Prolonged sitting linked to higher cancer risk and mortality

Researchers found that the health effects of sedentary behavior depend not only on the total amount of time spent sitting but also on how long periods of uninterrupted sitting last. The study, published in PLOS Medicine, examined data from more than 91,000 participants in the UK Biobank who had no history of cancer at the start of the study.

Each participant wore an activity-monitoring device for seven days, and the researchers followed their health outcomes for about 12 years.

The findings showed that each additional hour per day spent in prolonged periods of sitting was associated with a 9% higher risk of dying from cancer and a 3% higher risk of developing cancer.

By contrast, breaking up sitting periods with movement was associated with better outcomes. Each hour of intermittent inactivity was linked to an 18% lower risk of cancer-related death and a 6% lower overall risk of developing cancer.

The researchers also found that replacing one hour of prolonged sitting each day with light physical activity was associated with a 12% lower risk of cancer-related death and a 6% lower risk of developing cancer.

Frederick Ho, an epidemiologist at the University of Glasgow and the study's lead author, said health guidelines typically emphasize moderate- or vigorous-intensity exercise. However, the findings suggest that light physical activity also matters, noting that briefly interrupting long periods of sitting with a short walk may be beneficial.

The study does not establish that prolonged sitting directly causes cancer. As an observational study, it identifies associations between sitting patterns and health outcomes but cannot establish a causal relationship.

The researchers said the findings add to growing evidence of the importance of reducing sedentary behavior and suggest that incorporating short periods of movement throughout the day could be a simple and beneficial step, particularly for people who have to sit for many hours.