Older Men With Existing Coronary Disease at Highest Risk of Dying During a Triathlon

CHICAGO, IL—Over a recent 30-year period, a little more than one hundred men and women have died participating in triathlons in the United States, with the risk higher in men, particularly middle-aged men, according to the results of a new analysis. The vast majority of these deaths occurred in the swimming portion of the event, say researchers.

Kevin Harris, MD (Minneapolis Heart Institute Foundation, Minneapolis), who presented at the American College of Cardiology 2016 Scientific Sessions earlier this week, said there are 1.5 deaths per 100,000 participants overall. For men and women, there are 2.05 and 0.71 deaths per 100,000 participants, respectively. Individuals who died while participating were older than the rest of the field, with average ages of 50 and 38 years, respectively.

“Overall, it’s a pretty small number, but it’s not a small number to the families,” Harris told TCTMD. “I think from this analysis we are starting to discern individuals who might be at greater risk. They’re men, primarily, a little older, and they often have coronary disease. So, I think one of the messages would be—there’s a lot of men that don’t see their doctors—if you’re thinking about doing a triathlon, and you haven’t been to a doctor, and you’re at cardiovascular risk, this would definitely be the time to get checked out.”

The latest analysis—spanning three decades of races sanctioned by USA Triathlon—grew out of an earlier study the group conducted. In that analysis, which only included triathlons from 2006 to 2008, there were 14 deaths among 922,810 participants.

Still interested in the topic, the group decided to conduct an expanded analysis to study the risk of death over a wider time frame. In the United States, membership with USA Triathlon—the sport’s governing body—grew by more than 250% from 1999 to 2014.

Between 1985 and 2015, there were 109 individuals who died participating in a triathlon, with 76 of these participants dying during the swim and 19 while cycling, although nearly 75% of deaths during the bike portion of the race were the result of trauma caused by collision. The remainder of deaths occurred on the run or immediately after the race. There were 46 autopsies performed, and nearly half of the deceased had definite cardiovascular abnormalities. Harris said 16 patients had significant coronary lesions while three patients had hypertrophic or dilated cardiomyopathy.

“We don’t really have a lot of clinical information about what was going on with the athlete beforehand,” said Harris. He suspects that during a stressful race, with increased adrenaline and heart rates, there would be diminished flow to the heart in individuals with atherosclerotic coronary disease, which could lead to an arrhythmia. “We can’t rule out they were kicked, or were taking on water,” he said. “It’s hard to distinguish [the exact cause of death].”

Interestingly, 52% of the deaths occurred in “short” triathlon races, which was defined as a race with a swim segment less than 750 meters. Slightly more individuals died during medium-length races (27%) than in long races where the swim segment was longer than 1500 meters (21%), such as Olympic-distance, half-Ironman, and Ironman races. Over the 30-year period, there were 12 resuscitated cardiac arrests, including in 5 individuals who were swimming when the arrest occurred.

By way of comparison, Harris noted that a 2012 study by Jonathan Kim, MD (Massachusetts General Hospital, Boston, MA), and Aaron Baggish, MD (Brigham and Women’s Hospital, Boston, MA), showed the incidence of cardiac arrest and sudden cardiac death among 10.9 million marathon runners was approximately 1 per 184,000 and 259,000 participants, respectively.

Many individuals have been doing triathlons for a number of years and have little or no cardiovascular risk factors, Harris noted. However, if he sees a patient who is thinking about a triathlon and they have the higher-risk profile—male, older, some degree of cardiovascular risk—he would consider cardiovascular screening, although what test he’d use remains an open question. Stress echocardiography would identify hypertrophy and give an indication of ischemia, while others might consider a coronary artery calcium scan, he said.

How Much Is Too Much Exercise?   

In a session devoted to lifestyle medicine at the ACC scientific sessions—one entitled “A Little Less Drug, a Little More Sex, and a Lot More Rock and Roll”—Peter McCullough, MD (Baylor University Medical Center, Dallas, TX), addressed the question of “dose” when it comes to exercise. Specifically, McCullough highlighted an ongoing debate within the United States, as well as internationally, about whether it’s possible to get too much of a good thing when it comes to exercise.

“The notion that we could take something that was healthy and go too far has been really brought to the fore, that it could be hazardous beyond things like orthopedic injuries and dehydration,” said McCullough. “But we need to know that the vast majority of individuals who have a sudden death or cardiac event during an athletic event do so because of things like myocardial ischemia, structural heart disease, or inherited channelopathies. These account for about 60% of the cases you see in the newspaper.”

To explain the remaining 40% of deaths, research has turned to possible adverse cardiovascular changes resulting from endurance sports. For example, studies of marathon runners have highlighted a nonischemic rise in cardiac troponin levels immediately after the race, which McCullough suggests might be the result of volume overload in the right ventricle and atrium. He also noted that “there is an explosion of peptides” when measured before and after long-distance endurance sports, while they have documented an eight-fold increase in C-reactive protein over the course of a marathon.

“We found there is a whole variety of candidate proteins that upregulate throughout the course of a marathon and this really leads to the idea that maybe these chronic changes over and over again might actually be promoting cardiac fibrosis,” said McCullough, referring to cumulative effects of long-distance endurance sports.

He noted many observational studies have shown that longtime marathon runners do develop patches of myocardial fibrosis, and these disappear when exercise intensity and duration is reduced. He said there doesn’t appear to be much doubt about the “U-shaped association” between exercise intensity and atrial fibrillation either.

The bottom line is that it takes “a lot to go too far with exercise,” but there does appear to be a “hazard zone” with volume and intensity, said McCullough. The current recommendations—moderate-intensity aerobic exercise for 30 minutes per day at least 5 days per week—is reasonable for the vast majority of population.

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