Studies seem to show: the less sedentary we are, the longer we will live.
Here's more:
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If people need
motivation to get up from their office chairs or couches and become less
sedentary, two useful new studies could provide the impetus. One found
that sitting less can slow the aging process within cells, and the other
helpfully underscores that standing up — even if you are standing still
— can be good for you as well.
For most of us
nowadays, sitting is our most common waking activity, with many of us
sitting for eight hours or more every day. Even people who exercise for
an hour or so tend to spend most of the remaining hours of the day in a
chair.
The health
consequences of this sedentariness are well-documented. Past studies
have found that the more hours that people spend sitting, the more
likely they are to develop diabetes, heart disease and other conditions,
and potentially to die prematurely — even if they exercise regularly.
But most of these
studies were associational, meaning that they found a link between
sitting and illness, but could not prove whether or how sitting actually
causes ill health.
So for the most groundbreaking of the new studies, which was
published this month in the British Journal of Sports Medicine,
scientists in Sweden decided to mount an actual experiment, in which
they would alter the amount of time that people spent exercising and
sitting, and track certain physiological results. In particular, with
this experiment, the scientists were interested in whether changes in
sedentary time would affect people’s telomeres.
If you are unfamiliar
with the componentry of your genes, telomeres are the tiny caps on the
ends of DNA strands. They shorten and fray as a cell ages, although the
process is not strictly chronological. Obesity, illness and other
conditions can accelerate the shortening, causing cells to age
prematurely, while some evidence suggests that healthy lifestyles may
preserve telomere length, delaying cell aging.
For the new
experiment, the Swedish scientists recruited a group of sedentary,
overweight men and women, all aged 68, and drew blood, in order to
measure the length of telomeres in the volunteers’ white blood cells.
Then half of the volunteers began an individualized, moderate exercise
program, designed to improve their general health. They also were
advised to sit less.
The other volunteers
were told to continue with their normal lives, although the scientists
urged them to try to lose weight and be healthy, without offering any
specific methods.
After six months, the
volunteers all returned for a second blood draw and to complete
questionnaires about their daily activities. These showed that those in
the exercise group were, not surprisingly, exercising more than they had
been previously. But they were also, for the most part, sitting
substantially less than before.
And when the
scientists compared telomeres, they found that the telomeres in the
volunteers who were sitting the least had lengthened. Their cells seemed
to be growing physiologically younger.
Meanwhile, in the control group telomeres generally were shorter than they had been six months before.
But perhaps most
interesting, there was little correlation between exercise and telomere
length. In fact, the volunteers in the exercise group who had worked out
the most during the past six months tended now to have slightly less
lengthening and even some shortening, compared to those who had
exercised less but stood up more.
Reducing sedentary time had lengthened telomeres, the scientists concluded, while exercising had played little role.
Exactly what the
volunteers did in lieu of sitting is impossible to say with precision,
said Per Sjögren, a professor of public health at Uppsala University in
Sweden, who led the study, because the researchers did not track their
volunteers’ movement patterns with monitors. But “it’s most likely,” he
said, that “sitting time was predominantly replaced with low-intensity
activities,” and in particular with time spent standing up.
Which makes the second
new study of sedentary behavior particularly relevant. Standing is not,
after all, physically demanding for most people, and some scientists
have questioned whether merely standing up — without also moving about
and walking — is sufficiently healthy or if standing merely replaces one
type of sedentariness with another.
If so, standing could be expected to increase health problems and premature death, as sitting has been shown to do.
To find out whether
that situation held true, Peter Katzmarzyk, a professor of public health
at the Pennington Biomedical Research Center in Baton Rouge, La., and
an expert on sedentary behavior, turned to a large database of
self-reported information about physical activity among Canadian adults.
He noted the amount of time that the men and women had reported
standing on most days over the course of a decade or more and
crosschecked that data with death records, to see whether people who
stood more died younger.
The results,
published in May in Medicine & Science in Sports & Exercise,
are soothing if predictable. Dr. Katzmarzyk found no link between
standing and premature death. Rather, as he writes in the study,
“mortality rates declined at higher levels of standing,” suggesting that
standing is not sedentary or hazardous, a conclusion with which our
telomeres would likely concur.
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