CURB SITTING TIME TO POSSIBLY EXTEND LIFESPAN
Reducing sedentary
activity appears to lengthen telomeres, which sit on the end of chromosomes,
the DNA storage units in each cell, the findings show
Telomeres are
important because they stop chromosomes from 'fraying' or clumping together and
'scrambling' the genetic codes they contain, performing a role similar to the
plastic tips on the end of shoelaces, to which they have been likened.
Longevity and a
healthy lifestyle have been linked to telomere length, but whether physical
activity can make any difference, is not clear.
The researchers
therefore analysed the length of chromosomal telomeres in the blood cells of 49
predominantly sedentary and overweight people in their late 60s, on two
separate occasions, six months apart.
All 49 participants
had been part of a previously reported clinical trial in which half of them had
been randomly assigned to a tailored exercise program over a period of six
months, and half had been left to their own devices.
Levels of physical
activity were assessed using a seven day diary and a pedometer to measure the
number of footsteps taken every day, while the amount of time spent sitting
down each day was gleaned through a validated questionnaire.
The time spent
exercising as well as the number of steps taken daily increased significantly
in the group following the exercise program, while the amount of time spent
seated fell in both groups.
Various risk factors
for heart disease and stroke also improved in both groups, particularly those
on the exercise program, who also lost a great deal more weight than their
counterparts left to their own devices.
But increases in
physical activity seemed to have less of an impact than reductions in sitting
time, the findings showed.
The number of daily
steps taken was not associated with changes in telomere length, while an
increase in moderate intensity physical activity was linked to a shortening in
telomere length, although this was not significant.
But a reduction in the
amount of time spent sitting down in the group on the exercise program was
significantly associated with telomere lengthening in blood cells.
"In many
countries formal exercise may be increasing, but at the same time people spend
more time sitting," write the researchers. "There is growing concern
that not only low physical activity...but probably also sitting and sedentary
behaviour is an important and new health hazard of our time."
They admit that their
study is small, and caution that it needs to be repeated in other larger
groups, and in other tissues, such as skeletal muscle and fat cells.
But they say that
their findings corroborate other research on the impact of time spent sitting
down, and conclude: "We hypothesise that a reduction in sitting hours is
of greater importance than an increase in exercise time for elderly risk
individuals."
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