There are many people who spend a large part of their day glued to a chair, in many cases because they are working, traveling by car or resting on the couch, with a sedentary lifestyle being a true routine in the lives of many people. Until now we knew that it was harmful, but now science has put exact numbers on how an uninterrupted sedentary lifestyle influences our health, and the most important thing is that it has been seen that it does not help to compensate for it.
With a watch. A new study published in PLOS analyzed data from 91,292 people at UK Bank, and unlike other epidemiological studies that rely on questionnaires filled out by the participants themselves, here they used accelerometry. That is, for years they have monitored the physical movement of all these people thanks to activity sensors on the wrist.
After an average follow-up of 12.38 years, the researchers not only measured total inactivity time, but how it was distributed throughout the day. And that’s where the real enemy to our health comes in, which are blocks of uninterrupted time.
You have to get up. The central finding of the study does not penalize the simple act of sitting so much, but rather doing it continuously. The researchers concluded that each additional hour of prolonged sedentary behavior, understood as periods of 30 minutes or more without getting up at any time, is associated with a 10% increase in the risk of cancer mortality.
That is to say, spending long work days without moving at all is not free in the long term.
The solution. Fortunately, the results also show that the human body is incredibly grateful when we break that stasis. Using statistical time substitution models, the study calculated what happens when we swap prolonged periods in the chair for different “doses” of daily physical activity.
To give an example, replacing one hour a day of prolonged sedentary lifestyle with low-intensity activities such as walking at a normal pace or doing housework reduces the risk by 12%. But if we go further, changing just 30 minutes of uninterrupted sedentary lifestyle for moderate physical activity reduces the risk by 8%.
The most important thing. The most efficient substitution has been found to require very little time, as swapping sedentary time for just five minutes a day of vigorous physical activity reduces the risk of cancer mortality by a staggering 22%.
The golden rule. As is usual when analyzing medical literature, and as the authors and independent experts themselves emphasize, we must read the fine print. As it is an observational study, the data show a strong statistical association, but the design itself cannot demonstrate strict and absolute causality, leaving it exposed to certain biases, such as the UK Biobank volunteers usually having a healthier baseline profile than the population average.
However, this research does not arrive in a vacuum since it is tremendously consistent with previous scientific evidence and gives robustness to what we already suspected. In 2022, a meta-analysis and umbrella review already warned about the strength of the relationship between a sedentary lifestyle and oncological risk. And at a closer level, a study by the Carlos III Health Institute in 2024 confirmed in the Spanish population that replacing just one hour a week of sitting time with physical activity managed to reduce general mortality.
The experts. Nabil Djouder, head of the Growth Factors, Nutrients and Cancer Group at the National Cancer Research Center (CNIO), in a statement to SMC, pointed out that this study “reinforces the idea that sedentary behavior is an independent risk factor and that it is not enough to ‘compensate’ for it with occasional exercise.”
Images | Vitaly Gariev
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