It’s clear by now that sedentary behavior isn’t the healthiest thing in the world. Research out today, however, points to the added harms that can come from staying glued to a chair or the couch for long stretches of time.
Scientists at the University of Glasgow in Scotland and others examined wearable data from residents in the UK. People who spent prolonged periods being sedentary were more likely to later develop and die from cancer than people who interrupted their sedentary behaviors with bouts of physical activity, they found. The researchers argue that regularly breaking up your couch time, even with light movement, can meaningfully improve your health.
“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,” they wrote in their paper, published Thursday in PLOS Medicine.
The couch potato effect
Studies have consistently shown that the more time we spend being sedentary, the greater our risk of various health issues, including obesity, cardiovascular disease, and cancer. And health-related guidelines often emphasize cutting down on our total hours being sedentary.
Some research has suggested that replacing periods of sedentary behavior with physical activity can lower the risk of dying from cancer, but according to the authors, there’s been less focus on whether cancer risk is specifically affected by different patterns of being sedentary. In other words, does it matter, health-wise, if we’re spent the same amount of time constantly off our feet as compared to sometimes getting up?
To help find out, the researchers dug into data from the UK Biobank, a long-running project tracking the health of middle-aged residents in the UK. As part of the study, some volunteers wore activity trackers for a week, helping establish an objective baseline of their physical activity. All told, the researchers studied the outcomes of some 90,000 volunteers, who were followed for a median length of roughly 12 years. Prolonged sedentary behavior was defined as periods of at least 30 minutes where people barely moved for at least 90% of the time.
As expected, total sedentary time was associated with a higher relative risk of cancer incidence and mortality. But people who spent more time being sedentary for long periods appeared to be even worse off. Overall, prolonged sedentary behavior was associated with a higher risk of developing any cancer (including obesity- and type 2 diabetes-related cancers) and a higher risk of dying from cancer. And after adjusting for lifestyle and sociodemographic factors, each extra hour of prolonged sedentary behavior was associated with a roughly 10% higher risk of cancer death.
What to do
Of course, these findings can only show a correlation between prolonged sedentary behavior and cancer risk, not prove a cause-and-effect link. And the researchers note that volunteers in the UK Biobank tend to be healthier than the general public, which can possibly skew the interpretations scientists can make from studying them.
At the same time, other research has similarly suggested that prolonged sedentary behavior is especially bad for our health, including research conducted in the lab. “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,” the researchers wrote.
On the positive side, simply taking breaks in your couch-surfing does seem to help. The researchers calculated that replacing an hour of prolonged sedentary behavior with even light physical activity, for instance, was associated with a 12% lower risk of cancer death, while replacing just five minutes a day with vigorous exercise was associated with a 22% lower risk.
“Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement shouldn’t be ignored,” the researchers wrote. “Moving forward, clinical trials will help us move beyond blanket advice and develop personalized strategies for breaking up sitting time.”
So yes, you should try to be less sedentary in general. But if you’re a sucker for long binge watching or gaming sessions, as I certainly am, then the very least you can do is regularly take breaks in between.
