A study of 21,758 men, average age 51.7 years, followed for an average 10.4 years, showed that men who exercised the most have more plaques in their arteries, but do not suffer more heart attacks or deaths than those with less heart artery calcification (JAMA Cardiol, Jan 30, 2019). The least active men with excessive arterial plaques were twice as likely to die of heart disease. Compared to low-level exercisers, the heavy exercisers without increased plaques had half the risk of dying during the study period. This agrees with other studies showing that older athletes may have increased plaques in the arteries leading to their hearts (Circulation, 2017;136(2):138-148), even though they are at significantly reduced risk for suffering heart attacks and death from heart attacks (Prog Cardiovasc Dis, 2015;57(4):324-329). The studies have not shown whether exercise causes plaque formation or is just associated with it.
The CARDIA study, on 5,115 people who have been followed for more than 30 years so far, has shown that men who spend a lot of time exercising each week have more plaques than moderate exercisers, but do not suffer increased risk for heart disease (Mayo Clinic Proceedings, Oct 16, 2017). All of the recent studies showing increased plaques in older athletes showed that, compared to non-athletes, the athletes had stable plaques that are far less likely to break off to cause heart attacks (Circulation, 2017;136(2):149-151). Heavy exercisers live longer, and suffer far fewer heart attacks, than people who do not exercise (JAMA Intern Med, 2015; 175: 959–967; Circulation, 2007;116(9):1094-1105), and lack of exercise shortens lives and is associated with many different diseases (Lancet, 2012; 380: 219–229).
Heart Attacks Are Caused by Plaques Breaking off from Coronary Arteries
A heart attack has little to do with the size of plaques blocking arteries. A heart artery that is 90 percent blocked does not cause a heart attack. A heart attack is caused by a sudden complete blockage of blood flow to the heart muscle. First a plaque breaks off from the inner lining of an artery leading to the heart, followed by bleeding and clotting. Then the clot extends to block all flow of blood through that artery, which deprives the heart muscle of oxygen and the heart muscle dies.
Why People Who Exercise Extensively May Have More Plaques
Competitive older endurance athletes may have more plaques in their arteries than non-exercisers, but they often have the type of plaques that are far less likely to break off to cause heart attacks (Circulation, April 27, 2017;136:138-148; May 2, 2017;136:126-137). A possible explanation would be that plaques form in arteries from an unhealthful diet or undesirable genes, or both. Exercise does not prevent plaques from forming, but it can stabilize plaques so that they are less likely to break off to cause heart attacks. Since exercise burns lots of extra calories, it can make you eat more food. The studies do not tell us what these older athletes eat, but if you choose to eat more unhealthful foods (red meat, processed meats, sugared foods and drinks, fried foods and so forth), you can expect to have more plaques in your arteries (Journal of the American College of Cardiology, July 2017;70(4)). A heart-attack-preventing diet should be high in vegetables, whole grains, beans, nuts and other seeds. You also should avoid being overweight, restrict alcohol and not smoke.
However, people who spend a lot of time exercising have far more stable plaques. More stable plaques can explain why endurance athletes have such a low rate of heart attacks, and why increasing endurance training increases protection from heart attacks. Having stable plaques, and larger arteries that widen more, helps to prevent heart attacks. Exercisers have:
• lower 10-year-history risk scores for likelihood to suffer heart attacks (Framingham study, Prev Med, 2005;41:622–8)
• greater plaque thickness
• more calcium and less fat in their plaques
• more stable plaques that are far less likely to break off to cause heart attacks. By comparison, more than 60 percent of the older men who do not exercise regularly have soft plaques with a much higher risk for breaking off to cause heart attacks (Circulation, April 27, 2017;136:138-148 and May 2, 2017;136:126-137).
Diagnosing Stable or Unstable Plaques
An X-ray test called "calcium score" is used to measure the size of plaques in the arteries leading to the heart. This test can also tell whether the plaques are stable or unstable (American Journal of Roentgenology, March 2015;204(3):W249-W260). Many radiologists fail to report whether the plaques are stable and safe, or unstable and more likely to break off to cause a heart attack. A stable plaque is called "hard," has a thick calcium periphery to keep the plaque in place, and is not full of fat. An unstable plaque is "soft," has irregular calcium borders that may not hold the plaque in place, and is full of fat. If your calcium score results do not contain this information, ask your doctor to request it from the radiologist.
Preventing heart attacks requires both eating healthfully and exercising. Since exercise stabilizes plaques to help keep them from breaking off from arteries, exercise should be part of any heart-attack-prevention program.
Dedicated exercisers who need to eat large amounts of food to meet their caloric needs should choose healthful, anti-inflammatory foods to avoid forming more plaques in their arteries. Check with your doctor if you have evidence of heart disease caused by a faulty diet: high blood pressure, high blood cholesterol, high triglycerides, high blood sugar, high CRP (c-reactive protein, a measure of inflammation), an abnormal EKG, or chest pain, particularly with exercise.