Risk: being physically inactive or sitting too long?


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Several media outlets have highlighted these concerns (here and here). Some organizations go so far as to compare sitting to smoking: one study even found 600 press articles between 2012 and 2016 making the comparison (“is sitting the new smoking?”).

Effects of sitting on health

Over the past decade, few studies have actually investigated this question. For example, in 2012, a British team analyzed 18 studies and concluded that “sedentary” behaviors are associated with an increased risk of type 2 diabetes, cardiovascular disease, and death from any cause.

Another 2015 study that looked specifically at TV viewing (an activity typically done while sitting) found that “longer” viewing (defined as an increase of 2 hours per day) over 14 years was associated with a higher rate. risk of death.

Finally, according to a Swedish occupational health study published in 2021, people who sit all the time at work say they feel less healthy and suffer more from neck and back pain.

Of course, the effect of sitting depends on the time spent there. Data suggest negative consequences of sitting for more than 7 hours a day, explained Canadian and Australian researchers in a 2018 review of the latest scientific literature.

What is a sedentary lifestyle?

However, as recently as 2006, an international team of researchers questioned the fact that different studies on sedentary lifestyles did not always use the same definitions to describe sitting, making interpretation of results difficult.

The problem begins with the definition of “sit”. The Canadian and Australian researchers quoted above note that sedentary behavior includes not only the sitting position, but also all awake behaviors characterized by “low energy consumption”. This applies, for example, to the stagnant state of what is offered at checkouts, as already noted in a 2006 study, which can lead to many additional problems.

Although the researchers included time spent in front of the TV in sitting hours, a 2006 paper argued that this could have skewed the results. This view is shared by Australian researchers who in 2016 tried to determine whether sitting a lot increased the risk of premature death. They point out that TV viewing is associated with several confounding and less healthy factors, such as snacking.

Danger: to sit or not to move?

These Australian researchers evaluated eight systematic reviews (i.e. eight summaries of studies) based on the Bradford Hill criteria (nine criteria widely used in epidemiology) to assess whether there was a causal relationship. Their conclusion is that there is indeed a “strong” relationship between sitting time and mortality, particularly because of the stability of this relationship over time. The authors note that this association was only seen in less active people, which brings us back to the notion of a “sedentary lifestyle.”

A 2006 paper also noted that the association between sitting time and mortality appears to depend on individuals’ physical activity levels. Similarly, two studies conducted in 2014 and 2015 found that the risks associated with sitting time were higher in people who were not physically active.

According to these researchers, we must therefore ask ourselves whether sitting actually has consequences independent of a general lack of physical activity. Australian researchers disagree: they note that it is possible to be very active in general by spending a lot of time sitting.

Replace idle time with active time?

Recently, a three-country study concluded that reducing sitting time may not be enough to improve the health of people who are completely sedentary. In other words, replacing sitting time with standing time will not be enough: it would be better to replace it with walking or more vigorous activity.

a published study Lancet In 2016, it concluded that 60 to 75 minutes of physical activity per day offsets the risk posed by sitting for 8 hours or more per day. In other words, according to the first author of the article, one hour of physical activity would compensate for 8 hours of inactivity.

A 2006 study already suggested this: rather than advising people to spend less time sitting, we should encourage them to move more, regardless of the intensity of the activity.

Judgment

Spending a lot of time sitting is actually associated with an increased risk of death. However, this association is likely due to the lack of physical activity rather than the task itself.

Photo: Marc Mueller/Pexels

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