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Sedentary time is unhealthful, even if you’re an exerciser

We know that physical activity is good for health.

But is the reverse also true: Is sitting — being sedentary — bad for health?

A study published last week in the online version of Circulation, the medical journal of the American Heart Association, suggests that it is. A team of Australian researchers reported that every hour a person spends watching TV each day is associated with an 18 percent increased risk of dying from cardiovascular disease and an 11 percent increased risk of dying prematurely from all diseases.

The more time spent glued to the TV, the greater the risk. Among the 8,800 adults who participated in the 6½-years-long study, those who watched the most TV — four or more hours a day — were 80 percent more likely to die of cardiovascular disease and 46 percent more likely to die of any cause than their peers who watched two hours or less.

But here’s the finding that should really get you up and out of your chair: The study discovered that the association between TV watching and death from cardiovascular disease was not only independent of such risk factors as smoking, blood pressure, cholesterol, weight and diet, but also of exercise.

In other words, being a couch potato may wipe out some or all of the benefits you get from your daily workout.

And Americans are notorious couch potatoes. One of the things that struck me while reading the Circulation study was how low the average household TV viewing time is in Australia: about three hours. Here in the States, the average household TV viewing time is about eight hours.

In fact, the only thing we Americans spend more time doing each day than watching TV is sleeping.

Of course, this study has its limitations. People who watch a lot of TV may be unhealthier to begin with, and although the Australian researchers took steps to eliminate such confounding factors, it’s possible that undiagnosed illnesses could have been responsible for some participants’ long hours in front of the TV. Furthermore, the participants self-reported how much time they spend watching TV. Such self-reports can be unreliable. (Who likes to admit, even to themselves, how much TV they watch?)

A new paradigm?
A lot more is known about the physiological reasons exercise helps people stay healthy than about why sedentary behavior might cause people’s health to deteriorate. Research suggests, however, that sitting for long periods of time may harm health by increasing blood glucose and cholesterol levels as well as body fat.

This study isn’t the first to show that being sedentary can be harmful to health regardless of physical activity. Recent studies from Canada and Japan have reported similar findings.

Given all this new data, it’s time we start thinking about sedentary behavior in a new way, argue three Swedish exercise specialists in an editorial published online Tuesday in the British Journal of Sports Medicine. [Note: The editorial does not appear to be available to general readers yet.]

Using the term sedentary behavior as a synonym for not exercising is misleading, they write. We should instead think of it as muscular inactivity.

In other words, when it comes to assessing our healthful behavior, we not only have to think about how much exercise we’re getting, but we also need to consider how much sitting around we’re doing.

“In the future,” the Swedish experts write, “the focus in clinical practice and guidelines should not only be to promote and prescribe exercise, but also to encourage people to maintain their intermittent levels of non-exercise daily activities. Climbing stairs rather than using elevators and escalators, 5 minutes of break during sedentary work, or walking to the store rather than taking the car will be as important as exercise.”

Excuse me. I’m going to get up from my desk now for a five-minute break. …

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Comments (4)

  1. Submitted by Ross Williams on 01/20/2010 - 01:53 pm.

    Is it TV itself, rather than the sedentary nature of the activity, that causes the problem either directly or indirectly. Or are computer users, readers, etc. also at risk?

  2. Submitted by Susan Perry on 01/20/2010 - 04:56 pm.

    It looks like it’s the sedentary activity. Not good news for a writer like me who exercises regularly, but sits in front of her computer all day.

  3. Submitted by Sheila Ehrich on 01/21/2010 - 12:58 pm.

    So to expand on Ross’s comment above. My job REQUIRES that I sit in front of a computer screen for a minimum of 8 hours a day (much like you Susan), so that already enormously increases my risks. And the fact that I spend another two to three hours a day comeing and going to work in a car also adds more risk.

    So even though I try to exercise at least 30 minutes a day (in winter – more in the summer) and one of my hobbies is gardening, if a partake of one of my other hobbies – reading – I’m really putting myself at risk? So do I quit my job? Quit reading? What is someone in my position supposed to do? It’s great to have all these studies that outline risks, but where are solutions to the problem.

    I know the Mayo clinic has people walking on treadmills while being on their computers. However, I can’t honestly see a company like ours going out and buying that many treadmills. And frankly, I’m not sure how well I would be able to do my job while walking on a treadmill all day.

    What are some realistic solutions?

  4. Submitted by Susan Perry on 01/21/2010 - 09:41 pm.

    Sheila:

    First of all, this research is showing a correlation, not a cause and effect. Other factors could be involved. Maybe, for example, people who watch TV make poorer food choices in terms of nutrition. Or something else might be going on. These studies can’t control for everything.

    What some of these researchers seem to be suggesting (and, at this point, they’re only making an educated guess) is that not moving for long stretches of time may have some kind of negative physiological effect separate from not exercising. So one practical suggestion would be to get up from your desk every hour or so and just move around a bit. Walk down the hallway, for example, or stretch at your desk–anything to move your muscles. That’s good advice even if this line of research eventually doesn’t pan out.

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