TAKING part in sport for more than an hour a day reduces women’s risk of developing breast cancer, research shows.
The study, presented at the European Breast Cancer Conference in Glasgow, found that the risk was reduced regardless of the age or weight of the women taking part in physical activity.
The study found that compared with the least active women, those with the highest levels of exercise reduced their risk of breast cancer by 11 per cent.
The researchers said that the benefits increased the more exercise that women did. But any benefits were cancelled out if they were using hormone replacement therapy (HRT), which has been shown to increase the risks of breast cancer.
Campaigners welcomed the findings and said women could make a difference to their risk of breast cancer even with small changes to their physical routine.
The latest study, carried out at the International Prevention Research Institute in Lyon, France, collected together the results of 37 pieces of research carried out between 1987 and 2013 looking at links between exercise and breast cancer risk.
These studies included more than 4.2 million women, with 113,059 suffering breast cancer.
The research, led by Professor Mathieu Boniol, focussed on those taking part in more vigorous exercise, which was the easiest to measure in the different studies, although other evidence suggests more sedate activity can also help reduce risks.
They concluded that there was an 11 per cent reduced risk of developing breast cancer in those doing the highest level of activity compared to those doing the least.
Prof Boniol said: “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.”
However the research discovered that the protective effects of exercise were cancelled out in those using HRT.
With increased awareness of the side-effects of HRT meaning its use is decreasing in many countries, it could mean that the beneficial effects of exercise could grow in the coming years, the researchers said.
But one positive finding from the research was that exercise reduced the risk of breast cancer regardless of women’s weight, meaning even those who were overweight also seemed to benefit from taking part in physical activity.
And Prof Boniol said those who wished to do more exercise reduced their risk of cancer further.
“There is a dose-related response,” he said.
“Anyone who increases their physical activity will see a benefit.”
Taking part in physical activity is known to have a protective effect in other types of cancer, including bowel cancer, as well as diseases such as heart disease.
But how it has this effect is still unclear, as studies take into account patients’ body mass index (BMI) meaning it must be due to more than weight control alone.
Prof Boniol said: “Adding breast cancer, including the aggressive types, to the list of diseases that can be prevented by physical activity should encourage the development of cities that foster sport by becoming bike and walk-friendly, the creation of new sports facilities and the promotion of exercise through education campaigns.”
Dr Hilary Dobson, chair of the conference’s organising committee and lead clinician at the West of Scotland Cancer Advisory Network, said: “These findings are important for all women, irrespective of their age and weight.
“While the mechanism for the potentially protective effect of physical activity remains unclear, the analysis provides women with a real impetus to increase their physical activity even by modest increments.”
James Jopling, director for Scotland at charity Breakthrough Breast Cancer, said the findings were “exciting”.
“Breakthrough Breast Cancer recently looked into all the best studies on physical activity and breast cancer with experts across the world, and we also found that there is good evidence that women can reduce their risk of breast cancer by being regularly active,” he said,
“Even better, moderate physical activity counts, which can be things like gardening, housework or a brisk walk – so there are many ways to fit the needed physical activity into your day to day life.”