heartbeat starts when a “battery” in the upper heart (atrium) sends an electrical impulse through the upper heart to make it contract to squeeze blood toward the lower heart (ventricle). Then the electrical impulse reaches another “battery” in the lower heart to make the lower heart squeeze blood forward. Atrial fibrillation means that the upper heart quivers and does not push blood forward, while the lower heart beats independently. Many people with atrial fibrillation have no symptoms and do not know that they have this condition until it is discovered during a routine physical examination. Symptoms may include:
• Palpitations (a feeling that the heartbeat is racing, uncomfortable, or irregular)
• Muscle weakness
• Reduced ability to exercise
• Fatigue
• Lightheadedness
• Dizziness
• Confusion
• Shortness of breath
• Chest pain

These symptoms are often harmless, but on rare occasions an irregular heartbeat can cause sudden death by stopping the heart from pushing blood through your body or worse, can cause a clot to form in the upper heart that travels to another part of the body to block the flow of blood to that part of the body.

Atrial fibrillation is the most common irregular heartbeat. It occurs in 1.5-2 percent of the general population, and risk increases with age. It affects 10 percent of 75-year-olds and 20 percent of those over 85, because aging increases the risk factors for atrial fibrillation such as blocked arteries, high blood pressure or diabetes.

How Atrial Fibrillation Can Harm You
When a person has an upper (atrial) heart that is fluttering, blood pools there and a clot can collect and pass to the brain to cause a stroke, or to the lungs to block blood flow through the lungs. This is so dangerous that most doctors prescribe anti-clotting agents to everyone with atrial fibrillation. I believe that athletes with atrial fibrillation are far less likely to suffer clots that cause strokes than non-athletes with atrial fibrillation, but I have not seen any studies to support my belief. Healthy athletes can have occasional irregular heartbeats that will not harm them, but at this time, doctors treat atrial fibrillation in athletes the same way they treat other patients with this condition.

Extreme Exercise May Increase Atrial Fibrillation Risk
Two studies raised the concern about extreme amounts of exercise in older athletes. In the first study, 29 elite athletes were given MRIs to look for heart muscle scarring that increases risk of atrial fibrillation. They were Olympic or national team runners and rowers who had competed throughout their lives, including some who had competed in more than 100 marathons. In the older group of 12 athletes ages 50 to 67, half showed some heart muscle scarring (J Appl Physiol, June 2011;110(6):1622-6). Those who had trained the longest and hardest had the most scarring. Neither the 17 younger athletes (20-42) nor the control group of 20 older non-athletes showed this heart muscle scarring.

In the second study, on rats, a 16-week program of daily one-hour treadmill running caused widening of the upper part of their hearts and scarring in the heart muscle that could increase risk for irregular heartbeats (J Am Coll Cardiol, July 2013;62(1):68-77). The scars in the upper heart remained after the rats stopped exercising.

Risk Factors for Atrial Fibrillation
• High blood pressure is the most significant risk factor for atrial fibrillation (Hypertension, 2012 Feb;59(2):198-204). Blood pressures greater than 140/90 significantly increased risk (J Am Soc Hypertens, 2015 Mar;9(3):191-6).
• Diabetes. High blood sugar levels can damage heart muscle itself (Cardiovascular Diabetology, Jan 18, 2020;19(9)).
• Overweight (J Am Coll Cardiol, Jul 7, 2015). A program getting people to reduce their excess body weight markedly reduced symptoms in patients who already had atrial fibrillation (JAMA, 2013;310(19):2050-206).
• Alcohol.
• Smoking.
• An over-active thyroid.
• A very low heart rate, below 50 beats per minute (Circ Arrhythm Electrophysiol, 2013, Aug;6(4):726-31).
• Abnormal coronary artery calcium score, even with no heart symptoms (Am J Cardiol, 2014 Dec 1;114(11):1707-12). This test for plaques in heart arteries can be ordered by any doctor.
• Lack of exercise. Exercise helps to prevent atrial fibrillation; fit men had a 23 percent lower susceptibility for atrial fibrillation (Am J Cardiol, 2012 Aug 1;110(3):425-32).
• Aging. The older you are, the more likely you are to suffer atrial fibrillation. Walking or cycling is associated with a decreased risk in older people (Heart, 2014 Jul;100(13):1037-42).
• Possibly extreme ultra-endurance exercise.

My Recommendations
Exercise reduces the chances of a person developing atrial fibrillation. Nobody has shown that exercise in itself causes atrial fibrillation, and it is only extreme ultra-endurance exercise that some doctors believe may increase risk for atrial fibrillation. I think that nutrition, exposure to pollutants and other lifestyle factors are also important. I do not believe that just exercising will give you adequate protection from heart disease. To protect your heart, you should follow all of the rules that apply to everyone whether you compete in ultra-endurance events, exercise moderately or just sit on a couch.
• eat lots of fruits and vegetables
• severely restrict sugar-added foods and drinks
• restrict red meat and fried foods
• avoid smoking, second-hand smoke and third-hand smoke
• restrict alcohol
• avoid overweight
• exercise

The scientific literature recommends exercise for most people, but prolonged exercise through pain and exhaustion may increase risk for atrial fibrillation. If you have, or suspect that you may have, atrial fibrillation or any heart disease, always check with your doctor first about exercising. Never ignore symptoms that could be caused by heart disease, such as:
• sudden heart palpitations
• unexplained shortness of breath
• a drop in exercise performance
• chest pain