Heart Risk Increased By Prolonged TV Viewing

Sitting for long periods of time has
been linked to increased risk of cardiovascular disease and early death, but a
new study suggests that not all types of sitting are equally unhealthy.

The study, led by researchers at
Columbia University Vagelos College of Physicians and Surgeons, found that
leisure-time sitting (while watching TV)–but not sitting at work–was
associated with a greater risk of heart disease and death among the study’s
more than 3,500 participants. The study also found that moderate-to-vigorous
exercise may reduce or eliminate the harmful effects of sedentary television
watching.

“Our findings show that how you
spend your time outside of work may matter more when it comes to heart health,”
study author Keith M. Diaz, PhD, assistant professor of behavioral medicine at
Columbia University Vagelos College of Physicians and Surgeons and a certified
exercise physiologist. “Even if you have a job that requires you to sit
for long periods of time, replacing the time you spend sitting at home with
strenuous exercise could reduce your risk of heart disease and death.”

The study was published online today
in the Journal of the American Heart Association.

Background

A growing body of research shows
that people who are sedentary–especially those who sit for long, uninterrupted
periods of time–have a higher risk of cardiovascular disease and death.

But most previous studies did not
follow people over time, making it difficult to draw conclusions about the
relationship between sedentary behavior and health risk. These studies have
included mainly people of European descent rather than African Americans, a
group that has a higher risk of heart disease compared with whites. Previous
studies also measured physical activity using an activity monitor, which is
unable to distinguish between different types of sedentary behavior.

What the Study Found

The new study followed 3,592 people,
all African Americans, living in Jackson, Miss., for almost 8.5 years. The
participants reported how much time they typically spent sitting while watching
TV and during work. They also reported how much time they spent exercising in
their down time.

The participants who had logged the
most TV-viewing hours (4 or more hours a day) had a 50% greater risk of
cardiovascular events and death compared to those who watched the least amount
of TV (less than 2 hours a day).

In contrast, those who sat the most
at work had the same health risks as those who sat the least.

Even for the most dedicated TV
watchers, moderate to vigorous physical activity–such as walking briskly or
doing aerobic exercise–reduced the risk of heart attacks, stroke, or death. No
increased risk of heart attack, stroke, or death was seen in people who watched
TV for 4 or more hours a day and engaged in 150 minutes or more of exercise a
week.

Why Does the Type of Sitting Matter?

In a previous study, Diaz found that
excessive sitting is linked to worse health outcomes, and even more so when
sitting occurs in lengthy, uninterrupted bouts.

“It may be that most people
tend to watch television for hours without moving, while most workers get up
from their desk frequently,” Diaz says. “The combination of eating a
large meal such as dinner and then sitting for hours could also be particularly
harmful.”

“More research is needed, but
it’s possible that just taking a short break from your TV time and going for a
walk may be enough to offset the harm of leisure-time sitting,” adds Diaz.
“Almost any type of exercise that gets you breathing harder and your heart
beating faster may be beneficial.”

And although occupational sitting
was less problematic, Diaz notes that the same approach to movement applies at
work. “We recognize that it isn’t easy for some workers, like truck
drivers, to take breaks from sitting, but everyone else should make a regular
habit of getting up from their desks. For those who can’t, our findings show
that what you do outside of work may be what really counts.”

The researchers suspect that the
study’s findings may be applicable to anyone who is sedentary, even though the
study focused on African Americans.

What’s Next

In future studies, Diaz will examine
why TV watching may be the most harmful sedentary behavior and whether the
timing of sedentary behavior around dinner time could be a contributing factor.

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