Regular physical activity cuts breast cancer risk

London: Practising sport for more than anhour a day reduces the risk of developing breast cancer, and this applies to women of any age and any weight, according to a new study. Researchers found that compared with the least active women, those with the highest level of physical activity reduced their risk of breast cancer by 12 per cent.

Professor Mathieu Boniol, Research Director at the

International Prevention Research Institute, Lyon, France, reported the results of a meta-analysis of 37 studies published between 1987 and 2013, representing over four million women.

"These are all the studies looking at the relationship between physical exercise and breast cancer risk that have been published to date, so we are confident that the results of our analysis are robust," he said.

Although the results varied according to tumour type, the overall message was encouraging, researchers said. However, in women taking hormone replacement therapy (HRT), the protective effect of exercise seemed to be cancelled out.

But increased awareness of the side effects of HRT means that its use is decreasing in a number of countries, and this means that the beneficial effects of activity will most likely grow in the years to come, researchers said.

Physical activity is known to have a protective role in other cancers, as well as in disorders such as cardiovascular disease. Although the mechanisms for its effect are unclear, the results are largely independent of body mass index (BMI), so the effect must be due to more than weight control.

The age at which sporting activity starts also appears to be immaterial; the researchers found no indication that breast cancer risk would decrease only when physical activity started at a young age.