Running: why do runners die during marathons?

Joe English – 12:29 pmCoach Joe English
Coach Joe English

With the death of a runner in the Little Rock Marathon two weeks ago, as well as deaths in the 2007 Chicago Marathon and the 2007 US Men’s Olympic Trials, a number of people have recently asked the question, “why do runners die during marathons?”
After doing some research and drawing on my own anecdotal experience, I can offer some general conclusions about what causes marathon runners to die during races – and hopefully we can use this information to help avoid any of the situations that might be highlighted here.

Keep in mind that we’re speaking in generalities about a sport in which hundreds of thousands on unique individuals participate each year. We all need to be mindful that marathon running is a difficult physical endeavor, but it is not necessarily an inherently dangerous activity. A study on London Marathon runners over a 20 year period, in fact, found that with a rate of death of 1 in 67,414 (representing 1 in 2,000,000 miles run) marathon running was no more dangerous than many other daily activities.

See also our Episode 26 of our video series as we discuss this issue by clicking the play button in the window below.

The four major circumstances that lead to marathon runner deaths appear to be: heart disease in runners over 35 years; genetic heart defects in runners under 35; hyponatremia or low blood sodium levels; and heat related illnesses, such as heat stroke.

Heart Disease or Coronary Artery Death
One of the most common causes of death in runners during marathons is heart attack caused by underlying coronary artery diseases. These heart attacks are brought on by the combination of the intense physical stress of running for an extended duration and the pre-existing disease in the runner’s heart or a lack of cardiac fitness to handle the race.

This type of death typically occurs in runners that are over the age of 35 and can occur even in races as short as half-marathons. Coronary Artery Deaths are most common if the race is conducted under hot and humid conditions, which places additional stress on the heart as it struggles cool the body.

During a long running event, the heart comes under more and more stress as the body begins to fall into exhaustion. If dehydration starts to set in, the heart will work even harder to push a diminishing volume of blood through the body. This combination is extraordinarily hard on the heart and if the heart already suffers from heart disease, the combination can be fatal. The US Registry of Sudden Death in Athletes found that about 14% of all sudden athlete deaths could be attributed to coronary artery deaths.

Medical experts, such as Dr. Lewis Maraham, point out that it is especially important for people that have been sedentary (out of shape) and decide to undertake a tough endurance event should “undergo a treadmill stress test with an echocardiogram to record the heart’s performance.”

Heart Defects or Sudden Cardiac Death
Another factor that can cause deaths in younger runners is the presence of a genetic defect in the heart itself that hasn’t previously been detected or treated. A number of heart conditions can lead to a sudden failure of the heart, including hypertrophic cardiomyopathy or HCM. According to an article in MedicExchange, this condition is characterized as:

“a relatively uncommon disorder in which the heart muscle becomes enlarged, interfering with normal cardiac function. Thickening in muscle fibers is usually greatest in the walls of the left ventricle, the heart’s main pumping chamber. This thickening reduces the size of the pumping chamber itself, which in turn hinders blood flow. HCM has been implicated in the sudden deaths of some young, fit individuals.”

A study detailed in the article notes that the condition is exceedingly rare in elite athletes, occurring at a rate of no more than 0.06%. The rate in the general population is about 0.2%. As a cause of sudden deaths in athletes, according to the US Registry again, the rate was about 26% of athlete deaths – but keep in mind that this includes deaths in all sports, not just running.

There has been speculation that elite marathon runner Ryan Shay may have died of an enlarged heart that caused a sudden heart attack in the US Olympic Trials last November. As of this writing, the autopsy report had not yet been released to give us the exact cause of death – a delay that has caused some frustration in the running community.

Hyponatremia and hyponatremic encephalopathy
Hydration issues have long been a concern for marathon runners. But in the last few years there has been an increase in the number of deaths from a condition called hyponatramia or “water intoxication” as it is more commonly known. The condition is a health-threatening sodium deficiency that can in a rare cases be fatal.

The body sweats to cool itself while running and sodium is lost in this fluid. Runners that have been trained to drink plenty on the race course at times drink large enough amounts of plain water, which contains no sodium., leading to a dilution of the sodium level in their blood. As blood sodium levels drop, this can lead to a condition called hyponatremic encephalopathy.

The process involved is actually quite complex. As explained in an article on the death of a runner at the Boston Marathon in 2003,

“[athletes] in extreme sporting competitions often deplete the fuel that powers the body’s cells. When this happens, a hormone called arginine vasopressin gets released. Part of its function is to tell the kidneys to hold on to fluids. That, in turn, precipitates an imbalance in sodium levels in the blood. But as salt drops in the blood, it does not do so in cells. The body, in its constant pursuit of equilibrium, attempts to force salt out of cells by flooding them. That causes swelling. Muscles can endure such swelling because they can bulge outward. The brain, though, cannot.”

The swelling in the brain is what is fatal in these cases.

Avoiding hyponatremia is a matter of replenishing both fluids and electrolytes, including sodium, while running. Runners need to ensure that they learn to drink the proper amount of fluid for their sweat level and then how to adjust this for extreme temperatures.

Heat related illnesses
Another group of potentially life-threatening conditions come in the form of heat related illnesses, mostly caused by extreme dehydration. As the body becomes dehydrated, it loses the ability to regulate its temperature and as its temperature rises, the result can be heat exhaustion, heat stroke, heat induced coma and then death. For an excellent discussion of the process through which the body goes through in a marathon in heat, see this 2005 article written after four runners died in the Great North Run in England.

All runners should learn how to keep themselves cool when running in hot weather. Running in extreme heat is essentially always life-threatening, but so long as you hydrate, slow your pace, and take actions to keep yourself cool, it can be managed. You can read additional articles on this site about racing and training in hot weather and hydration basics to learn more about this important subject.

While there are dangers in marathon running, as I said at the outset, marathon running itself is not inherently more dangerous than other activities. Before undertaking a marathon training program, get a thorough physical exam from your doctor. From there, make sure that once race day comes that you are fit enough for the challenge and always remember to take actions to avoid dehydration, sodium loss and the impact of heat on your body.

Coach Joe English
Running Advice and News

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Filed under: Marathon Running Tags: causes of deaths in marathons, Marathon Runner Deaths, Marathon Running, Marathon Running Fatalities, Running, running deaths
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13 responses so far, want to say something?
1. Tracy HelmuthMarch 13th, 2008 at 2:09 pm

Great information, Coach! So hard to hear stories of losing runners.:(
2. Why do runners die during marathons? | trailrunningSoul.comMarch 14th, 2008 at 1:03 pm

[…] but usually not in-depth medical explanations. Joe English, coach and blogger, details some of the usual causes that may end up in a death in an endurance competition: heart disease, heart genetic defect or low blood sodium levels. His post is based on research and […]

3. Risk Management as a Biz Topic « MultisportBizMarch 16th, 2008 at 11:46 am

[…] but usually not in-depth medical explanations. Joe English, coach and blogger, details some of the usual causes that may end up in a death in an endurance competition: heart disease, heart genetic defect or low blood sodium levels. His post is based on research and […]

4. Follow-up: Cause found in death of Little Rock Marathon Runner « Running Advice and NewsApril 9th, 2008 at 11:23 am

[…] an article I posted at the time, I discussed the four most likely causes of death in marathon runners. The most common of these among younger men are undetected heart conditions, like the one that […]

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6. GeorgeOctober 14th, 2008 at 5:22 pm

This is an interesting article and should be expanded upon. I know this is of great concern and interest to many runners. In the 2006 LA Marathon, two retired law enforcement officers died after collapsing on the route. One runner age 53 suffered a heart attack at mile 24 near Olympic Boulevard and Westmoreland.
The other runner age 60, collapsed at mile 3, near Exposition Boulevard and Figueroa Street. My prayers go out to those runners.
Your article about water intoxication is interesting. No wonder they give out pretzels at the races. I am wondering if there is a problem with drinking too much gatorade.

7. Joe EnglishOctober 14th, 2008 at 9:15 pm

In answer to George’s question, there is generally not an issue in drinking too much of an electrolyte solution (such as Gatorade).

The worry is always with drinking too much plain water and thus dilluting the sodium level in your blood. When sodium levels fall too low, the mechanism that allows chemicals to move in and out of cells (osmosis) fails and then the cells are not able to get the chemicals they need to function properly.

Coach Joe

8. Races: Two runners die after 2008 ING New York City Marathon « Running Advice and NewsNovember 5th, 2008 at 1:59 pm

[…] Typically, marathon deaths are caused by one of four factors: 1) previously undiagnosed heart conditions, 2) heart attacks related to heart disease, 3) heat related illness and 4) hyponatremia or a low level of blood sodium that is typically caused by over-drinking of plain water. You can read an in-depth article on these causes in an article I wrote last year, by clicking here. […]

9. PatrickDecember 15th, 2008 at 2:10 pm

Another fatality this weekend at Dallas White Rock Marathon, a 29 year old female experienced distance runner collapsed at mile 21, responded to commands for a few minutes then died instantly. I was running as well although a few miles behind her, I heard the emergency vehicles trying to get to her.

10. Joe EnglishDecember 15th, 2008 at 3:40 pm

Thank you Patrick for the note. I was just writing and article about this story.

Look for more details soon.


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[…] The heat lead to unusually high numbers of runners being transported to local hospitals for treatment. One runner, a man in his mid-20s, is reported to have died of a cardiac event immediately after finishing the race. To read more about the causes of marathon runner deaths, click here. […]

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[…] There are a number of common reasons for runner deaths in marathons. In races run in cool weather, the most common causes are undiagnosed heart conditions or previously undetected heart disease. You can read more about the causes of marathon deaths in our article “Why do marathon runners die during marathons?” […]