Watch TV and die
A paper in the journal Circulation last month prompted lots of excitement in the media. Small wonder: it said that watching TV increases your chances of dying. The more you watched, the worse for you.
Or at least that’s how it was reported. The Times ran with: “Television watching can shorten life”, The Guardian with: “Watching television increases risk of death from heart disease”, while The Daily Telegraph said: “Every hour per day watching television "increases risk of heart disease death by a fifth”.
Did the study really say that? And if it did, how persuasive was the evidence?
The research was conducted in Australia by Professor David Dunstan of the Baker IDI Heart and Diabetes Institute in Melbourne and colleagues from Australian universities. A cohort of 8,800 people were asked a lot of questions about their diet, lifestyle, age, sex, and TV viewing habits. They were followed up for an average of 6.6 years, in which time 284 of them had died. The team found a weak but statistically significant correlation between the hours of television-viewing and the likelihood of dying due to all causes or cardiovascular diseases.
Compared with those who watched TV for less than two hours a day, those who watched for more than four hours a day had a 49 per cent greater chance of dying of all causes (risk ratio 1.49, 95 per cent CI 1.06-2.09) and a 85 per cent greater chance of dying from cardiovascular disease (risk ratio 1.85, CI 1.03-3.33). There were very few heart deaths – just 22 in the most TV-addicted group, and 87 in total
The conclusion? “Television viewing time was associated with increased risk of all-cause and CVD mortality.”
But only just. The authors stress repeatedly that the correlation is weak and of borderline significance in most cases, and further note:
(1) The study used TV viewing as a measure of sedentary behaviour. The authors claim that this is a good enough proxy for other sedentary behaviour patterns. But this obviously means that it isn't necessarily television-watching that can increase the risk of death. Hours spent watching TV while doing other activities – ironing, or cooking, for example – weren’t counted.. So, does sitting by the window and staring out of it for over four hours a day also increase the risk of death? If it does, then television is not the specific factor.
(2) The viewing times were self-reported, so respondent bias cannot be ruled out. And TV viewing and exercise were assessed only at the start of the study. This meant that any lifestyle changes in the following years haven't been accounted for.
(3) There is the possibility of confounding. The authors clearly state: “Although we adjusted for several potential confounding variables, it is possible that other unmeasured or unknown confounding factors may have accounted for the associations that we have reported.”
(4) The possibility of reverse-causality, that is, where undiagnosed or other conditions may have limited mobility and caused an increased television-viewing time, have not been ruled out.
(5) The authors acknowledge that those who spent more time watching television in general had worse health. Measures of BMI, waist circumference, blood pressure, total cholesterol, triglycerides and fasting glucose at the start of the study were all higher in those who watched the most hours of TV a week. These factors alone would have accounted for higher heart deaths, and although they were corrected for, it is open to argument whether that correction is adequate.
(6) Finally, they also showed that those with the longest hours in front of the box were less likely to have completed 12 years of education. Given the strong association between education level and disease, this may have biased the results despite tests that showed education levels did not significantly modify the associations between TV-watching and dying.
At best, this study shows that sedentary behaviour, of which hours of TV-watching is a proxy, is associated with modest elevations in death from heart disease and from all causes. There is nothing intrinsic in television that makes people more likely to die. And, given the limitations of the study,
television executives can breathe a sigh of relief.
To be fair, The Times, Guardian and Telegraph all quoted Professor Dunstan making these points, and can hardly be criticised for reporting the study as they did, given that Circulation had given it the title: Television Viewing Time and Mortality. Reporting in a newspaper a study that shows weak associations without leaving an exaggerated impression of the findings is extremely difficult.
Poorna Mazumdar (not verified) wrote,
Thu, 11/02/2010 - 12:50
They should've asked for a medical background as well, then, shouldn't they? If you're asking all kinds of questions. And anyway,did the question specifically ask whether they sat on a couch and watched tv? If it didn't lounge about but did it, as the author of the article states, while doing chores or at work, the behaviour pattern points to lack of other options for recreation rather than sedentary lifestyle. Unimaginative, maybe. Sedentary? Questionable.
Either way, well written article. Makes you wonder. About, amongst other things, how right Roald Dahl was in frowning at telly-watching for kids.
Achintya Rao (not verified) wrote,
Thu, 11/02/2010 - 12:58
Well, you can give the study a read for yourself and figure it out. They did consider medical backgrounds, and factored those in. Didn't affect the results by much, apparently.
You make a good point about whether the actually SAT down and watched TV, but I can't think of many who do so whilst on the treadmill. However, it's a decent proxy, I concede.
You should consider doing a study on how being unimaginative can increase the risk of death!
Charlotte King (not verified) wrote,
Fri, 12/02/2010 - 09:41
I like, a well-written article. But in my experience to some degree all studies are like this, scientists usually stress that these results 'could' mean something or 'might' allow the development of a cure and it is definitely hard to write an interesting story that people will read without stretching the truth a little
madison toner (not verified) wrote,
Fri, 09/04/2010 - 17:54
lol
Varsha (not verified) wrote,
Fri, 13/08/2010 - 06:56
Nicely written piece. It's a much-known fact that the media carries sensational reports even if the studies didn't imply anything quite as dramatic. All talk of statistical significance, correlation or confidence intervals is wasted on a lay reader. From a newspaper editor's point of view, a subject linking TV to death translates into more eyeballs whereas a mention of technical terms (even as a disclaimer) is counter-productive. So, as long as one takes these reports with a pinch of salt, it's fine. I'd rather have hyperbolic news articles than any more mention of Katie Price.
Anonymous (not verified) wrote,
Mon, 03/01/2011 - 23:43
I have been watching tv for about 3 hours straight and I kinda am now I'm trying to turn around and close my eyes on the commercials and I can't really breathe. Is that because of the tv or it's just me overexaggarating