Saturday, 20 August 2011

This Hour costs 22 minutes

Another result I don't believe:
The amount of TV viewed in Australia in 2008 reduced life expectancy at birth by 1.8 years (95% uncertainty interval (UI): 8.4 days to 3.7 years) for men and 1.5 years (95% UI: 6.8 days to 3.1 years) for women. Compared with persons who watch no TV, those who spend a lifetime average of 6 h/day watching TV can expect to live 4.8 years (95% UI: 11 days to 10.4 years) less. On average, every single hour of TV viewed after the age of 25 reduces the viewer's life expectancy by 21.8 (95% UI: 0.3–44.7) min. This study is limited by the low precision with which the relationship between TV viewing time and mortality is currently known.
If people who watch six hours of daily television differ from other folks on margins other than TV-viewing, results here just might be overstated.

The paper just extrapolates to some actuarial tables the results of a prior article in Circulation. A couple things there to note:

  • There are no significant reported effects, after correcting for some health-related behaviours, for those watching less than four hours of television per day. And, saying that an hour costs 22 minutes is a bit nuts when the reference category is folks watching 2 hours of TV per day or less. Maybe there are effects for the "more than 6 hours per day" group. But that's hardly the same as saying that an hour of TV costs the moderate viewer 22 minutes.
  • The all-cause mortality relative risk even for folks in the >4 hour per day group has a confidence interval running from 1.04-2.05 after adjusting for those health behaviours that could be observed. That's almost touching the 1.0 mark; when the CI spans 1.0, results are insignificant. I wonder what would happen to those CIs on adjusting for more health behaviours.

HT: Alex Robson, who points to this journalistic account...

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