Breaking up prolonged periods of sitting with short bouts of physical activity may reduce the risk of cancer-related death, according to a study published in PLOS Medicine.

Researchers analyzed data from 91,292 UK Biobank participants who wore wrist accelerometers for seven days to objectively measure sedentary behavior and physical activity. Participants were followed for a median of 12.38 years to assess cancer incidence and mortality.

Sedentary behavior was categorized as prolonged sitting (≥30 minutes without interruption) or interrupted sitting, in which periods of sitting were broken up by movement. Each additional hour of prolonged sedentary behavior was associated with a 9% higher risk of overall cancer mortality, whereas each additional hour of interrupted sedentary behavior was associated with a 19% lower risk of cancer mortality.

Replacing prolonged sitting with physical activity was also associated with lower cancer mortality. Substituting 1 hour of prolonged sitting with light-intensity physical activity, such as walking or household chores, was associated with a 12% lower risk of cancer-related death. Replacing 30 minutes of prolonged sitting with moderate physical activity was associated with an 8% lower risk, while replacing 5 minutes of prolonged sitting with vigorous physical activity was associated with a 22% lower risk of cancer mortality.

Prolonged sedentary behavior was also associated with a higher incidence of overall cancer, obesity-related cancers, and type 2 diabetes-related cancers. Although the observational study cannot establish causality, the findings suggest that not only the total amount of sedentary time but also how sedentary time is accumulated, may be important for cancer risk. Reducing long, uninterrupted periods of sitting and replacing them with physical activity, even at light intensity, may represent a practical target for future interventions.