Data from more than 91,000 participants in the UK Biobank who wore activity monitors for seven days revealed an association between prolonged sedentary behavior and the risk of cancer death.

Each additional hour of prolonged, uninterrupted sedentary behavior in a person’s day is associated with a 9% higher risk of cancer death, according to a study published July 2nd in the open access journal PLOS Medicine by Frederick Ho of the University of Glasgow, UK, and colleagues.

Previous studies have shown that spending more total time on sedentary behavior, such as sitting, reclining or lying down while awake, is linked to poorer health outcomes. However, 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.

In the new study, researchers analyzed data from 91,292 UK Biobank participants who had worn activity monitors for 7 days and were followed for a median of 12.38 years afterward. 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 (HR 1.09; 95% CI 1.06, 1.11), 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 (HR 0.88; 95% CI 0.79, 0.99).

As a single-cohort study of UK Biobank volunteers, who have known health volunteer bias and higher physical activity levels than the general UK population, the findings may not be generalizable and do not prove causality. The researchers also had no data on the context of sedentary behavior, such as whether it was during work or driving.

“Our findings suggest health effects depend on whether sedentary time occurs in prolonged bouts or is interrupted by activity,” the researchers explained. This approach is biologically plausible since research demonstrates that breaking up prolonged sitting with activity bouts improves metabolic responses.

The authors emphasized that “light movement shouldn’t be ignored” and that future clinical trials should help develop personalized strategies for reducing continuous sitting periods.

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Citation: Zhou Z, Trost SG, Ryde GC, Parra-Soto S, Fang Z, Xu C, et al. (2026) Accelerometry-measured prolonged and interrupted sedentary behavior and cancer incidence and mortality: A cohort study of 91,292 UK Biobank participants.
Journal: PLOS Medicine 23(7): e1004767
DOI: 10.1371/journal.pmed.1004767

Source: EurekAlert