Lab Report: Health, Science and Medicine

EXERCISE

The Heart Hazards of Running a Marathon

Running for exercise is a great way to get the heart pumping and keep it healthy, but new research reveals that long-distance racing can take a toll, especially in those who aren't fit.

In a study of 20 runners with various levels of race experience, scientists found that immediately after completing a marathon, the runners' hearts were almost indistinguishable from ones that had been seized by a heart attack. The runners' hearts showed more inflammation, high levels of a stress enzyme that rises during a heart attack and increased amounts of dying heart muscle than they did before the race.

But there was an important difference: unlike with heart-attack patients, the damage in the runners' hearts was temporary and reversible. Three months after the marathons, images revealed hearts with normal function and no signs of having been under duress. The authors say their findings should not deter people from running a marathon, but they do highlight the importance of training properly. Runners who were more fit before their race experienced less short-term damage to their hearts than those who were less fit.

CANCER

Re-evaluating the Risks of Radiation

Radiation exposure is a potential cancer promoter since it can trigger mutation in healthy cells. But researchers had long thought that the risk of developing cancer this way was lower in adults than in young children, whose rapidly dividing cells make them more susceptible. Now scientists report that this assumption may have been wrong and that middle-aged adults may actually have twice the risk of radiation-induced cancers than previously thought.

In a new analysis of cancer rates among U.S. adults and Japanese atomic-bomb survivors, a team at Columbia University concluded that previous estimates of radiation risks may have underestimated one key factor: the accumulation of precancerous cells in adults. These cells, which increase in number with age, need only the slightest provocation--from, say, exposure to radioactive waves in cosmic energy or X-rays and other medical tests--to turn malignant. With increasing exposure, the cancer risk rises. The findings are particularly applicable to screening tests, like whole-body X-rays of healthy individuals, in which the potential benefit of finding an abnormality may not outweigh the risk of developing cancer from the radiation, say the authors.

FROM THE LABS

No Love Life? Blame Sisters

Your siblings may have a lot to do with how attractive you are to future mates, at least if you're a rat. In a study, male rats who were raised with more sisters than brothers were less sexually appealing to females than males raised with more brothers or an even split. But men with sisters need not fear: those male animals were just as efficient at mating as other males.

Of Bacteria and Broccoli