Sedentary Lifestyle and Cancer Risk: A Concerning Connection
How a sedentary lifestyle can increase the risk of developing cancer
Correlation between Sedentary Life and Cancer
A 2014 meta-analysis examined data from over 68,000 cancer cases and found that prolonged sedentary behaviors, such as watching TV or sitting for work, are associated with an increased risk of colon, endometrial, and lung cancer. An 8% and 10% increase in the risk of colon and endometrial cancer, respectively, was observed for every additional two hours of sedentary time per day. This positive association between sedentary behavior and cancer is believed to be caused by various factors, including obesity, chronic low-grade inflammation, insulin resistance, and vitamin D deficiency.
The Impact of Obesity and Vitamin D Deficiency
Obesity, strongly linked to lack of physical activity, can cause chronic inflammation and DNA damage, leading to cancer. Obesity can also lead to elevated insulin levels, which can promote cancer progression. Additionally, a sedentary lifestyle can result in vitamin D deficiency, essential for calcium and phosphorus regulation, and its deficiency has been linked to an increased risk of colon and breast cancer.
Physical Activity and Cancer Prevention
On the other hand, physical activity has been associated with a reduced risk of death from colon and prostate cancer. Epidemiological studies suggest that physical activity after a diagnosis of colon cancer is associated with a 30% lower risk of colon cancer death and a 38% lower risk of death from any cause. For prostate cancer, physical activity is linked to a 33% lower risk of prostate cancer death and a 45% lower risk of death from any cause.
Research and Recommendations
Clinical trials provide the strongest evidence of the link between physical activity and reducing the risk of cancer, as they eliminate bias related to pre-existing diseases and physical inactivity. To confirm observational evidence and determine the extent of the effect, numerous large clinical trials are currently underway examining physical activity and/or exercise interventions in cancer patients and survivors. These include the Breast Cancer Weight Loss (BWEL) trial for newly diagnosed breast cancer patients, the CHALLENGE trial for colon cancer patients who have completed chemotherapy, and the INTERVAL-GAP4 trial for men with metastatic castration-resistant prostate cancer. These studies aim to answer open questions about various aspects of physical activity and cancer research, such as the mechanisms through which physical activity reduces the risk of cancer, the optimal timing in life, intensity, duration, and/or frequency of physical activity needed to reduce the risk of cancer, both overall and for specific sites, and whether sedentary behavior is associated with an increased risk of cancer.