Study shows physical inactivity triples cancer risk

Reinforcing the importance of creating environments that support and promote exercise in Australia, newly released research has suggested that more than three times as many cancer cases are attributable to physical inactivity than previously thought.

The research led by the Cancer Council and funded by the Victorian Government through the Victorian Cancer Agency, quantifies the proportion of cancers attributable to physical inactivity - reflecting that more cancer types, including breast, colon, bladder, endometrial, kidney, oesophageal adenocarcinoma, gastric, non-Hodgkin lymphoma, head and neck, myeloma, myeloid leukaemia, liver, and gallbladder, are now linked to physical inactivity.

Published in the Journal of Science and Medicine in Sport, it estimates that of 6,361 of the cancers observed in 2015 were attributable to physical inactivity, representing 4.8% of all cancers diagnosed - a 350% increase from the previous estimation that 1,814 (1.6% of incident cancers) were attributable to physical inactivity in Australia in 2010.

Associate Professor Brigid Lynch, senior author of the paper, saw evolving evidence that physical inactivity was associated with at least 13 types of cancer - not just three types, as researchers once believed - and wanted to update the estimates based on Australian activity levels and cancer rates.

The research goes on to suggest that more than 2,500 cancer cases (1.9% of all cancers) could have been prevented in 2015 if Australian adults had increased their physical activity by a modest amount (around 40 minutes per week) a decade earlier.

Advising that the findings provide a contemporary understanding of the cancer burden due to physical inactivity, Associate Professor Lynch explained “we now know being physically active reduces the risk of 13 types of cancer.

“This new research highlights the number of individual cancer diagnoses that could have been prevented if Australians were better supported to integrate regular physical activity into their day.”

Ainslie Sartori, Deputy Chair of Cancer Councils Nutrition, Alcohol and Physical Activity Committee says these findings are essential to improving how physical activity is considered in cancer prevention policies, noting “Australia is a nation proud of its health system, yet we don’t have a physical activity plan or coordinated national physical activity strategy. Combined with changes in food supply, eating behaviours, a rise in convenience and ultra-processed foods, we are living in environments that do not promote healthy lifestyles.

“We want to ensure there are systems and environments in place for all Australians to develop strong physical activity habits that they can carry on, reducing their risk of developing cancer later in life.”

While any type of activity reduces risk, the significance of muscle mass in a cancer suppressing environment may make regular resistance training particularly powerful, says Professor Rob Newton, the Deputy Director of Edith Cowan University’s Exercise Medicine Research Institute.

Professor Newton explains that physical activity has a “huge influence” over the functionality of the immune system, noting “when you have a more effective, more surveillant system that can identify and destroy those precancerous cells, they never progress to a malignancy.”

However, he acknowledges that there has been little emphasis on physical activity in cancer prevention, adding “this is something we really need to address ... we can’t keep throwing drugs at these things.”

Currently, there is no national physical activity plan to inform governments about creating systems that promote being active, like less car-centric cities, improved bike paths, more public transport and access to green spaces.

To address this, Sartori and Associate Professor Lynch are urging the government to implement the National Preventive Health Strategy and National Obesity Strategy which recommends a physical activity policy, as well as urban design, education, and support to encourage and enable people to increase their physical activity and live longer and healthier lives.

Click here to view the paper in the Journal of Science and Medicine in Sport.