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Is there a link between physical activity and breast cancer?  

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Did you know that some 27% of Quebecers are considered active in their leisure time? However, the proportion of inactive people in the 15-64 age group rose significantly from 2014 to 2021.

This trend might make one think not only about the importance of physical activity in our daily lives, but about the impact that this healthy lifestyle habit may have on preventing breast cancer.

Everything you need to know about physical activity

The World Health Organization (WHO) defines physical activity as any bodily movement produced by skeletal muscles that requires energy expenditure. Physical activity refers to all movement, including during leisure time, for transport to get to and from places, or as part of a person’s work or domestic activities.

It is recommended that Canadians practise at least 150 minutes of moderate- to vigorous-intensity physical activity weekly. Moderate intensity is defined as reaching 50-70% of your maximum heart rate. It is considered intense when 70-85% of this rate is reached.

The type of activity and the time needed to reach these intensities varies from person to person. You may also find that your physical activity is below these recommended thresholds. This is known as physical inactivity, in other words a lack of regular physical activity.

It is also important to distinguish between being physically inactive and being sedentary, meaning spending awake time in a sitting or lying position. A physically active person can still be considered sedentary if they spend most of their awake time sitting or lying down (e.g., working at a desk, sitting in a car, watching television, etc.). 

What is the connection between physical activity and breast cancer?

We know that physical activity is one way of lowering the risk of breast cancer. The aim of the ComPARe (Canadian Population-Attributable Risk of Cancer) study was to gain a better understanding of the risks associated with cancer in the Canadian population. According to the study, 4 out of 10 cancers could be prevented by changes to daily lifestyle habits, including boosting physical activity.

This study estimated that physical inactivity contributed to around 7.4% of breast cancers diagnosed in Canada in 2015. It is estimated that 1 in 4 breast cancers could be prevented by adopting healthy lifestyle habits, including a higher level of physical activity.

Several studies have shown a 10 to 25% reduction in the incidence of the disease in women who take part in regular physical activity, compared with those who are inactive. 

Remember, the World Cancer Research Fund International (WCRF) recommends 150 minutes of moderate or 75 minutes of vigorous physical activity weekly. It is also important to remember to follow the other recommendations for preventing breast cancer (e.g., alcohol consumption, eating a healthy, varied diet, etc.).

How does physical activity help reduce the risk of breast cancer?

The underlying reasons explaining the effect of physical activity on the risk of breast cancer are still poorly understood. However, the WCRF does explain the benefits of physical activity in combatting breast cancer. 

Physical activity reduces the level of estrogen circulating in the bloodstream. Exposure to estrogens has an impact on the risk of developing breast cancer. This is explained by their effect on breast cell growth.

Physical activity also helps to strengthen the immune system and combat inflammation, thereby creating an environment that is less conducive to the formation of breast tumours. As a result, the risk of breast cancer may be reduced. 

Finally, physical activity is thought to contribute to limiting the risk of the disease by helping to maintain a healthy weight and reduce body fat. Obesity is associated with a higher risk of breast cancer, particularly in post-menopausal women. Although there are many factors that affect weight gain, physical activity is one way of limiting it.

What kinds of physical activity are recommended to prevent breast cancer?

Many people wonder if a specific physical activity is better for preventing breast cancer.

Generally speaking, the most important thing is to move every day. Whatever the physical activity, the key is to find one that you enjoy doing and that is easy to incorporate into your daily routine.

As previously mentioned, 150 minutes of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise per week is recommended. The impact is even greater when the activity is done on a regular basis. 

People also sometimes wonder whether walking is a good way of preventing breast cancer. Absolutely! Walking is an excellent way of incorporating physical activity into your daily routine. It can be of moderate intensity and is a good way to introduce newcomers to physical activity.

Walking also reduces the amount of sedentary time spent during the day. It is important to be physically active to reduce your risk of breast cancer but also to limit sedentary time (time spent sitting or lying down during the day).

Finally, keep in mind that other activities such as dancing, gardening or housework also contribute to your daily active time. All movement is beneficial!


References

  • Habitudes de vie et comportements: faits saillants. Institution de la statistique du Québec, Enquête québécoise sur la santé de la population, 2020 – 2021. Institut de la statistique du Québec. 16 mai 2023.
  • Risque attribuable du cancer du Canada: ComPARe (Canadian Population Attributable Risk of Cancer, Risque attribuable du cancer chez la population canadienne). Attributable cancer case(s) due to physical inactivity in Canada for all ages 2015, consultée à Cancer data – ComPARe, 2 avril 2024.
  • Moore SC et al. Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults. JAMA Intern Med. 2016 Jun 1
  • Lynch BM et al. Physical activity and breast cancer prevention. Recent Results Cancer Res. 2011
  • Ortega MA et al. Physical Activity as an Imperative Support in Breast Cancer Management. Cancers (Basel). 2020 Dec 28;13
  • WCRF/AICR. Diet, nutrition, physical activity and breast cancer. WCRF/AICR Report. Revised 2018
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  • Timmins IR et al. International Pooled Analysis of Leisure-Time Physical Activity and Premenopausal Breast Cancer in Women From 19 Cohorts. J Clin Oncol. 2024 Mar 10;42(8):927-939. Epub 2023 Dec 11
  • Hong BS, Lee KP. A systematic review of the biological mechanisms linking physical activity and breast cancer. Phys Act Nutr. 2020 Sep;24(3):25-31. Epub 2020
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