Is the triathlon swim fatal?

Swim-leg of a triathlon. Photo from “4 tips for a safe triathlon swim”:

Apparently, according to this report of a study, triathletes die during their races at two to three times the rate of runners during marathons. That’s 1.5 triathletes out of every 100,000. And of those triathletes who die during their races, most  (more than 72%) meet their end during the swim.

That may seem unsurprising, given the potential for drowning. But you might wonder why perfectly good swimmers end up drowning. It’s not that they get dragged under by others or caught in the weeds or tossed around by rough seas, though these things might happen.

No, researchers now speculate that it’s because of immersion pulmonary edema (IPE). According to this report:

IPE, also known as swimming-induced pulmonary edema, occurs when the lungs suddenly fill with body fluids during activities in cold water, such as swimming and diving. IPE can lead to difficulty breathing, wheezing and confusion, which can be serious and even fatal.

Does this mean that all triathletes are at risk (and what about divers?)? Not likely. Dr. Richard Moon, first author on the study, says that:

its onset is often seen in those with left ventricular hypertrophy (LVH), a condition where the heart muscle becomes thickened or heart mass increases. LVH typically occurs in people with high blood pressure and is a marker for susceptibility to IPE. A mildly enlarged heart — commonly referred to as athlete’s heart — can also develop among endurance athletes, although athlete’s heart is not believed to predispose to swimming-induced pulmonary edema.

Studying autopsy reports, Moon and his team discovered that the deceased triathletes had “a much higher prevalence of LVH than the healthy athletes” and a higher degree of heart enlargement.

The link isn’t a conclusive finding, but Moon sums the significance of the findings up like this:

“The message is that if people have untreated hypertension or they’re known to have ventricular hypertrophy, they need to get evaluated and treated before they embark on this sport,” Moon said.

I’m no doctor (or at least not that kind of doctor), but if cold water can bring this on, then it might be another good argument for wearing a wetsuit.

I would be interested to know a few things about this study and it’s always tough to know how reading about a study should alter our behaviour. These are the questions I would ask if I could have a sit-down with these researchers:

1. What do they mean by “cold” when they talk about “cold water”

2. Were the deceased athletes wearing wetsuits

3. Would wearing a wetsuit make a difference if you had this condition?

4. Are triathletes with this condition at risk at all race distances or just in the more taxing endurance distances?

What about you? Do reports of this kind figure on your radar much when you’re deciding about activities? 

If you do have untreated hypertension it’s probably worth taking Moon’s advice seriously.


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