MEDICUS MARCH 2016

Q & A

Exercise-associated hyponatremia can kill Doctors are pouring cold water on the habit of drinking excessive amounts of fluid during exercise

T he nutritive and beneficial qualities of water have been known since the very beginning of time. In fact, keeping hydrated is considered a critical component of any exercise regime. Yet recent research has created some ripples in the pond by suggesting that drinking excessive amounts of fluid when exercising might not be so beneficial for our health after all. Prof of Emergency Medicine, Ian Rogers,

altered mental status such as confusion. In extreme cases, it can lead to seizures and even death. Although globally rates of EAH are low, it has been reported across a large cross- section of sports and activities. Athletes who have suffered with varying degrees of EAH include triathletes, soldiers, marathon runners, footballers, hikers, rowers, kayakers and Bikram (hot) yoga participants. In 2013, a participant in the Rottnest Channel

Professor Ian Rogers.

from St John of God Murdoch Hospital says the message to “drink, drink, drink” is a relatively new one and just a generation ago, people only drank when they were thirsty. “We now see everyone carrying water bottles and sports drinks to meet their assumed fluid quota for the day,” Professor Rogers says. “Not that long ago, people drank when they felt thirsty, which was just fine.” For athletes, keeping hydrated is seen as a critical component of performance ability, but when water, sports drinks and other hypotonic fluids are consumed excessively, the concentration of sodium can drop precipitously, with the kidneys unable to excrete the excess fluid. Cells then begin to absorb the water, which can lead to swelling all over the body – most seriously in the brain. This condition is known as exercise-associated hyponatremia (EAH) and its symptoms include headaches, vomiting and

Swim was treated for EAH after drinking excessive fluids. She ultimately recovered well, but only after specialist critical care treatment. Prof Rogers is one of an international panel of experts whose aim is to eliminate deaths associated with EAH. “These deaths, although rare, can be avoided with education about the dangers of drinking excessively,” Prof Rogers says. Prof Rogers was one of 17 international experts who convened in the US last year to review the current data and update previous guidelines on EAH. The delegates represented four countries and nine medical and scientific sub-specialties pertaining to athletic training, exercise physiology, sports medicine, water/sodium metabolism and body fluid homeostasis. Medicus asked PROFESSOR IAN ROGERS about EAH, its medical implications and the universal guidelines for its prevention.

later with groups in North America studying ultra-runners.

Q. What stimulated your interest in exercise-associated hyponatremia (EAH)? IR: Initially I started studying in the early 1990s what was then the new sport of multi-sporting – now known as adventure racing. As endurance sport participation became more common, it emerged that the most important medical problem in such events was exercise-associated hyponatraemia. I linked up with some researchers in New Zealand and South Africa studying Ironman triathlons, and

Q. How common/rare is EAH and who is most at risk? IR: Reported incidences vary from as high as 50 per cent in some ultra-marathon runners and 15 per cent in Ironman triathletes to less than 1 per cent in conventional 42km marathons. However, the races with really large numbers of participants are perhaps the most important, even though severe EAH is uncommon. There have been a number of deaths, and many near-misses from EAH in mass

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