Marathon running: small or increased risk for cardiac arrest?

Abstract

On Thursday 12 January 2012, the headline of ACC News Digest reports that the Risk of cardiac arrest for marathon participants may be very small. This news sounds very reassuring and stimulating for participants in marathons. However, one day later, Friday 13 January, the Dutch Newspaper NRC Handelsblad publishes the following scoop: An increasing number of individuals die during marathon running. By contrast, this news sounds alarming and discouraging rather than stimulating for marathon runners. Initially, my perception was that both news facts were based on different studies. However, the data proved to be based on the same study, published 12 January in the New England Journal of Medicine (NEJM 2012;366:130–140) by the Race Associated Cardiac Arrest Event Registry (RACER) Study Group, chaired by Kim et al. from Harvard Medical School, Boston, USA [1]. So what is the true news here. Let us therefore a take a deeper look into the study itself. The authors evaluated the occurrence of cardiac arrest during long-distance running in the USA during a 10-year period from 1 January 2000 to 31 May 2010. The investigators found that out of almost 11 million runners, there were 59 instances of cardiac arrest, of which 42 were fatal cardiac arrest (incidence rate 0.39 per 100,000 participants). The rate of cardiac arrests was higher among men than women (0.90 per 100,000 versus 0.16 per 100,000), and also higher among marathon participants than those running in half-marathon events (1.01 per 100,000 versus 0.27 per 100,000). These overall figures translate into 1 cardiac arrest per 184,000 participants and 1 death per 259,000 participants. According to the researchers, these numbers are low compared with other athletic activities, as shown by previous studies of deaths in college athletes, triathlon participants and previously healthy middle-aged joggers. Marathon running may even be safer than every-day running as the rate of sudden death among regular joggers has been estimated at 1 in 7620 per year. Cardiovascular disease accounted for the majority of cardiac arrests. Particularly in male runners, cardiac arrest may be due to early onset of atherosclerotic disease, but also occult hypertrophic cardiomyopathy should be considered as a major cause of sudden cardiac arrest. Male marathon runners showed an increased incidence of cardiac arrest during the latter half of the study decade. When comparing the study period 2000–2004 with 2005–2010, the incidence increased significantly from 0.71 per 100,000 to 2.03 per 100,000. According to the authors, this finding may indicate that long-distance racing has recently been attracting more high-risk men with occult cardiac disease who seek the health benefits of routine physical exercise. Future work is needed to further characterise this group and to determine useful prevention strategies. The RACER study group therefore provides a number of new insights into marathon-related cardiac arrests. First, the absolute number of race-related cardiac arrests each year increased over the past decade, which may be due to an absolute increased number of (particularly male) participants (2000–2004, 4,523,000 participants; 2005–2010, 6,348,000 participants). Second, men were more likely than women to have cardiac arrest and sudden death. Third, race distance was a determinant of the incidence of cardiac arrest and death, with rates for marathons that were 3–5 times higher than the rates for half-marathons. Finally, cardiovascular disease accounted for the majority of cardiac arrests. Hypertrophic cardiomyopathy, the primary cause of death in young competitive athletes, was also a leading cause of death in this population. To conclude, marathons and half-marathons are associated with a low overall risk of cardiac arrest and sudden death. Although event rates have risen over the past decade among male marathon runners, this increase mainly stems from a greater number of participants. The Boston researchers therefore advise that clinicians, evaluating potential race participants, should be aware of the risks of atherosclerotic disease and hypertrophic cardiomyopathy in marathon runners. Finally, to answer the question which of news media (ACC News Digest versus NRC Handelsblad) brought the true news. In fact, both did. In my opinion, however, the optimistic view should prevail as the overall risk of a cardiac arrest during marathon running remains very small despite an increase in male runners over the past 5 years. Why discourage long distance running as this activity promotes physical health and mental well-being in the overwhelming majority of sportive individuals.