BOSTON (Boston Globe) - Running a marathon may increase the risk of heart attack even for healthy and fit people by thickening their blood in the 24 hours after the race, according to a study by researchers at McLean Hospital and other area medical centers.
With more Americans taking up marathoning every year - 451,000 finished at least one of the 26-mile races in 2000 - the researchers suggest that doctors need to explore how to make the sport safe, especially for runners over age 30.
"Runners need to understand not only the benefits of regular exercise, but the risks of extreme exercise," said Dr. Arthur Siegel, a former marathoner lead author of the study published Wednesday in the American Journal of Cardiology.
"The marathon is not the holy grail of cardiovascular benefit," said Siegel, director of internal medicine at Mclean. The increase in blood clotting and inflammation he found in marathoners 24 hours after a race "loads and cocks the gun" for a heart attack, Siegel said, although a complication such as cardiac arrhythmia or dislodging of a blood clot is typically needed to trigger an attack. An earlier study by Dr. Barry Maron of the Minnesota Heart Institute Foundation found about one sudden death from heart-related problems for every 50,000 marathoners.
About 15,000 people ran the Boston Marathon this year. In the last five years, there has been one reported death from heart attack at the race. Siegel's study analyzed the blood of about 80 healthy doctors who have repeatedly run the Boston Marathon. A day after the race, he found an imbalance in clotting and inflammatory factors known to set the stage for a heart attack. Those factors - including white blood cell counts, von Willebrand factor, and D-dimer - remained high, while blood thinners, which had also risen immediately after the race, dropped back to normal levels. None of the doctors studied suffered any heart trouble.
"There is apparently a transient risk, and there could be some subtle injury happening," said Siegel, 61. He said he quit marathoning in the late 1980s when he couldn't keep up the training regime. "It's difficult to give a true balance sheet on marathon running, because most of the people who do it would do it despite the risk," said Dr. Gene Lindsey, a cardiologist at Harvard Vanguard Medical Associates and a marathoner who participated in earlier studies by Siegel.
"But this study suggests that perhaps we ought to be a little more careful in how we screen them and monitor them," Lindsey said. Both Lindsey and Siegel said marathoners should take low doses of aspirin to help ward off any heart trouble and consult their doctors about whether to take statins, a class of prescription drug that also reduces the risk of heart disease.
"To young people, I say, go out and enjoy the training and the sport," said Siegel. "But I have reservations about people in their 30s and 40s doing this to promote their cardiovascular health." To doctors, Siegel issued a separate warning: Be careful when using tests to determine whether runners are suffering heart attacks. In a separate study on the same group of doctor-marathoners, Siegel found that they tested positive for a marker commonly used in emergency rooms for early detection of a heart attack. The high reading of creatine kinase-MB, he said, might be the result of injured skeletal muscle in runners, instead of injured heart muscle, because none of the marathoners had other symptoms of heart trouble and none showed abnormal levels of cardiac troponins, a late-stage marker for heart attack.

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