NEW YORK - Getting plenty of recreational activity may reduce women's risk of developing breast cancer after menopause, and exercise appears to have the most powerful preventive effect on the most aggressive type of tumour.
In a study, women who reported the highest level of recreational activity wereless likely to develop breast cancer than the least active women, Dr Aditya Bardia of the Mayo Clinic College of Medicine in Rochester, Minnesota and colleagues found.
In addition, women who exercised were less likely to develop breast tumours that carried oestrogen receptors but no receptors for progesterone. This type of tumour is generally more aggressive than those with other receptor configurations, Bardia's team notes in a report Archives of Internal Medicine.
Previous research on exercise and breast cancer risk has had mixed results, which may be because exercise may have different effects on the risk of developing different tumour types, the researchers note.
To investigate, the researchers looked at 36,363 women participating in the Iowa Women's Health Study. During the 18-year follow-up period, 2548 cases of breast cancer occurred.
Tumours carrying both oestrogen and progesterone receptors were most common, representing 71.1 per cent of the breast cancer cases, followed by tumours with oestrogen receptors but no progesterone receptors (13.5 per cent), tumours with neither type of receptor (13.1 per cent), or tumours with progesterone receptors only (2.3 per cent).
Overall, the researchers found, the most active women had a 14 per cent lower risk of breast cancer, while their risk of developing tumours carrying oestrogen receptors only was 33 per cent lower.
If other studies confirm this hypothesis, they add, "Physical activity would have a substantial public health effect on the prevention of this disease, along with its other positive health benefits."
Source: Archives of Internal Medicine, December 11/25, 2006.
