A study found that each additional hour spent in prolonged, uninterrupted sedentary periods was linked to a 9% greater risk of dying from cancer.
The research was published in PLOS Medicine.
Previous research has connected sedentary behavior, including sitting, reclining, and lying awake, with worse health outcomes.
However, health recommendations have generally focused on the total amount of sedentary time.
This study suggests that how that time is spread out may also be important.
Several shorter periods of sitting may have different health associations than staying inactive for extended stretches.
Study Followed More than 91,000 People
Researchers analyzed data from 91,292 UK Biobank participants.
Everyone wore an activity monitor for seven days, and researchers followed them for a median of 12.38 years.
Prolonged sedentary behavior meant periods lasting at least 30 minutes in which at least 90% of the time was sedentary.
Interrupted sedentary periods were shorter or included more movement.
Longer Sitting Was Linked to Cancer Risk
People who spent more time in prolonged sedentary periods had higher risks of cancer death and overall cancer diagnoses.
The association also appeared with obesity-related cancers, including colorectal, breast, liver, kidney, pancreatic, ovarian, thyroid, and esophageal cancers.
Cancers connected with type 2 diabetes showed a similar association.
By contrast, interrupted sedentary behavior was linked with lower risks across the outcomes researchers examined.
The researchers also looked at replacing prolonged sitting with movement.
Replacing one hour of prolonged sedentary time each day with light physical activity was associated with a 12% lower risk of dying from cancer.
Study Has Several Limitations
The research involved only UK Biobank volunteers. That group tends to be healthier and more physically active than the broader UK population, so the findings may not apply to everyone.
Because this was an observational study, it doesn’t prove that prolonged sitting causes cancer or cancer deaths.
Researchers also lacked details about why participants were sitting, such as whether they were working or driving.
Still, the findings suggest that breaking up long periods of inactivity could have health benefits.
The researchers say future clinical trials could help determine whether regularly interrupting sitting lowers health risks and could lead to more personalized recommendations for reducing prolonged sedentary time.
