Exercise-associated hyponatremia; drinking oneself to death….. Guest blog by Dr Jonathan Williams

A 22 year old male fitness instructor finished the 2007 London Marathon, collapsed, and despite immediate emergency medical care, died. His serum sodium was markedly low, and the cause of death was found to be hyponatremia. Subsequent investigations established that he had been concerned about becoming dehydrated, and had therefore drunk a large volume of fluid en route. Several other athletes have died from hyponatremia due to drinking excessively, and many others have required hospital care. Studies from the 2002 Boston Marathon and 2006 London Marathon found that 13% and 12.5% of finishers, respectively, had asymptomatic hyponatremia. Our paper in this month’s CJSM explored the 2010 London Marathon runners’ knowledge about fluid intake, their drinking strategies and knowledge about exercise-associated hyponatremia (EAH).

City marathons were established around the world in the 1970s and 1980s. Elite marathon runners of the time rarely drank much during races; when Mike Gratton won London Marathon in 1983, he drank nothing. However, in 1975, the American College of Sports Medicine published a position statement advocating regular fluid intake during endurance events, suggesting this would reduce the risk of heat stroke. During the 1980s and 1990s, increasing numbers of endurance athletes experienced EAH.  International EAH Consensus Development Conferences of 2005 and 2007 reviewed the available evidence about EAH, and advocated drinking “to thirst” rather than the higher volumes recommended by ACSM. In 2007, ACSM revised its position statement advising that fluid intake during exercise should not exceed sweat loss.

In our study, a representative sample of 217 runners was questioned. More than 93% of the runners had read or been told about drinking fluid on marathon day. However, 12% planned to drink a volume large enough to put them at higher risk of EAH, and only 25.3% planned to drink according to their thirst. Although 68% had heard of hyponatremia or low sodium, only 35.5% had a basic understanding of its cause and effects. These findings suggest that runners lack knowledge about appropriate fluid intake on race day. Effective education is needed to prevent overdrinking during marathons.

Professor Tim Noakes has researched EAH for almost thirty years. He is due to publish a book in May 2012 called ‘Waterlogged’ in which he explores the influence sports drink manufacturers have on the science of hydration, and on runners’ drinking habits. ‘Waterlogged’ is likely to be thought-provoking, controversial and fascinating.

The cause of EAH is firmly established and it is entirely preventable. It is now the responsibility of race organizers, drinks manufacturers, running publications and us as sports physicians to educate runners effectively about safe drinking strategies.

Dr Jonathan Williams is a Sports Medicine Doctor and General Practitioner, as well as an avid runner.

The photograph is of the author having just completed a London Marathon

References :

1) Williams J et al. 2012. Hydration Strategies of Runners in the London Marathon. Clin J Sport Med 22 (2): 152-156

2) Hew-Butler et al. 2008. Statement of the Second International Exercise-Associated Hyponatremia Consensus Development Conference, New Zealand, 2007. Clin J Sport Med 18(2): 111-121

3) Hew-Butler et al. 2005. Consensus Statement of the First International Exercise-Associated Hyponatremia Consensus Development Conference, Cape Town, South Africa 2005. Clin J Sport Med 15(4): 208-213

4) Sawka MN et al. 2007. ACSM Position stand – Exercise and Fluid Replacement. Med Sci Sports Ex 39 (2): 377-390

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About Chris Hughes
Associate Editor, Clinical Journal of Sport Medicine

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