Nearly 22 minutes of lost life for every hour of TV watched -- that's the measurement being quoted from a widely-reported Australian study of TV. Based on 11,000 adults, the study estimates that Australian males, averaging two hours of TV watching a day, will see their lifespan decrease by 1.8 years, and Australian females by 1.5 years.
So, is watching "Glee," "Law and Order" and "Monday Night Football" slowly killing you?
Not quite. Correlation is not causality.
It's not just politicians who adore one-sentence answers to highly complex questions. My national media experience includes one highly-attractive host who quickly laid down the interview rules: "Remember, keep it fluffy -- one sentence answers, no science." On another national TV channel, asked how both short and long sleep "caused" higher death rates, I tried to explain that people who sleep abnormally are often sick. My analogy was if 85 percent of Americans die in bed, that does not mean that beds kill people.
The Australian researchers are well aware of such confusion. In their abstract, they include the confidence interval for their data -- the standard statistically acceptable 95 percent range of possible answers. This assumes you accept the author's modeling of the numbers, and that the data follow normal (Gaussian) distributions -- two big assumptions. Even with those assumptions, the confidence interval of decreased lifespan varied between 8.4 days and 3.7 years for males, while the CI for females was a shorter span of 6.8 days and 3.1 years. This is rather similar to other studies performed in the U.S. at the Harvard School of Public Health, showing a 13 percent decrease in lifespan for each two hours per day spent watching TV. As the authors say, "This study is limited by the low precision with which the relationship between TV viewing time and mortality is currently known."
Folks, there's a big difference between 8.4 days and 1.8 years of "lost life." Nevertheless, different media outlets were able to state that one hour of TV watching was equivalent to two cigarettes .
But that's not correct, either.
TV or Not TV -- Is That the Question?
Not really. What matters is what TV watching represents -- primarily less physical activity. Watching TV -- especially for many hours -- really cuts down on physical activity. People who are watching TV are generally not moving then or other times -- either walking or other exercise.
So who does watch a lot of TV? Surprisingly, use of many Internet devices is not cutting TV time among teenagers and 20-somethings, who watch TV more than they use the Internet (though they often do both).
There are surprisingly few long-term studies of how physical and mental illness affect TV watching. However, it's no surprise that my and other clinicians' experience is that sick people watch a lot television. Depressed people watch scads of TV. And those mentally exhausted "relax" with TV -- particularly people who are feeling overworked and unable to pay the bills.
However, it's not just lack of exercise that correlates with TV watching. There is now data that people who sit a lot also have higher rates of death, even when they are exercising a lot. Sitting could be hazardous to your health.
Is it possible to watch TV without guilt? Even if you only watch science documentaries and the Royal Shakespeare Company, you may experience remorse at lost opportunities to prevent global famine, re-engineer the warming planet or visit your ailing great aunt.
But it is possible to make TV watching an active process which can help regenerate your body. Here are some suggestions:
1.Stand. There is no law that TV must be watched from a chair. You can stand, which depending on weight or gender, takes a quarter to 50% more calories than sitting; you can also pace if you like, which people commonly do with sports programs.
2.Watch socially. Social support is a very large factor in overall survival. If you can watch with family and friends, you'll be able to joke, cajole, discuss, and move around more easily -- as one writer describes her family very actively watching a Dallas Cowboys game.
3.Use an exercise device. It can be a simple stepper or something more elaborate like an elliptical or exercycle, but you can readily move watching TV -- and still stay in place.
4.Talk and walk. After the program is over, go and stroll with the people with whom you watched, discussing what you saw.
5.Don't eat while watching. Drink water or non-caffeinated drinks. People tend to not notice what they nosh while watching television, making it a further component of our obesity epidemic.
Bottom line: I believe that television probably won't kill you. Sitting can. Don't worry about "Glee" shortening your lifespan, if you sing and dance along.
Follow Matthew Edlund, M.D. on Twitter: www.twitter.com/therestdoctor