Triathlon competitors may be more likely to die suddenly and suffer a fatal trauma or cardiac arrest than previously thought, new data suggest.
A study of more than nine million participants over three decades found that deaths and cardiac arrests struck 1.74 out of every 100,000 competitors.
Until now, researchers thought it would be roughly the same as the risk for marathon runners, which is roughly half that rate.
The majority of triathlon deaths were recorded during the swimming section, which is the first round.
But despite gleaning that detail, the researchers from Minnesota admitted they were baffled by the extremely high mortality risk.
Triathlon deaths after 1.74 per 100,000 competitors – double the rate of marathon runners
‘The majority of deaths occur in the swim portion of the triathlon, which is the first portion of the race,’ said lead study author Dr. Kevin Harris, a cardiologist at Minneapolis Heart Institute Foundation at Abbott-Northwestern hospital in Minnesota.
‘During this portion of the race, the athletes likely experience an adrenaline surge as they enter the water and are competing in close proximity to other athletes, and in some cases with environmental conditions that are difficult to prepare for,’ Harris said.
‘We don’t understand the exact cause of death in each athlete, and some swim deaths may be related to drowning.’
Since its origin in the 1970s, the triathlon has become an increasingly popular endurance activity worldwide.
A standard Olympic triathlon involves a 1.5 kilometer (0.9 mile) swim, followed by a 40 kilometer (24.8 mile) bike ride and a 10 kilometer (6.2 mile) run.
For the study, researchers examined data on triathlon participants from 1985 to 2016.
During the study period, 135 people died suddenly or had a cardiac arrest.
This included 107 sudden deaths as well as 13 race-related cardiac arrests that people survived because of prompt emergency medical attention.
The victims were 47 years old on average, and 85 percent were male.
Overall, 90 deaths and cardiac arrests occurred during the swimming portion of races, while seven happened during cycling, 15 occurred while running and nine happened during the recovery period right after the race.
During the cycling segment, there were also 15 trauma-related deaths involving crashes or other accidents.
Autopsy data showed that clinically silent cardiovascular disease was present in an unexpected proportion of decedents, suggesting a need for participants to know their risk before racing.
The incidence of cardiovascular events was strikingly lower in female triathletes, 3.5-fold less than in men.
Death risks also increased with age. Among men 60 and older, 19 participants died or suffered cardiac arrest out of every 100,000 competitors.
One limitation of the study is that researchers used race finishers in their estimates, which might underestimate the risks associated with triathlons, the authors note.
Even so, the results should serve as a reminder to participants to make sure they are medically fit to compete in these endurance races, said Dr. Reginald Ho, author of an accompanying editorial and a professor of medicine at Sidney Kimmel Medical College of Thomas Jefferson University Hospital in Philadelphia.
‘They should see their physician regularly for health checks that include a complete history and physical examination,’ Ho said.
‘Any heart-related symptoms (chest tightness, heaviness or discomfort, shortness of breath, palpitations, lightheadedness, passing out episodes) should be reported to their doctor.’
The study results, however, shouldn’t overshadow the many health benefits of exercise or dissuade otherwise healthy people from considering endurance races, said Hannah Arem, a researcher at the George Washington Milken Institute School of Public Health in Washington, D.C., who wasn’t involved in the study.
‘For the majority of individuals, engaging in regular exercise will yield more benefit than harm,’ Arem said.