A study tracking more than 90,000 people over a decade has found that sitting for longer than half an hour at a time each day raises the risk of dying from cancer. The research, published in Plos Medicine, suggests that every additional hour of continuous inactivity increases the risk. However, breaking up prolonged sedentary behaviour with bursts of physical activity, even light movement such as ironing or walking, could help reduce the risk.
Key Findings on Sedentary Behaviour and Cancer Risk
Researchers from the University of Glasgow analysed data from wearable devices worn by over 91,000 UK Biobank participants, followed for an average of 12 years. Prolonged inactivity lasting more than 30 minutes was associated with higher cancer risks. Each additional hour of prolonged inactivity per day was linked to a 10% increase in risk of cancer death.
Dr Frederick Ho, lead author of the study, said: “What our data shows is that sitting for more than 30 minutes at a time is particularly linked to a higher risk of cancer. The good news is that breaking up your sitting time with something as simple as a short walk could be protective.”
Benefits of Replacing Sedentary Time with Activity
Replacing long spells of inactivity with movement appeared to reduce the risk. Substituting one hour of sedentary behaviour each day with light physical activity, such as ironing or washing up, was associated with a 12% lower risk of cancer death. Replacing 30 minutes of inactivity with 30 minutes of moderate physical activity, like walking at an average pace, was linked to an 8% lower risk. The risk was 22% lower when five minutes of inactivity was replaced with five minutes of vigorous physical activity each day.
Dr Ho added: “Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement should not be ignored. Moving forward, clinical trials will help us move beyond blanket advice and develop personalised strategies for breaking up sitting time.”
Limitations and Expert Commentary
The researchers noted limitations, including that the study was observational and could not prove causation. Prof Kevin McConway, an emeritus professor of applied statistics at the Open University, who was not involved in the research, said the findings were interesting but further research would be needed.
The study focused on the health effects of prolonged sedentary behaviour on a daily basis, highlighting that even light activities such as slow walking and housework could help reduce cancer risks.
