Taking regular exercise and not being a couch potato are highly likely to cut the chance of breast cancer, experts have said.
A new study published in the British Journal of Sports Medicine found “strong evidence that greater levels of physical activity and less sedentary time are likely to reduce breast cancer risk, with results generally consistent across breast cancer subtypes”.
Experts behind the research suggested there was now a clear cause-and-effect relationship between exercise and reducing breast cancer risk.
Using a genetic prediction technique called Mendelian randomisation in the study, experts said they were able to strengthen the previous evidence that exercising cuts cancer risk.
For the new research, experts included data from 130,957 women of European ancestry – of whom 69,838 had tumours that had begun to spread; 6,667 who had tumours that had not yet done so and a comparison group of 54,452 women without breast cancer.
Their results showed that overall activity was associated with about a 40% lower risk of breast cancer, while vigorous activity (on three or more days a week) was associated with a similar reduced risk of pre or perimenopausal breast cancer.
Being sedentary, on the other hand, was associated with a higher risk of some types of breast cancer.
The team, including experts from the University of Bristol, concluded: “Our study provides strong evidence that greater overall physical activity, greater vigorous activity, and lower sedentary time are likely to reduce breast cancer risk.
“More widespread adoption of active lifestyles may reduce the burden from the most common cancer in women.”
There are about 55,900 new breast cancer cases in the UK every year, making it the country’s most common cancer.
Drinking too much alcohol, being overweight or obese and being older all increase the risk of breast cancer.
Dr Kotryna Temcinaite, senior research communications manager at Breast Cancer Now, said: “One woman is diagnosed with breast cancer in the UK every 10 minutes and if nothing changes this will rise to one woman every eight minutes in the next 10 years, so we urgently need to find new ways to prevent people from developing this devastating disease.
“While many factors can affect how likely someone is to be diagnosed, we already know that being physically active is linked to a lower chance of developing breast cancer.
“By looking at people who may be genetically predisposed to having different physical activity levels, this innovative study further strengthens existing evidence of the importance of reducing the time we spend sitting and increasing the amount of time we spend moving to lower breast cancer risk.
“Maintaining a healthy weight, limiting alcohol intake and being as active as possible, can all help reduce the risk of developing the disease.
“This research highlights how vital it is that we support people to start making small, healthy lifestyle changes that can positively impact their health and help lower their risk of breast cancer.”
Dr Helen Croker, head of research interpretation at World Cancer Research Fund, said: “We welcome this new research which strengthens previous findings that physical activity reduces breast cancer risk by showing that the relationship is causal.
“Being physically active, along with avoiding drinking alcohol and excess weight gain across life, can all contribute to lowering the chances of developing breast cancer.”