Sez the BBC:
Housework cuts breast cancer risk
The latest study looked at both pre- and post-menopausal women and a range of activities, including work, leisure and housework. …
Out of all of the activities, only housework significantly reduced the risk of both pre- and post-menopausal women getting the disease.
Housework cut breast cancer risk by 30% among the pre-menopausal women and 20% among the post-menopausal women. …
The explanation does make some sense:
The international authors said their results suggested that moderate forms of physical activity, such as housework, may be more important than less frequent but more intense recreational physical activity in reducing breast cancer risk.