marathon

Have you wondered about the “medical toll” at endurance sports events? By that, I mean the sum of all the medical problems that occur to atletes during their participation (and perhaps shortly afterwards as well).

It’s an interesting issue, with many practical implications. If you’re organizing a swim meet, you’d be interested in the likelihood of drowning. If you’re participating in a bicycle race, you’d be interested in the frequency of crash-related traumatic injuries. If you’re the spouse of a long-distance runner, you’d be interested in the likelihood of heart-problems for the participants of a marathon. Should your event have a “medical tent” to handle anticipated injuries or medical problems? Where should the medical tent be located and how should it be staffed? How should your local EMS system or hospital prepare to handle athlete-patients? You get the idea.

Yet surprisingly little has been written in the medical and scientific literature about the medical toll of endurance events. There’s probably a bunch of reasons, including the fact that nobody in particular’s keeping track.

This past week there was an interesting report in the British Medical Journal from a group of investigators in Cape Town, South Africa, and headed by Martin Schwellnus. The report, “Medical complications and deaths in 21 and 56 km road race runners: a 4-year prospective study in 65,865 runners–SAFER study I,” describes the “medical toll” at recent editions of the Two Oceans Marathon races. The report and the findings caught my eye.

The Study

The participants in the study were the 65,865 runners who took part in either the 21 km half marathon or 56 km ultra marathon, the premier events at the Two Oceans Marathon races that are held each year in Cape Town, South Africa. They focused on the 2008 through 2011 editions. The weather conditions for these races was generally favorable, with temperatures ranging from 11.5 to 18.2 degress C and relative humidity ranging from 77% to 93%.

Like many long distance running events, these races had an elaborate set-up for provision of medical care on race day, including on-route medical stations, a dedicated medical facility at the finish, and designated hospitals where athlete-patients would be transferred should they need emergency care. Because the system for medical care was so well proscribed, the investigators were able to compile a list of all “medical complications” that occured in the race participants.

The investigators did not consider the most minor of medical complications, such as seeking medical attention at various first-aid stations for minor injuries or requiring physical therapy attention at the finish line. For simplicity, “medical complication” was defined as an episode that required the attention of a doctor. Exercise-associated muscle cramps alone were not considered a “medical complication” unless there were additional symptoms such as confusion, dizziness, nausea, or vomiting. A serious medical complication was defined as a “medical complication that could result in death unless urgently diagnoses and treated.” And finally, deaths were recorded as well.

The Results

Of the 65,865 participants, 64,420 (97.8%) finished their race(s). The finishing rate was 99% for the 21 km races and 97% for the 56 km races.

Two deaths were documented, each in a 21 km race. The fatality rate, then, was approximately 1 per 20,000 participants in the 21 km races. There were no deaths in the 56 km races.

Overall, there were 545 medical complications among the 65,865 participants, a rate of approximately 0.8% (8.27 per 1000 participants). The rate was approximately 0.5% for participants in the 21 km races and 1.3% for participants in the 56 km races.

Included in the 545 total medical complications were 37 that were designated as serious medical complications. This is a rate of approximately 0.06% (0.56 per 1000 participants). There was no significant difference in the overall rate of serious medical complications based on the distance of the race. The serious life-threatening medical complications included:

Ischemic heart disease (including successful resuscitation from cardiac arrest), in 3 runners
Myocarditis, in 2 runners
Serious cardiac arrhythmias, in 2 runners
Symptomatic hyponatremia (low sodium), in 9 runners
Serious metabolic complications, in 5 runners
Serious heat-related disorders in 7 runners (1 with hypothermia, 6 with hyperthermia)
Pulmonary edema, in 2 runners
Serious fluid, electrolyte, or acid-base abnormalities, in 4 runners
Bronchospasm, in 2 runners
Convulsions, in 1 runner

Further statistical analysis was used to evaluate groups of medical complications, depending upon the body’s organ system that was involved. In this analysis, the frequency of complications involving the cardiovascular, musculoskeletal, metabolic, gastrointestinal, and respiratory systems was greater among the 56 km runners than for the 21 km runners.

The Takehome Messages

The chances of a medical complication or serious medical complication were small, for both of the race distances. Athletes should know, then, that these risks are small as they consider participation in an event.

Information like this should inform safety planning on the part of event directors, event medical directors, and events’ local medical communities.

I suspect that the results are generalizable to races outside of South Africa and also to the real-world question of half marathon vs. marathon races which would be typical distances in the United States.

It is a somewhat surprising finding that the only 2 deaths occurred in the shorter, 21 km races. We know from recent detailed studies involving millions of runners that the risk of sudden cardiac arrest at long-distance running events is almost 3 times higher for marathon runners than for half marathon runners. In this study, it’s a statistical oddity–that not enough years were considered to evaluate such a rare end point.

Intuitively, it is not surprising that there would be more medical complications in the longer events. If nothing else, there is more “time exposure”–more athlete-hours spent in strenuous exercise.

I am surprised, though, that the frequency of serious, life-threatening, medical complications was similar for the 2 race distances, I would have guessed that these, too, would be more common in the longer distance races. Perhaps the take home message is the converse–that a shorter race is not necessarily safer when it comes to life-threatening medical complications. And the real world consequence would be that half marathoners not give short shrift to their health before participating.

Lastly, I’ll continue to hope that national governing bodies and large event organizers (eg, World Triathlon Corporation [WTC[) might collect and disseminate information about the “medical toll” at their races. As a sporting community, we would all benefit.

Jackson, Mississippi hosted the 3rd annual Mississippi Blues Marathon this past weekend. The temperatures were bitter cold (17 degrees at the start), but 1,400 or so folks braved the cold to finish the marathon or half marathon events. I twisted my ankle about 10 days ago, or I might have joined my many running friends for the event.

The day was marred by the tragic death of a 40-year-old local man who died in the final mile while he was running the anchor leg for a 5-man relay team. He collapsed suddenly within sight of one of Jackson’s major hospitals. He received immediate medical attention, was taken to the hospital, and was pronounced dead. The events are described in this article from the local Clarion-Ledger newspaper. The coroner did not immediately release a statement about the cause of death.

I’ve received many questions since Saturday about this tragedy and I thought I’d share some of my thoughts here at the blog.

I’ve talked previously here at the blog about causes of death in middle-aged athletes. Here again, the most likely cause of death is cardiac, and specifically a fatal arrhythmia in the setting of coronary artery disease (CAD). A variety of other causes is possible, though, and we will only learn the true cause when an autopsy is completed. Other possibilities would include undetected hypertrophic cardiomyopathy (HCM), some sort of congenital heart disease, or even catastrophic neurologic event such as a stroke.

I’ve been asked about the role that the cold temperature on race day might have played in this runner’s death. It’s an interesting question. Since there are only a handful of deaths annually in the U.S. at marathons, the issue of race-day temperature on the risk of sudden death hasn’t really been studied….and probably can’t be studied. I recall that it was also a cold day in Detroit this fall when 3 runners died of cardiac causes at the Detroit Marathon. Thankfully, deaths at marathons are rare, at only 1 per ~100,000 runners.

If we think about this problem OUTSIDE the setting of athletic pursuits, it turns out that cold temperatures actually ARE associated with an increased frequency of heart attack. We know this from studies that show that heart attacks occur more often in the winter. And it’s generally thought that the cold temperature itself produces some sort of extra stress that might trigger the heart attack. That said, the effect of temperature is relatively small….and heart attacks occur in all temperatures.

We often think about the added stress that HOT or HUMID weather places on athletes in endurance events. But the cold can also add stress. The issues related to cold-weather running are summarized very nicely by Tim Noakes, MD, in his book, Lore of Running, in a section called Cold Hazards. The most important medical concern during cold weather running is hypothermia. And, interestingly, the slower you run (or walk), the more important it becomes to dress warmly.

And lastly, what could have been done to prevent this death? Without more information about his cause of death, I can’t be sure. And I don’t know anything about this runner’s medical history or preparation for the event. Perhaps nothing could have been done. But I’ve said it here at the blog before….if you’re a 40-year-old endurance athlete, it is wise to have a physician, get screened for possible unrecognized heart disease, and treat all warning signs such as chest pain or unusual shortness of breath seriously. Get checked out. And make certain that your goal event makes sense in the context of your medical condition and your athletic preparation for the event.

Writing on…

The Medical Toll at Endurance Events