At the moment, we don’t know why some women will develop breast cancer, but others won't. So, in 2004 we set up the Generations Study, a project following over 100,000 women in the UK for 40 years. Having a large, multi-decade study like this allows researchers to gather enough data to uncover as many factors linked to breast cancer as possible.
Dr Michael Jones from the Institute of Cancer Research, London and his team analysed data from 547,000 women from 19 studies, including the Generations Study. They used data collected from questionnaires and looked at the amount of physical activity women reported doing in their free time. This included sports, exercise and recreational walking.
The researchers found that women who were in the top 10% of most active participants were 10% less likely to develop breast cancer before the menopause. This was compared to people who ranked in the bottom 10% of doing physical activity. Their analysis took into account other breast cancer risk factors and lifestyle behaviours. This included things like BMI, family history, and smoking.
Michael and his team also found that there wasn't a specific amount of physical activity that women needed to do to see benefits. But the more time they spent doing physical activity outside of work, the lower their chances of getting breast cancer.
Scientists don’t fully understand how exercise affects how likely someone is to get breast cancer. But previous research has shown that exercise can lower sex hormones like oestrogen and testosterone which have been linked to an increased risk of breast cancer. Physical activity can also lower someone’s levels of insulin and growth hormone which can help breast cancer to grow. Additionally, exercise decreases inflammation, which is linked to cancer growing and spreading.
Dr Simon Vincent, director of research, support and influencing at Breast Cancer Now, said: “Although breast cancer is more common in older women, 6,000 women aged 45 or younger are given the devastating news that they have breast cancer each year in the UK. Breast cancers in younger women tend to be more aggressive and diagnosed at a later stage, so we urgently need to find new ways to prevent people from developing the disease. There’s no single cause of breast cancer as it results from a combination of the way we live our lives, our genes and our environment. But while we can’t predict who will get breast cancer, there are some things people can do to lower their chances of getting it. This research highlights how vital it is that we support women to start making small, healthy lifestyle changes that can positively impact their health and help lower their risk of breast cancer."
The study was published in the Journal of Clinical Oncology and funded by Breast Cancer Now. The complete published study can be found here.
Read the full press release with Breast Cancer Now here.