Watching TV Could Shorten Your Life

Daily TV viewing is statistically associated with an increase in the risk of death from cardiovascular disease and other medical causes, according to a new study in Circulation. Study author David Dunstan explains the findings.

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IRA FLATOW, host:

The old adage, don't sit too close to the TV, might also need a revision - try don't sit in front of the TV at all. A new study links time in front of the tube with increased risk of death, and we're not talking about, you know, radiation that might be coming out of the front of your TV like in the old days.

The study published in the American Heart Association journal Circulation -listen to this: It found that for every hour of daily TV time, that correlated with an 18 percent increased risk of death from cardiovascular disease. But it isn't just heart disease. Each hour of couch potato-ing was linked with an 11 percent risk from death from all causes.

Here to tell us what makes TV time bad for your health is the study author, David Dunstan; he is the head of physical activity at the Baker IDI Heart and Diabetes Institute in Melbourne, Australia. Welcome to SCIENCE FRIDAY.

Dr. DAVID DUNSTAN (Baker IDI Heart and Diabetes Institute): Oh, good afternoon.

FLATOW: Good day. Good afternoon. Good evening.

Dr. DUNSTAN: Good day.

FLATOW: Good day. Day good day to you. Is that true, it doesn't matter - is it just sitting down and not doing something that the problem is here?

Dr. DUNSTAN: Well, I guess that's a very important point, that it's not television itself per se that is the problem. What we believe is that it's what people do whilst they're watching television, because we know that the default position for many of us when we're watching television is sitting. And this new evidence adds to the evidence that too much sitting is potentially bad for our health.

FLATOW: And how much sitting do you have to do to start noticing there's a problem?

Dr. DUNSTAN: Well, I guess, within this study, you've already mentioned some of the findings, but another key finding was that when we compared people who watch less than two hours of television per day, people who watch more than four hours a day had a 46 percent higher risk of death from all causes and an 80 percent increased risk of death from cardiovascular disease. So it appears that the higher amounts of TV significantly increase the risk.

FLATOW: Forty-six percent, four hours a day. That - you know, the statistics in the United States are showing that the average person watches about five hours of TV a day here.

Dr. DUNSTAN: Yeah. And within Australia, our average is around about the three hours per day. So it does have serious implications, particularly for the U.S., for the population where, you know, TV viewing is substantially higher than what exists here in Australia.

FLATOW: So if you're not sitting on the couch, if you just stand up and walk around or - that would be okay while you're watching television.

Dr. DUNSTAN: Well, I guess the key point here is that what I'm providing evidence about is that too much sitting is bad for health and, you know, we simply, from our lifestyle changes that have been induced by our modern society, many of us simply move from chair to chair throughout the day, from the seat in the car to the chair in the office to the couch at home.

So what we've tended to underestimate is the true benefit that can be derived from this incidental or this non-sweaty type movement, because what we've seen is that the more you move, the greater the likely benefits for your health.

FLATOW: What goes on in your body to make just these simple movements? You don't have to be aerobic, as you're saying, you just have to move around a bit. What's going on in your body to help you?

Dr. DUNSTAN: Well, the possible explanation for this really comes down to the muscles moving. And when we're sitting for prolonged periods, we're not burning up much energy. And it appears that television contributes to an overall reduction in the amount of calories that we burn throughout the day. In fact, there are studies that have actually shown that when we're sitting watching television, we burn as much energy as what we do when we're sleeping or at rest. So it's very low energy expenditure, and over a period of, you know, four or five hours, that's quite low energy expenditure.

The other consequence that we're starting to understand now is that when we're sitting for prolonged times such as, you know, in front of the television or long hours in front of the computer screen at a desk, there's an absence of muscle contractions. And there's extensive evidence that indicates that muscle contractions are so essential for many of the body's regulatory processes - for example, the breaking down and using of glucose. So when we're remaining idle for prolonged periods, we're disrupting those body's typical regulatory processes.

FLATOW: So get off your chair and get up and move is what you're saying. Get out of the car, take a walk. Just something - a little bit, doesn't - you don't have to, you know, do a lot of sweaty exercise is what you're saying.

Dr. DUNSTAN: Well, I think the important point here that this does not negate the important benefits of undertaking regular exercise. There's substantial evidence that exercise is important.

But what we now have to take stock at is looking at - what are we doing when we're not exercising or we're not sleeping, which for many of us, even if we exercise for 30 minutes to 60 minutes of the day, that still leaves 15 hours of the day - if we sleep eight hours, that is - for this non-exercise time, non-sleeping time. So what we're trying to encourage people is to think about avoiding prolonged periods of sitting, move more, more often.

FLATOW: So you're saying that even people who you studied who are really good exercisers, who are very active and they exercised, you know, like we see most people telling us that we should be doing, and they're on the treadmill or whatever, even those people, when they sat down for awhile, they fell right into that category.

Dr. DUNSTAN: And this is a really interesting finding, and that is the case. And what we did, we factored in people's exercise levels into our analyses. And even when we factored that in, the relationship between TV remained robust. That is, it persisted even when we account for people's exercise levels, which I think this indicates that you can still exercise, but spend higher amounts of the remainder of the day sedentary, or you can still watch significantly high amounts of television, with more - the higher amounts of television led to the increased risk.

FLATOW: This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow, talking with David Dunstan. Let's go to the phones to Brandon in Bellingham, Washington. Hi, Brandon. Brandon, are you there? Hello, Brandon - no. Three, two, one - strike three.

Yeah, he wanted to ask a question. I think you might have answered it already -does it make a difference if you're just sitting and reading a book? You know, television was used as the model in the study, but I guess just sitting and reading a book would have the same effect.

Dr. DUNSTAN: No, that's a good point. And as you indicated, within the study we specifically focused on television because we had previously seen that to be a good indicator of a person's overall sedentary behavior pattern. I guess the message that I come back to again here...

FLATOW: Right.

Dr. DUNSTAN: ...is that it's the sitting time that appears to be detrimental to health, and of course prolonged sitting while I'm reading, great for the mind...

FLATOW: Right.

Dr. DUNSTAN: ...but I think the important point here - don't stop your reading, get up and move frequently throughout the movie - through the reading, is probably the important message.

FLATOW: Well, this is great for people who are throwing Super Bowl parties, you know, because instead of just sitting on the couch, they're up yelling, screaming, going around and, you know, carrying on.

Dr. DUNSTAN: Yeah. We often get asked, so what can we do if we want to watch our favorite TV show? Well, one strategy would be to utilize the commercial breaks or the breaks in the TV show to get up and move about and get those muscles moving. Again, move more, more often. If you're standing up and moving about, you're not sedentary.

FLATOW: Mm-hmm. And did you look at diet at all? Did that make any difference?

Dr. DUNSTAN: Yeah, that's a very good point. And we did account the people's diet overall in terms of their diet quality. And even when we accounted for that, the relationship still persisted. But what there has been evidence earlier, from other studies, is that increased poor snacking may take place with television viewing due to the, you know, the cues that people have through commercial breaks and television shows. But we didn't address that, or we haven't addressed that just yet. We are now moving towards starting to understand that a little bit more.

FLATOW: Is there any minimum? Were you able to find out what minimum amount of movement we would need to offset that clock that's ticking?

Dr. DUNSTAN: That is the question that we need to explore further within our research. And we're actually moving a little bit more towards looking at this in an experimental level by having people come in to our laboratory. And we asked them to sit for the seven hours. But on another day we asked them to sit but we get them up every 20 minutes for two minutes, to see whether that interruption can lead to more favorable blood glucose levels, blood fat levels. So I think it's stay tuned for that one, because that's where we're currently working on.

FLATOW: So you did bring people and have them get up every 20 minutes, and you're still working on that data is what you're saying.

Dr. DUNSTAN: Yeah. We're still working on that data. We've - we're halfway through the collection of that data. But that will give us some, you know, important insights to the question that you just asked there in terms of how often should we get people up and how long for.

FLATOW: So if you're going to be watching TV, walk around a bit, you know, or get on the treadmill when you're watching, even if you're just walking slowly on it, just to do some sort of movement.

Dr. DUNSTAN: Also complete some of our household chores if that's feasible, you know, the folding of the washing or the washing of the dishes while we're watching our favorite TV show. The important point here is not to, you know, miss your favorite TV show, but keep moving while you're watching that favorite TV show.

FLATOW: Back to "Ozzie and Harriet," which was a big show in the old days. But I don't think she ever folded anything.

(Soundbite of laughter)

FLATOW: All right, thank you very much for taking time to be with us today.

Dr. DUNSTAN: Well, thank you very much for the opportunity.

FLATOW: And thanks for staying out late for us. David Dunstan is head of physical activity at the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, which is probably about 17 hours ahead.

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