Study links each extra hour of prolonged sitting to 10% higher cancer death risk, finds light activity cuts risk

People who accumulated the most time in prolonged sedentary bouts faced higher risks of cancer mortality, overall cancer incidence, obesity-related cancers and type 2 diabetes-related cancers, Euronews reported. The study, published in PLOS Medicine and drawing on wearable data from roughly 90,000 UK Biobank volunteers followed for a median of 12 years, found that each additional hour of prolonged sedentary behavior raised the risk of cancer death by 10%.

Replacing one hour of sitting with light physical activity such as walking or household tasks reduced the risk of cancer death by 12%, the same analysis showed.

Replacing just five minutes a day with vigorous exercise was associated with a 22% lower risk of cancer death. The authors defined prolonged sedentary behavior as periods of at least 30 minutes in which people barely moved for at least 90% of the time. Total sedentary time itself was also tied to elevated relative risk of cancer incidence and mortality.

“Our findings suggest that the health effects of sedentary behaviour may depend not only on total sedentary time, but also on whether that time is accumulated in prolonged bouts or interrupted by activity,” the authors stated. They noted that prior experimental work has shown interrupting prolonged sitting with short activity bouts improves metabolic responses.

“Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement shouldn't be ignored,” the authors wrote.

Sedentary behavior accounts for around 55% of waking time in both children and adults based on self-reported data. At the 2018 World Health Assembly, countries set a target of a 15% reduction in physical inactivity by 2030 compared with 2010 levels. The World Health Organization warned in 2024 that inactivity could rise to 35% by 2030 if trends continue.