Modern work, various forms of transit, and entertainment technology have made humans more sedentary than ever before. Since this lifestyle shift has only been established in the last few hundred years, our bodies may struggle to exist in a mostly sitting or lying position.
Many studies have already shown potential harmful effects prolonged sitting can have on our health, like raising the risk of heart disease and cancer, but most research has only looked at correlations between total time spent sedentary in a day without accounting for length of intervals. Researchers from the University of Glasgow wondered: Does it make a difference in health outcomes if people break up their sitting sessions?
As described in their recent paper published in PLOS Medicine, the researchers did see a distinction. A large health record database showed that uninterrupted sedentary behavior was linked to a 9 percent higher risk of cancer death, while substituting one hour of sedentary behavior with light physical activity lowered the risk.
“Our findings suggest that the health effects of sedentary behavior may depend not only on total sedentary time,” summarized the researchers in the study, “but also on whether that time is accumulated in prolonged bouts or interrupted by activity.”
Explore All OptionsSitting and Negative Health Outcomes
Sedentary behavior generally refers to waking activities that use very little energy, such as sitting, reclining or lying down, and can account for roughly 55 percent of waking hours in both children and adults.
Previous research has associated spending more time sedentary with a range of health problems, including cardiovascular disease, type 2 diabetes, obesity, certain cancers and premature death from any cause. There is also evidence that swapping some sedentary time for physical activity may reduce the risk of dying from cancer.
But simply counting up the hours spent sitting may miss a small but important nuance: how those hours are accumulated.
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Prolonged Versus Interrupted Sedentary Behavior
To investigate, the research team used data from 91,292 UK Biobank participants who had recorded their activity while wearing accelerometers for seven days. The participants were then followed for an average of 12.38 years.
The researchers separated sedentary behavior into different patterns. Prolonged sedentary behavior meant spending at least 30 minutes in a bout that was at least 90 percent sedentary. Interrupted sedentary behavior included shorter periods or sessions broken up by more than 10 percent non-sedentary activity.
The results showed that people who spent more time in prolonged sedentary bouts had a 9 percent higher risk of dying from cancer. This pattern was also associated with a higher risk of developing cancer overall, as well as obesity- and type 2 diabetes-related cancers.
Interrupted sedentary behavior, meanwhile, was associated with lower risks across the outcomes studied. Replacing just one hour of prolonged sedentary time each day with light physical activity was associated with a 12 percent lower risk of cancer mortality.
“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,” wrote the researchers in their study.
Updating Current Health Guidelines
Still, the findings come with some limitations. This was a single-cohort study based on UK Biobank volunteers, who tend to be more physically active and healthier than the general UK population. The results therefore may not apply to everyone, and the study cannot prove that prolonged sitting directly causes cancer deaths.
The researchers also didn't have information about what participants were doing while sedentary. Sitting at a desk, driving a car, and watching television, for example, may have different effects.
“Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement shouldn't be ignored,” added the authors in a press statement. “Moving forward, clinical trials will help us move beyond blanket advice and develop [personalized] strategies for breaking up sitting time.”
For now, the message isn't necessarily to panic every time you sit down. Instead, it may be another reason to look for small opportunities to move throughout the day.
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in PLOS Medicine: Accelerometry-measured prolonged and interrupted sedentary behavior and cancer incidence and mortality: A cohort study of 91,292 UK Biobank participants
