Tuesday, March 30, 2004

Exercise and Cancer in Women

You must have heard by now that abortion does not cause breast cancer. The debates surrounding this topic have taught me how political the field of women's health research can be. This makes it extra important to scan all new studies carefully for political motives. Sad but true: there are people in this world who are more interested in making political points than in improving the health of the general population or of any of its subgroups such as women. Also, researchers and media pundits are only human, and quite likely to have the same biases as the rest of the population.

So what does this have to do with exercise and its potential effects on cancer? A study has recently shown that women who exercise regularly after the diagnosis of breast cancer have a better survival record than those who don't exercise. The effect is larger the more the woman exercises, but even a leisurely half an hour spent walking each day appears to help the odds of survival.

Another study, which was carried out in China, looked at the relationship between lifelong exercise and the risk of endometrial cancer, the fourth most common cancer in U.S. women. The researchers found that:

...those who stayed active through exercise, housework and walking and cycling for errands had about a one-third lower risk of this form of cancer.

Here's where the politics comes in. Washington Times, the very conservative newspaper owned by the Reverend Moon, reported these findings in an article entitled "Housework Cuts Cancer Risk". It begins as follows:

U.S. and Chinese researchers said Tuesday that doing housework can reduce a woman's chance of getting cancer.

Only later does the reader find that the research findings apply to all ways of staying active. Someone just skimming the headlines and first paragraphs of stories might have gotten a very different idea of the message of the story, one perhaps more suited to Reverend Moon's political values.

Just to make my point very clear: you don't have to do housework to get any possible benign effects of exercise on cancer prevention; water-skiing, figure-skating or boxing will work just as well if not better. And it's a lot more fun. On the other hand, if you feel that you have to do housework, at least now you can feel happy that you are also working out at the same time. To strengthen the positive effects throw plates at the lazier family members.

But does exercise actually prevent cancer or its reoccurrence? The evidence looks pretty good. The only general reservation I have concerns the possibility that we might be measuring a reverse causality here: Breast cancer patients who feel poorly are less likely to exercise, and the reason that they feel poorly may lie in them having a more severe form of the illness. Likewise, people who never exercise very much may be that way because they are not in good health. Still, I think that there is enough overall evidence to support the role of exercise in the maintenance of good health. Doing it partly for cancer prevention can't hurt.