Sitting for Prolonged Periods May Increase Cancer Risk, Study Suggests

Modern lifestyles encouraging prolonged sitting are linked to an increased risk of cancer and cancer-related death, according to new research published in the journal PLOS Medicine. The study found that individuals who interrupted sedentary periods with physical activity experienced a lower likelihood of dying from cancer.

Researchers examined data from over 91,000 adults in the U.K. who wore wrist trackers to monitor their activity levels. Participants were followed for a median of over 12 years for cancer diagnoses and cancer-related deaths. The study categorized sedentary behavior into prolonged (over 30 minutes) and interrupted (less than 30 minutes, broken by movement).

Results showed that those with higher rates of prolonged sedentary behavior faced a greater risk of certain cancers, including breast, colorectal, esophageal, thyroid, and liver cancers, as well as a higher risk of cancer-related death.

Specifically, replacing sedentary time with physical activity yielded measurable benefits. Those who engaged in at least an hour of light-intensity physical activity, such as slow walking or household chores, had a 12% reduced risk of cancer-related death. Replacing 30 minutes of sitting with moderate activity, like a brisk walk, lowered the risk by 8%. Even replacing just five minutes of sedentary time with vigorous exercise showed a 22% decrease in cancer-related death risk.

"Just get up. That is the main message there," said Dr. Heidi Prather, founder and medical director of the Hospital for Special Surgery’s Lifestyle Medicine Program in New York, who was not affiliated with the study. "Obviously, we’re all tied to a computer or a car or something that keeps us inactive, but just interrupting that with any type of activity seems to have, per their data, some very impressive results. Not just cancer death, but even risk of developing cancer."

Movement helps reduce inflammation in the body, which is a contributing factor to cancer development. Prather noted that while genetics play a role in cancer risk, lifestyle factors such as diet, sleep, stress, and exercise account for approximately 40%. Sedentary behavior can also contribute to obesity, a known risk factor for several types of cancer.

The study authors acknowledged limitations, including that participants from the U.K. Biobank may have higher physical activity levels than the general population. Additionally, the specific activities during sedentary periods were not detailed.

Experts emphasize that regular exercise is beneficial, but it does not entirely negate the risks of prolonged sitting. Simple actions like parking further away, taking the stairs, or getting off public transport a stop early can contribute to overall movement. The key takeaway is to break up long periods of inactivity, as prolonged sedentary behavior can be as risky as not exercising at all, according to Prather. "We were meant to move... we were not meant to sit."