If you're middle-aged or older and you work out, it's not too long before the question crosses your mind: I wonder if this could kill me?
It certainly has happened before. Jim Fixx, who helped start the fitness revolution with his book The Complete Book of Running, famously collapsed and died on a run at age 52. Young, highly conditioned basketball players Reggie Lewis and Hank Gathers died on the court of sudden cardiac problems. And everyone seems to know a story about someone who collapsed during a friendly soccer match or touch football game.
The high-profile deaths and personal anecdotes obscure the fact that numerous studies of marathoners and other athletes reveal just a small number of cardiac-related fatalities annually, and that many of the victims showed signs of undetected heart conditions.
"One thing we have learned," said Sumeet Chugh, associate director of the Heart Institute at Cedars-Sinai Medical Center in Los Angeles, "is it's not the exercise that's killing people. It's the heart condition."
Chugh and his colleagues decided to look at the issue a different way. Instead of studying athletes, they examined data on all the sudden cardiac arrests among 35- to 65-year-olds between 2002 and 2013 in the Portland, Ore. metropolitan area. The results, released Monday, showed that just 63 of 1,247 (5 percent) occurred during sports activity. Men were much more likely to suffer sudden cardiac arrest than women while taking part in sports, and the events were more likely to be seen by others. As a result, survival rates were somewhat higher.
"If you look at the overall burden of cardiac arrest in middle aged people . . . it turns out only 5 percent had it when they were doing some kind of sporting activity," Chugh said in an interview. "That is very good news and we really didn't know that before."
Sudden cardiac arrest is not the heart attack we typically think of - a blocked artery that cuts off the blood supply to the heart muscle. Many of those myocardial infarctions are survivable. Sudden cardiac arrest is "ventricular fibrillation," a disturbance of the electrical activity that governs the ordered, rhythmic pumping of the heart. The heart's lower chambers lose their synchronization and death occurs in 10 minutes unless someone who knows CPR or has a defibrillator intervenes quickly. About 95 of every 100 victims die, Chugh said.
The triggers of such events are not well known, but risk factors are. They include coronary artery disease, obesity, smoking, a thick-walled heart, a poor "ejection fraction" - the heart's ability to squeeze blood out to the rest of the body - and arterial plaque that can rupture, Chugh said.
His study, published in the journal Circulation, notes that sudden cardiac arrest accounts for nearly half of all cardiovascular-related deaths. The sports-related attacks occurred most often during jogging (27 percent), but also during basketball games (17 percent), while cycling (14 percent), at the gym (11 percent), and while playing golf (8 percent), volleyball, tennis or soccer (3 percent each). The average age at the time of the attack was 51. Surprisingly, 44 of the 63 showed some kind of symptoms that might have indicated heart problems in the week before the attack, including nine with chest pain, the study shows.
Even if someone nearby knows CPR or has a defibrillator, survival is unlikely. "The odds are against you but it depends on your luck " Chugh said. "A marathon is a good place. A basketball court may be."
For that reason Chugh said that even the hint of a symptom should be enough to discourage a middle-aged or older person from undertaking a rigorous bout of exercise until he knows whether he has a problem. "If you don't feel good, you shouldn't do it," he said. "If you have the flu, it's a bad idea."
But the small number of sports-related sudden cardiac arrests clearly indicates that the benefits of a regular, reasonable exercise program outweigh the risks of collapsing during such exertion, even for people with risk factors.
"The findings from this study should in no way discourage patients with cardiovascular risk factors from engaging in regular, appropriate physical exercise within a framework of simple guiding rules from the treating physician," the researchers wrote.