Is Sitting 'the New Smoking'? Absolutely Not

Kristin Jenkins

November 12, 2018

The health risks associated with long stretches of sitting are nowhere near comparable to those linked to smoking, according to epidemiologists and population health experts from Canada, Australia, and the United States.

What's more, almost 10 years of media reports claiming that "sitting is the new smoking" may have drawn attention away from the very real hazards of smoking, say Jeff K. Vallance, PhD, of the Faculty of Health Disciplines at Athabasca University, Alberta, Canada, and colleagues.

A review and analysis of the relatively small body of literature on sedentary behavior compared with extensive studies on smoking shows the risk estimates and absolute risk differences for smoking are almost 10 times worse than those for sitting, they note.

The lone exception is the risk for type 2 diabetes, which is almost doubled in people sitting for more than 8 hours a day, the authors say in their online perspective published November 1 in the American Journal of Public Health.

Media Reports on Risk of Sitting Far Outpace Scientific Evidence

"Any level of smoking increases risk of dying from any cause by approximately 180% versus a 25% risk increase for sitting," they write. "Promulgating direct comparisons of the health consequences of sitting and smoking is not recommended."

For instance, one of the most recent meta-analyses reported a hazard ratio (HR) of 1.22 for all-cause mortality associated with sitting and health outcomes.

By comparison, the relative risk (RR) of death from all causes for current smokers compared with never smokers was 2.80 for men and 2.76 for women. In heavy smokers who smoked 40 cigarettes a day or more, the RR was 4.08 for men and 4.41 for women.

These estimates correspond to absolute risk differences of more than 2000 excess deaths from any cause per 100,000 persons/year among the heaviest smokers compared with never smokers, Vallance and colleagues explain. In sharp contrast, comparison of people with the lowest and highest sit times revealed that the number of excess deaths per 100,000 persons was 190.

The authors point out that since 2010 media reports have suggested that too much sitting can be just as bad, or even worse, for health than smoking. One recent analysis found 300 news stories declaring that "sitting is the new smoking."

Claims such as this have "far outpaced the available scientific evidence," Vallance and colleagues say.

"It is obvious from examination of smoking research that sitting and smoking are distinct behaviors with different levels of associated risk."

Still, news coverage on the perils of sitting increased 12-fold from 2012 to 2016, their article shows. Stories appeared across the full range of media outlets, including top-tier publications such as Time magazine and those affiliated with respected clinical institutions, such as the Mayo Clinic Health Letter.

"Given the current state of the evidence, equating sitting with smoking is unwarranted, misleading for the public, and may serve to distort and trivialize the ongoing and serious risks of smoking," Vallance and colleagues warn.

They add that "Betteridge's Law of Headlines states that any headline that ends in a question mark can be answered by the word no. Is sitting the new smoking? No."

Smoking accounts for 21% of all deaths among men and 17% among women, the authors note. In 2012, the annual global cost of smoking-attributable disease was estimated at $467 billion, and it is anticipated that smoking will be responsible for one billion deaths in the 21st century.

In the US alone, an estimated $8.7 billion was spent by tobacco companies marketing cigarettes to Americans. "The economic burden of sitting is unknown and the relevant interest groups and amount of money spent are not comparable," the investigators say.

But Too Much Sitting Is Not Without Risks

Still, they add, too much sitting is not without its risks.

A study of 1.2 million people from 54 countries showed that the sitting-related all-cause mortality rate was 3.8%. One meta-analysis showed that the risk of type 2 diabetes was almost twice as high in people sitting for more than 8 hours each day compared with those sitting for less than 4 hours (HR, 1.9).

And for other common chronic diseases such as cardiovascular disease and all types of cancer, extended periods of sitting were also associated with increases in the risk of incidence and mortality, although they were much smaller at 10% to 20% (HR, 1.24 and 1.15, respectively).

The authors point out that these RR estimates correspond to an excess of about 33 cardiovascular disease-related deaths, 27 cancer-related deaths, and 610 incident cases of diabetes per 100,000 persons/year in people with the highest volumes of sitting compared with those with the lowest volumes of sitting.

Their analysis also showed that sitting is linked to an increased risk of depression (RR, 1.14).

In addition, a harmonized pooled analysis of more than one million people found significant associations between extended daily sit times, including television viewing time, and all-cause mortality in people with low levels of physical activity. Although the risks of longer sit times could be offset by 60 to 75 minutes of moderate to vigorous exercise each day, the exercise did not attenuate television viewing.

Either way, an hour or more of aerobic exercise each day is "probably unattainable for most," the authors point out.

"Researchers must work closely with their affiliated institutions to communicate their findings in the most responsible fashion," Vallance and colleagues suggest.

"The scientific community should also take efforts to transmit clear and accurate messages to the public and avoid sensationalized headlines that favor their positions or findings."

Vallance and study co-authors have reported no relevant financial relationships.

Am J Public Health. 2018;108:1478-1482. Full text

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