ORLANDO — The risk of sudden death during a triathlon is two- to three fold greater than in running a marathon, according to the first large-scale mortality study of participants in the popular swim-bike-run events.
The risk appears to be essentially confined to the swim portion—traditionally the first stage—and it is twice as great in men than in women, Dr. Kevin M. Harris reported at the annual meeting of the American College of Cardiology.
He studied 2,846 triathlons sanctioned by USA Triathlon, the sport's governing body, during 2006–2008. Of the 922,810 participants, 80% were male. Of 14 deaths, 13 occurred during the swim portion and 1 involved a fatal bike accident. The mean age of participants who died was 43 years (range, 28–55 years). Eleven men and three women died, for mortality rates of 2.0 and 0.8 per 100,000 male and female participants, respectively.
Sudden deaths were roughly equally distributed among triathletes in sprint or short-distance triathlons, intermediate Olympic-distance courses, and very long Ironman-type events, said Dr. Harris, director of echocardiography at the Minneapolis Heart Institute.
Autopsy reports were available for six water deaths. Three found evidence of hypertrophic cardiomyopathy and one showed the presence of dilated cardiomyopathy. A plausible scenario is that the athletes with underlying cardiomyopathy died of arrhythmias induced by the cold water or intense competitive exertion, while the others may have simply drowned. Most athletes train in a lap pool under far tamer conditions than those encountered in an open-water swim, the cardiologist noted.
The overall sudden death rate among triathletes was 1.5 per 100,000 participants. In contrast, the sudden death risk in marathon runners was 0.8 per 100,000 in the largest-ever study (BMJ 2007;335:1275–7), and 0.45/100,000 runners in another contemporary series (J. Am. Coll. Cardiol. 2005;46:1373–4).
In the biggest marathon study, with more than 3.2 million runners, University of Toronto researchers estimated that because of road closures during the races, roughly 1.8 motor vehicle crash deaths were averted for each case of sudden death in a runner, resulting in a net societal benefit.
The sport of triathlon is booming in popularity. Membership in USA Triathlon climbed from 15,000 in 1993 to more than 100,000 in 2007.
Dr. Harris' study was supported by the Minneapolis Heart Institute Foundation.
Most athletes train in a pool, in tamer conditions than an open-water swim. ©