When Flashy Headlines Inflate Science

There’s been some buzz in the media recently surrounding a new study about sitting and life expectancy. This is how two media outlets headlined their reports on the research:

Limit TV watching to 2 hours to live longer, say scientistsThe Telegraph, July 10, 2012
Study: Excessive sitting cuts life expectancy by two yearsUS News, July 9, 2012

I wouldn’t be surprised if these stories got a lot of clicking and viewing attention. Chances are readers were sitting down when they came across these and were eager to learn more about this apparently deadly habit they were engaging in.

So what inspired these headlines? Researchers from the Pennington Biomedical Research Center and Harvard Medical School looked at five recent studies linking sitting time and television viewing to life expectancy. They compared the results of the studies to the prevalence of these behaviors in the United States based on the National Health and Nutrition Examination Survey and found that reducing sitting time to less than 3 hours a day could potentially increase American life expectancy by 2 years. Reducing TV time to less than 2 hours a day could add over a year. Their results were published in the journal BMJ Open earlier this month.

But – and this is a big but – their study comes with some caveats:

1. This study relied on self-reported engagement in sedentary behaviours, which introduces the possibility for error and recall bias.
2. The results of several recent studies have suggested that the effects of sedentary behaviour on health may be independent of the effects of physical activity per se
3. This should not be interpreted to mean that people who are more sedentary can expect to live 1.4 or 2.0 years less than someone who does not engage in these behaviours as much. Life expectancy is a population statistic and it does not apply to individuals.

These points are quoted directly from the article. The message here is that in this study, as in all scientific research, there is ample room for error. People are not so good at accurately reporting their behavior, which can skew prevalence rates. It may not be the actual sitting that’s bad for your health, but rather the lack of physical activity. And, most importantly, this study projects gains in life expectancy only if a large number of Americans reduced their daily sitting time – this could have an effect on the country’s average life expectancy, not that of an individual person.

The real takeaway from this research is that, assuming there is a relationship between sitting behavior and mortality, being sedentary can have health repercussions similar to those of smoking, which also accounts for about 2 years of life expectancy at birth.

This is a great case study of how science gets reported, or misreported, in the media. The Twitter age has rendered too many of us into mindless media consumers, simply taking in headlines and blurbs at face value without any real questioning of legitimacy. There certainly is a lot of good science and health reporting out there, but do yourself a favor: if a headline claims that scientists have discovered a human immortality supplement, read on before sending it out to your friends.

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