A study published in PLOS Medicine by Frederick Ho from the University of Glasgow (UK) and his colleagues reveals that each additional hour of prolonged, uninterrupted sedentary behavior during the day is linked to a 9% higher risk of cancer-related death.
Earlier research has indicated that increasing the total amount of time spent in a seated position—such as sitting, reclining, or lying down throughout the day—is associated with poorer health outcomes. However, most guidelines on managing sedentary behavior focus on the overall time spent sitting, rather than whether this time is accumulated through many short intervals or fewer extended periods.
In this new study, scientists analyzed data from 91,292 participants in the UK Biobank, who wore activity monitors for seven days and were then followed for an average of 12.38 years. Activity was categorized into prolonged sedentary behavior (periods lasting at least 30 minutes, with at least 90% of time spent sitting), interrupted sedentary behavior (lasting less than 30 minutes or interrupted by more than 10% of time spent outside a seated position), and varying levels of physical activity.
Prolonged sedentary behavior was associated with a higher risk of cancer mortality, overall cancer incidence, obesity-related cancers (such as cancers of the esophagus, liver, kidneys, pancreas, colon, breast, ovaries, and thyroid), as well as cancers linked to type 2 diabetes.
In contrast, interrupted sedentary behavior showed the opposite pattern and was linked to a lower risk across all these measures. Replacing one hour per day of prolonged sedentary behavior with light physical activity was associated with a 12% reduction in the risk of cancer death.
Since this study was conducted on a single cohort of volunteers from the UK Biobank, who are known to have a health-conscious bias and higher levels of physical activity than the general UK population, the findings may not apply to other groups and do not establish causation. Additionally, the researchers lacked data on the context of sedentary behavior, such as whether it occurred during work or while driving.
“Our findings suggest that the health impact of a sedentary lifestyle may depend not only on the total time spent sitting but also on whether that time is accumulated in long stretches or broken up by physical activity,” the authors state. “This pattern is biologically plausible: experimental studies have shown that interrupting prolonged sitting with short periods of activity can improve metabolic responses compared to continuous sitting.”
“Current health guidelines largely emphasize moderate or vigorous exercise, but our results indicate that light physical activity should not be overlooked. Moving forward, clinical research will help us move beyond general recommendations and develop personalized strategies to reduce time spent sitting,” they concluded.
About the Author
