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DISCOVERIES

Researchers solve mystery of 2002 Marathoner's death

When Cynthia Lucero died while running the 2002 Boston Marathon, apparently from drinking too much water, doctors didn't really understand the disorder they called exercise-associated hyponatremia, or EAH . Now, a new study, helped by research from more recent Boston Marathons, suggests that the problem was hormonal. The stress of running the marathon apparently can disrupt the hormone that governs water balance, basically causing cells, including brain cells, to swell with water. "This is a major paradigm shift for those who think that EAH is due primarily to salt loss or over consumption of fluids," said Arthur J. Siegel, the lead researcher and chief of the department of Internal Medicine at McLean Hospital. Although anyone can experience hyponatremia, slower, inexperienced runners appear to be at greater risk, since they lose less water through perspiration than those in better shape, he said. Knowing the cause has important implications for treatment of hyponatremia. At this year's Boston and Marine Corps marathons, the research team found that giving runners concentrated bouillon or delivering a 3-percent intravenous saline solution can help reverse symptoms of hyponatremia by pulling fluid out of cells, Siegel said.

BOTTOM LINE: Researchers now have a deeper understanding of and an effective treatment for hyponatremia, a potentially fatal form of water intoxication that can affect marathoners and other extreme athletes.

CAUTIONS: The study was small and largely observational.

WHAT'S NEXT: Siegel is trying to raise awareness of the team's findings and encourage marathon organizers to have proper treatments readily available along the race route.

WHERE TO FIND IT: The American Journal of Medicine, May

AMI ALBERNAZ

ENVIRONMENT Cutting traffic for a few days reduces pollution in China

Hoping to avoid embarrassing the country during the 2008 Olympics, the Chinese government has taken a number of actions to reduce the smog that regularly hangs over Beijing. Now, a Harvard study suggests that one effort, at least, will make a major difference. Researchers reported a 40 percent decline in nitrous oxide emissions -- the pollution commonly associated with cars -- during a three-day period in 2006 when the government severely restricted car traffic in the capital city. Post-doctoral fellow Yuxuan Wang, the study's lead author, noted that the drop in emissions was much larger than expected for the 30 percent reduction in traffic, raising the possibility that the government could have underestimated the actual traffic reduction achieved by the restrictions. More periods of traffic restrictions are planned in Beijing this summer in preparation for the 2008 Olympic Games, as well as during the Games themselves. "We can take advantage of those natural experiments," she said.

BOTTOM LINE: Three days of traffic restrictions in Beijing had a significant impact on pollution, suggesting both a short-term fix and a long-term way to limit China's contribution to global warming.

CAUTIONS: The results are estimates, not actual measurements of the nitrous oxide levels .

WHAT'S NEXT: Wang and her colleagues plan to obtain more detailed data in future studies.

WHERE TO FIND IT: Geophysical Research Letters, April 28.

MICHELLE SIPICS

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