Correlation is not Causation

According to a somewhat dry AFP article (posted on a URL that will probably expire soon), “The researchers estimated that in 2008 Australian adults aged 25 and older spent 9.8 billion hours in front of the small screen, and that this time was associated with 286,000 years of life that ended prematurely. | Every single hour of TV watched after the age of 25 shortened the viewer’s life expectancy by just under 22 minutes, according to an extrapolation of these figures.”  That article is published under the headline says “Daily exercise ‘may prolong life'”

An MSNBC headline-writer sexed that detail up with a must-read headline that screams

Study: An hour of TV can shorten your life by 22 minutes

The space-filling article, credited to “ staff and news service reports,” does state

The problem is not actually TV itself but the lack of activity by the viewer for long periods, the researches [sic] said. Cardiovascular disease, diabetes, excess weight and other health problems are associated with a sedentary lifestyle.

But that sedate description, together with the half-hearted weasel word “can” in the headline, does little to excuse the exaggeration claim.

Of course, what this means is that, on average, people who watch a lot of TV tend to be less active. The researchers found a statistical correlation between amount of TV watched and lifespan, but someone who watches TV while on an exercise bike for 2 hours a day is likely to be in much better shape than someone who watches no TV but sits on the couch all day reading books.