I ran across this story study linking breast cancer protection to housework while browsing Scienceblogs briefly over the break (GrrlScientist mentioned it here), but hadn’t had a chance until now to read through the actual publication. As usual, I’m late; Orac has a good overview, as well as some comments made by other bloggers railing against “feminism” and how this study proves that feminist philosophy kills women.
First, here’s how the BBC story describes it:
Women who exercise by doing the housework can reduce their risk of breast cancer, a study suggests.
The research on more than 200,000 women from nine European countries found doing household chores was far more cancer protective than playing sport.
Dusting, mopping and vacuuming was also better than having a physical job.
The women in the Cancer Research UK-funded study spent an average of 16 to 17 hours a week cooking, cleaning and doing the washing.
First, a bit about the actual paper. This was a giant study, pulling in data collected from over 200,000 women in several different European countries. This is both good and bad from an epidemiological point of view. Large numbers are a good thing, as it generally increases the ability of your study to find actual correlations. However, because these were pulled in from a variety of sites, the uniformity tends to decrease, as is evident by the fact that women from Norway and some from Sweden were excluded due to lack of information on physical activity. Data on activity was also self-reported rather than actively measured, so these are all estimates and subject to various biases and inaccuracies. These can cancel each other out (one woman may slightly over-report, another may under-report) and the questionnaires have already been validated in other studies, but one still must remember that the results of the analysis are only as good as the data put in, and these kinds of questionnaires are often difficult. Intensity of activity also wasn’t directly asked; rather, they assigned housework (and exercise) to levels based on type of activity (stair climbing versus gardening, for example)–again introducing some imprecision into the measurements. Each woman was then assigned an “activity index,” and the data was run in a multivariate model to control for potential confounders (age at menarche, number of births, current contraceptive or HRT use [but nothing about past use, as far as I can see], etc.)
Sooo, the methods certainly aren’t too bad, but they’re not exactly rock-solid either, and they weren’t designed specifically to address the question at hand. Additionally, as they note in their discussion, they only have data on physical activity from the previous year. Do these adequately reflect the risk over the life of the woman? My time spent on housework has certainly varied as kids have been born, pets have been attained, houses have changed size, etc.
Finally, despite the rantings of some of the “oooh, feminism and working outside the home is so bad, see, it kills you!” crowd, I think they’re missing an obvious point: many of us who work outside of the home *still* spend a significant part of our time on housework. Indeed, the average time spent per week in the cohort–be they women who worked outside the home or not–was 16-17 hours per week. Is it less than our mothers, our grandmothers? Probably, for many of us at least. But I’ll wager that even stay-at-home moms also spend less time on housework than their grandmothers, due not to the “evils of feminism” or any such nonsense, but simply to modern technology. Therefore, it’s equally stupid to say that dishwashers and vacuums “cause” breast cancer as it is to say that “feminism” does, especially when such a notion isn’t even supported by the study they’re trying to cite.