Prolonged Sedentary Behavior May Increase Cancer Risk

Excessive sedentary behavior is a risk factor for cardiovascular disease, type 2 diabetes, obesity, and all-cause mortality. 

A new study has found that how time spent in sedentary behavior accumulates is also important, with prolonged sedentary behavior associated with increased cancer risk. 

Different sedentary behavior patterns 

It is estimated that we spend around 55% of our waking time sedentary. Sedentary behaviors are activities that require low energy expenditure and are performed while sitting, reclining, or lying down, like watching TV, reading a book, or working at a desk. 

More time spent in a sedentary state has been linked to a variety of poor health outcomes. Much of this research has focused on total time spent sedentary, rather than on whether total sedentary time consists of long, uninterrupted stretches or shorter intervals. 

“There has been good evidence showing that being sedentary is harmful to health in a lot of ways, but it has been less studied in cancer,” Dr. Frederick Ho, a senior lecturer of public health at the University of Glasgow and lead author of the new work, told Technology Networks. 

Using data from over 91,000 UK Biobank participants with valid activity monitor data, Ho and his team aimed to determine whether more time spent sedentary was associated with increased cancer risk. 

They also examined whether long, uninterrupted periods of sedentary behavior affected cancer risk differently from shorter, interrupted sedentary periods. 

“To our knowledge, there haven’t been studies that looked at how sedentary time was accumulated,” Ho noted. 

Prolonged sedentary behavior is defined as lasting over 30 minutes, with minimal physical activity (less than 10%) in this time.  

“For example, if you work in front of a computer for an hour, during which you only left for a 30-second walk to get water, it is classified as prolonged sedentary behavior,” said Ho. 

Interrupted sedentary behavior is described as lasting less than 30 minutes, or if it lasts longer, is broken up with sufficient physical activity.

Different behaviors, different cancer outcomes 

Sedentary behavior was analyzed based on accelerometer data. Over 103,000 participants in the UK Biobank had device-recorded activity data, but 11,776 were excluded from the analysis for having a history of cancer at baseline, or for insufficient wearing time. 

The participants had worn the accelerometers for seven days, and the follow-up lasted approximately 12 years. While accelerometer data offer a more robust measure of physical activity than questionnaire-based assessments, the devices only captured behavior over a short period, which may not reflect habitual activity. The authors also noted that UK Biobank participants exhibit a known health-volunteer bias, meaning they are more likely to have higher activity levels than the general population, which may affect the generalizability of the study results. 

The researchers analyzed overall cancer mortality and incidence of overall, obesity-related, type 2 diabetes-related, and site-specific cancers in these participants. Multivariable models were used to adjust for potential confounders, including age, sex, ethnicity, deprivation, education, smoking status, and dietary factors. 

Participants who spent the most total time sedentary had a higher likelihood of cancer mortality, as well as overall, obesity-related, and type 2 diabetes-related cancer incidence. 

However, only prolonged sedentary behavior was associated with cancer risk and mortality. 

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“The data showed that it’s likely that prolonged sedentary behavior is more harmful in cancer incidence and mortality,” said Ho. “Of all the cancer types, we found the associations to be strongest in leukemia and oral cancer.” 

Each additional hour per day spent in prolonged sedentary behavior was associated with a 10% higher risk of cancer death. Prolonged sedentary behavior was also associated with a 12% increase in cancer incidence. 

Interrupted sedentary behavior showed the opposite effect—each additional hour per day was associated with a 19% lower risk of cancer mortality. 

Although the study doesn’t show that sedentary behavior causes poorer cancer outcomes, Ho noted that prolonged sedentary behavior affects biological pathways that may influence cancer risk. 

“Two plausible mechanisms are through the metabolic and inflammatory pathways,” he said. “Sedentary behavior displaces physical activity, which then reduces metabolic responses.” 

“Being sedentary is also associated with endothelial dysfunction and low-grade inflammation independent of physical activity,” he continued. 

Replacing sedentary behaviors with physical activity may lower cancer risk 

The researchers also investigated whether replacing prolonged sedentary behavior altered cancer risk. When just five minutes of prolonged sedentary behavior per day was replaced with vigorous physical activity, the authors observed a 22% lower risk of cancer mortality. Replacing one hour of prolonged sedentary behavior with light physical activity was associated with a 12% lower risk of cancer death. 

“We found that replacing sedentary behavior with physical activity was generally associated with lower cancer risk and mortality,” said Ho. “Generally, the higher the intensity of the physical activity, the lower the risk is.” 

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“However, it should also be noted that light-intensity physical activities, e.g., slower walks or household chores, are also likely to be beneficial, but we would likely need to do more of those to achieve an observable difference,” he noted. 

The findings of this study could inform future interventions to reduce cancer risk. Given the high prevalence of sedentary behavior, interventions that even modestly contribute to cancer prevention could have important implications for public health. 

“One important but less looked at intervention is light physical activity. These are relatively easy, accessible to most people, and could have a noticeable impact when done consistently,” said Ho. “It’d be very interesting to examine an intervention developed around light physical activity.” 

Reference: Zhou Z, Trost SG, Ryde GC, et al. Accelerometry-measured prolonged and interrupted sedentary behavior and cancer incidence and mortality: A cohort study of 91,292 UK Biobank participants. PLOS Med. 2026. doi: 10.1371/journal.pmed.1004767

About the interviewee: 

Dr. Frederick Ho is a senior lecturer in public health at the School of Health and Wellbeing, University of Glasgow, and a chartered statistician with the Royal Statistical Society. He currently serves as the deputy head of public health and leads the epidemiology specialism for the Master of Public Health program at the University. 

Ho holds a BSc in statistics from the Chinese University of Hong Kong, a PhD in epidemiology from the University of Hong Kong, and a PGCAP from the University of Glasgow. He has extensive experience working with complex big data, including Scottish and English primary care, hospital, and mortality records, national health surveys, and large-scale research cohorts, such as the UK Biobank and ALSPAC. 

His research focuses on uncovering the neglected complexity in applied epidemiology, particularly regarding nonlinearity, underlying mechanisms, and differential effects, in the context of early-life experiences, lifestyle factors, and cardiometabolic health.