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Triathlons - what do participants die of?

Dr Chee L Khoo

Triathlons are a very gruesome competitive sport consisting of swimming, cycling and running. Common race lengths are Sprint (750m swim, 20km ride, 5km run), Olympic (1.5km swim, 40km ride, 10km run) and Ironman (3.9km swim, 90km ride, 42.2km run) but there are a variety of race length available. It’s an increasingly popular endurance activity worldwide.

According to data from USA Triathlon (USAT), the U.S. governing body for the sport, more than 3200 sanctioned adult events involving more than 460 000 participants took place in 2015 alone! Not unexpectedly, race related fatalities have also increased and now is growing concern amongst participants who is generally thought to be cardiovascularly “fit”. Most of us have a handful of patients who are triathletes and a recent study is both insightful and have implications of our treatment of these “healthy” individuals.

Kevin Harris et al prospectively and retrospectively identified race-related deaths and cardiac arrests occurring during triathlons in the United States between 1985 and 2016. Data came from from USAT record and the U.S. National Registry of Sudden Death in Athletes (4, 5), which uses news media reports, Internet searches, LexisNexis archival databases, and news clipping services and personal reports from interested parties. Additional information regarding the medical background of victims and race conditions was obtained through contact with next of kin or race directors. Deaths occurring during triathlon training, USAT training camps, events other than traditional swim–bike–run triathlons, and races occurring outside the United States were excluded.

Between 1985 and 2016, they uncovered amongst 9 million participants:stick_figure_buoy_exhausted_400_clr_6690


Total 135 deaths or cardiac arrests - 122 sudden deaths & 13 cardiac arrests

  • Average age 46.7 yo +/- 12.4 years; 85% male
  • 67% occurred during swim segment, 16% during bike, 11% during run and 8% during recovery
  • 38% competing in their first triathlon – mostly (69%) in the sprint event rather than the longer ones
  • Average air temperature 21.9 ⁰C (range 6.7 ⁰C - 28.9 ⁰C)
  • Average water temperature 22.1 ⁰C (range 10.6 ⁰C -31.7⁰C)
  • The rate of deaths and cardiac arrests per 100 000 participants was 3.3-fold higher for men aged 40 years and older than for those younger than 40 years

Causes of death

Autopsy reports were available only in 61 cases. Of the 61 cases, 27 (44%) had cardiac abnormalities:

  • 18 Coronary artery disease
  • 3 Hypertrophic obstructive cardiac myopathy
  • 2 Mitral valve prolapse
  • 1 Wolf-Parkinson-White
  • 1 Ascending aortic dissection
  • 1 spontaneous renal artery rupture
  • 1 right ventricular cardiomyopathy

Sudden death and cardiac arrests during triathlons are not rare events. The incidence of 1.74 per 100 000 participants are higher than marathons (1 per 100 000) and higher than sudden deaths in middle aged person in the general population.

Theories suggested to explain why swimming segment is more dangerous

  • Catecholamines surge early in the race (first leg being swim) may play a role in triggering arrhythmias  particularly in athletes with undiagnosed cardiovascular disease
  • Participants may not be adequately trained for open-water swimming with adverse environmental conditions including large waves and cold temperature
  • Water rescue may be logistically complex – crowding, difficult to spot and difficult to reach for resuscitation. 5 participants who had cardiac arrest during swimming but survived  thanks to proximity to rescuers as they occurred in the pool rather than open seas. The ratio of cardiac arrest survival to sudden death (11%) is much less favourable than that reported for the marathon (29%) and likely relates to the proximity of rescuers during the marathon (9) as well as the greater difficulties inherent in water rescue.

There is no doubt that triathlons are physically gruesome and not for the faint hearted. Mortality is higher than other endurance events and higher than the general population. A significant number of participants have underlying cardiac abnormalities previous undiagnosed. Men older than 40 years should consider the potential risks of triathlon competition and the value of screening for cardiovascular disease by their physicians.

The USAT has prepared a series of recommendations to improve race safety including a framework includes minimum standards for medical presence at races, water quality, on-water rescuers, and prospective notification of local emergency medical services and hospitals. They also suggested the elimination of mass starts (>2000 participants) to allow for easier recognition of participants in distress.

Luckily I only run marathons!


Harris K. et al. Death and Cardiac Arrest in U.S. Triathlon Participants, 1985 to 2016 - A Case Series. Ann Intern Med. 2017; Annals of Internal Medicine , Vol. 167 No. 8, 17 October 2017 167:529-535. doi:10.7326/M17-0847

Kim JH, Malhotra R, Chiampas G, d’Hemecourt P, Troyanos C, Cianca J, et al; Race Associated Cardiac Arrest Event Registry (RACER) Study Group. Cardiac arrest during long-distance running races. N Engl J Med. 2012;366:130-40. [PMID: 22236223] doi:10.1056/NEJMoa1106468

The views expressed are views of the authors and do not necessarily represent the views of the board of SSW GP Link

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