When it comes to being couch potatoes, Americans aren’t
alone. Physical inactivity has become a global pandemic, say researchers in a
series of related papers published in
the journal Lancet. According to one of the reports, lack of exercise causes as
many as 1 in 10 premature deaths around the world each year — roughly as many
as smoking.
About 5.3 million of the 57 million deaths worldwide in 2008
could be attributed to inactivity, the new report estimates, largely due to
four major diseases: heart disease, Type 2 diabetes, breast cancer and colon
cancer. The study finds that if physical inactivity could be reduced by just
10%, it could avert some 533,000 deaths a year; if reduced by 25%, 1.3 million
deaths could be prevented. Say we got everyone off the couch and eliminated
inactivity altogether: the life expectancy of the world’s population would rise
by about 0.68 years (more, if you discount those who were already active),
comparable to the effect of doing away with smoking or obesity.
For the study, led by I-Min Lee in the division of
preventive medicine at Brigham and Women’s Hospital, scientists calculated
something called a population attributable fraction (PAF), a measure of the
contribution of risk factors like physical inactivity to diseases such as heart
disease or diabetes, and even risk of death. The PAF told researchers how many
cases of disease could theoretically be prevented if the risk factor were
eliminated — that is, if all inactive people in a population were to start
exercising sufficiently.
Lee and his colleagues collected data on physical inactivity
and outcomes of the four major diseases — heart disease, Type 2 diabetes,
breast cancer and colon cancer — as well as rates for death from all causes.
They then calculated PAFs for 123 countries. Overall, the estimates suggest
that lack of exercise causes about 6% of heart disease, 7% of Type 2 diabetes,
and 10% of breast and colon cancers worldwide.
Exercise has long been known to can lower risk factors like
high blood pressure, high blood sugar and high cholesterol, which in turn
reduces the risk of heart disease and diabetes. Physical activity also keeps
heart vessels healthy and inhibits the formation of atherosclerotic plaques
that can cause blood clots.
As for breast cancer, exercise may protect women by reducing
fat — particularly dangerous belly fat, whose metabolic activity may trigger
tumor growth in breast tissue. Colon cancer may work differently: researchers
believe that exercise helps keep digestion regular and prevents potentially
cancer-causing waste from encouraging abnormal growths in the colon.
Current guidelines recommend that people get about 150
minutes of moderate exercise a week — a half-hour of brisk walking five times a
week would do it. But in another Lancet paper published in the series, Pedro
Hallal of the Federal University of Pelotas, in Brazil, and his colleagues found
that 31% of adults worldwide (1.5 billion people) and 4 out of 5 teens aren’t
exercising enough to meet that standard and therefore putting themselves at
risk for chronic disease.
The researchers analyzed self-reports of exercise among
adults in 122 countries, representing 89% of the world’s population, and among
teens in 105 countries. Rates of physical inactivity were higher in high-income
countries than in low-income nations. The Americas were overall the most
sedentary region — with 43% of the population not exercising enough — while
rates of inactivity were lowest in southeast Asia (17%).
One key reason is that we rely too much on modern
conveniences like cars to get around. In the U.S., for example, fewer than 4%
of people walk to work and fewer than 2% bike to commute; compare that to about
20% of people who walk to work in China, Germany and Sweden, and the more than
20% who bike their commutes in China, Denmark and the Netherlands, WebMD
reports. Add to that the inordinate time most of us spend sitting — at the
office, in front of the computer or watching TV.
Hallal estimates that sedentary people have a 20% to 30%
greater risk of heart disease and diabetes than regular exercisers. But despite
the deadly effects of lack of exercise, Hallal says physical activity doesn’t
get the same attention or funding as other health risk factors. “It gets
underfunded and undervalued,” Hallal told the Los Angeles Times. “But it’s huge
everywhere in the world.”
There was some encouraging news in the results as well:
thanks to greater awareness about the importance of physical activity in
improving health, about 31% of adults do report engaging in vigorous exercise
three or more days a week.
Another paper in the Lancet series also examined what kinds
of interventions might help people get active. Researchers analyzed 100 reviews
of clinical and community-based efforts to encourage exercise and found some
simple strategies that seemed to work: using signs to motivate people to use
the stairs instead of the elevator, for instance, or offering free exercise
classes in public places such as parks, especially geared toward women,
lower-income folks and the elderly, groups who are less likely to get the recommended
amount of exercise. Studies from the U.S., Australia, Belgium, Canada, England
and Germany indicate that maintaining streets and improving lighting can boost
activity levels by as much as 50%.
The authors of the study pointed to a particularly effective
program called Ciclovía, which started in Bogotá, Columbia, and has spread to
100 other cities in the Americas. On Sunday mornings and public holidays, the
program closes city streets to motorized vehicles, leaving roadways open for
walkers, runners, skaters and bikers. Ciclovía attracts about a million people
each week, the study notes, mostly people on lower incomes, and accounts for
14% of people’s weekly recommended exercise.
Commenting on the Lancet series, many experts agreed that
physical activity should be a global priority, though some took issue with the
comparison with smoking. In an interview with WebMD, Timothy Armstrong,
coordinator of the surveillance and population-based prevention program for the
World Health Organization, noted that if the authors of the first paper had
calculated the effects of smoking the same way they had for inactivity, the
death statistics wouldn’t be quite so similar. Further, as Dr. Claire Knight of
Cancer Research U.K. told the BBC, even if smoking and inactivity kill the same
number of people, far fewer people smoke than are sedentary, making tobacco
more risky to the individual.
Nevertheless, no one disagrees that the world population as
a whole must start exercising more — and soon. “This is a super, super
analysis,” Dr. James Levine, professor of medicine at the Mayo Clinic, told
WebMD regarding Lee’s paper in the Lancet. “We know that as soon as somebody
gets out of their chair, their blood sugar improves, their blood cholesterol
and triglycerides improve, and that’s very consistent. Every time you get up it
gets better. Every time you sit down it gets worse.”
The message, he says, is simple — get moving.
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