Prolonged sitting linked to higher risk of dying from cancer

By Stephen Beech

A couch potato lifestyle raises the risk of dying from cancer, warns new research.

People who spend prolonged periods of time sitting or lying down are more likely to die from the disease, according to the findings.

The research shows that for each additional hour of prolonged, uninterrupted "sedentary behavior"—such as sitting, reclining or lying down while awake—in a person's day is associated with a 9% higher risk of dying from cancer.

The international study, led by Glasgow University scientists, involved more than 91,000 British participants wearing activity monitors.

Previous studies have shown that spending more total time spent in sedentary mode is linked to poorer health outcomes.

But most sedentary behavior guidelines focus on total time spent sedentary, rather than whether that time is accumulated in many short intervals or fewer prolonged intervals.

For the new study, researchers analyzed data from 91,292 UK Biobank participants who had worn activity monitors for seven days and were followed for an average of 12.38 years.

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Activity was categorized as either "prolonged sedentary"—bouts of at least 30 minutes with at least 90% of time sedentary; "interrupted sedentary behavior" which lasted less than 30 minutes or was broken up with more than 10% non-sedentary time; or varying degrees of physical activity.

Prolonged sedentary behavior was associated with a higher risk of cancer mortality, overall cancer incidence, obesity-related cancers—such as esophageal, liver, kidney, pancreatic, colorectal, breast, ovarian and thyroid cancers, and type 2 diabetes-related cancers.

Interrupted sedentary behavior showed the opposite pattern, associated with lower risk across all outcomes.

Replacing one hour per day of prolonged sedentary behavior with light physical activity was associated with a 12% lower risk of cancer death, according to the study published in the journal PLOS Medicine.

Study co-author Frederick Ho said: "Our findings suggest that the health effects of sedentary behavior may depend not only on total sedentary time, but also on whether that time is accumulated in prolonged bouts or interrupted by activity.

"This pattern is biologically plausible: experimental studies have shown that interrupting prolonged sitting with short bouts of activity can improve metabolic responses compared with uninterrupted sitting."

Ho, of the University of Glasgow's School of Health & Wellbeing, added: "Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement shouldn't be ignored.

"Moving forward, clinical trials will help us move beyond blanket advice and develop personalized strategies for breaking up sitting time."