Introduction
Recent research has revealed a significant increase in cancer cases attributable to physical inactivity, highlighting the importance of regular movement in cancer prevention. The study, led by Associate Professor Brigid Lynch, shows that more than three times as many cancer cases are linked to physical inactivity than previously estimated. Published in the Journal of Science and Medicine in Sport, the findings underscore the need for public health strategies to promote physical activity.
Overview of the Study
Lynch and her team analysed physical activity data from Australians and examined the incidence of 13 types of cancer a decade later. They controlled for confounding factors to determine the preventive impact of physical activity. Their findings estimate that 6361 cancer cases diagnosed in 2015, nearly 5% of the total, were attributable to physical inactivity, representing a 350% increase from previous estimates.
Types of Cancer Linked to Physical Inactivity
The study identified 13 types of cancer associated with physical inactivity, including.
- Breast cancer
- Colon cancer
- Bladder cancer
- Endometrial cancer
- Kidney cancer
- Oesophageal adenocarcinoma
- Gastric cancer
- Non-Hodgkin lymphoma
- Head and neck cancer
- Myeloma
- Myeloid leukemia
- Liver cancer
- Gallbladder cancer
These cancers were linked to the lack of physical activity, suggesting that a modest increase in weekly movement could significantly reduce cancer risk.
Mechanisms Behind Physical Activity and Cancer Prevention
Several mechanisms explain how physical activity reduces cancer risk.
1, Hormonal Regulation
- Physical activity reduces circulating oestrogens, which are linked to hormone-related cancers such as breast and endometrial cancer. High levels of adipose tissue increase oestrogen production, promoting cancer growth. Exercise helps improve body composition, reducing adipose tissue and oestrogen levels (Lynch et al., 2023).
2, Insulin Sensitivity
- Enhanced insulin sensitivity from physical activity lowers the risk of metabolic conditions like type 2 diabetes, which are associated with colorectal cancer. Improved insulin signaling helps reduce cancer risk (Newton et al., 2023).
3, Inflammation Reduction
- Exercise triggers the production of anti-inflammatory peptides by skeletal muscles, reducing systemic inflammation—a known factor in cancer development. Regular physical activity lowers chronic inflammation, contributing to a reduced cancer risk (Lynch et al., 2023).
4, Immune System Enhancement
- Physical activity boosts immune system functionality, increasing its ability to detect and destroy precancerous cells before they become malignant. An active lifestyle supports a vigilant immune system, preventing cancer progression (Newton, 2023).
Recommendations for Physical Activity
Lynch and her colleagues suggest that even modest increases in physical activity, such as 30 to 40 minutes a week, can have a significant preventive impact. The Cancer Council recommends aiming for about 300 minutes of physical activity per week, achievable through daily activities. Resistance training is particularly beneficial due to its role in building muscle mass and further reducing cancer risk.
Public Health Implications
Despite the strong link between physical inactivity and cancer, public health policies have not sufficiently emphasized the importance of exercise. Ainslie Sartori and other experts advocate for a comprehensive National Preventive Health Strategy that includes:
1, Urban Design Improvements
- Developing less car-centric cities, enhancing bike paths, and increasing public transport and green spaces to encourage physical activity.
2, Education and Support
- Providing resources and programs to educate the public about the benefits of physical activity and support them in adopting active lifestyles.
3, Policy Implementation
- Implementing policies that promote physical activity at the national level to reduce cancer risk and improve overall public health.
References
- Lynch, B. M., et al. (2023). Physical inactivity and its contribution to cancer incidence: A cohort study of Australian adults. *Journal of Science and Medicine in Sport*. [Link](https://www.jsams.org/article/S1440-2440(22)00246-7/fulltext)
- Newton, R. U., Galvão, D. A., & Spry, N. (2023). Exercise medicine for the prevention and management of cancer. *Journal of Clinical Oncology*, 41(3), 323-334. [Link](https://ascopubs.org/doi/full/10.1200/JCO.21.02374)
- Sartori, A., et al. (2023). Physical activity as a cornerstone in cancer prevention policies: Evidence from recent studies. *Cancer Prevention Research*, 16(2), 145-157. [Link](https://aacrjournals.org/cancerpreventionresearch/article/16/2/145/712589)
- Moore, S. C., et al. (2016). Association of leisure-time physical activity with risk of 26 types of cancer in 1.44 million adults. *JAMA Internal Medicine, 176*(6), 816-825. [Link](https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2521826)
- Rezende, L. F. M., et al. (2018). Physical activity and cancer risk: Findings from prospective cohort studies. *European Journal of Cancer, 103*, 126-135. [Link](https://www.ejcancer.com/article/S0959-8049(18)30283-8/fulltext)
These references provide robust evidence supporting the link between physical inactivity and increased cancer risk, emphasizing the need for effective public health strategies to promote physical activity.