If you increase your heart rate, will your life span follow?
That possibility is at the heart of an ambitious new study
of exercise and mortality. The study, one of the largest and longest-term
experimental examinations to date of exercise and mortality, shows that older
men and women who exercise in almost any fashion are relatively unlikely to die
prematurely. But if some of that exercise is intense, the study also finds, the
risk of early mortality declines even more, and the quality of people’s lives
climbs.
اضافة اعلان
Scientists have known for some time, of course, that active
people tend also to be long-lived people. According to multiple past studies,
regular exercise is strongly associated with greater longevity, even if the
exercise amounts to only a few minutes a week.
But almost all of these studies have been observational,
meaning they looked at people’s lives at a moment in time, determined how much
they moved at that point, and later checked to see whether and when they died.
Such studies can pinpoint associations between exercise and life spans, but
they cannot prove that moving actually causes people to live longer, only that
activity and longevity are linked.
To find out if exercise directly affects life spans,
researchers would have to enroll volunteers in long-term, randomized controlled
trials, with some people exercising, while others work out differently or not
at all. The researchers then would have to follow all of these people for
years, until a sufficient number died to allow for statistical comparisons of
the groups.
Such studies, however, are dauntingly complicated and
expensive, one reason they are rarely done. They may also be limited, since
over the course of a typical experiment, few adults may die. This is
providential for those who enroll in the study but problematic for the
scientists hoping to study mortality; with scant deaths, they cannot tell if
exercise is having a meaningful impact on life spans.
Those obstacles did not deter a group of exercise scientists
at the Norwegian University of Science and Technology in Trondheim, Norway,
however. With colleagues from other institutions, they had been studying the
impacts of various types of exercise on heart disease and fitness and felt the
obvious next step was to look at longevity. So, almost 10 years ago, they began
planning the study that would be published in October in The BMJ.
Their first step was to invite every septuagenarian in Trondheim
to participate. Mortality studies involving older people are the most likely to
return useful data, the scientists reasoned, since, realistically, there will
be more deaths among the elderly than the young, making it possible to compare
differences in longevity between study groups.
More than 1,500 of the Norwegian men and women accepted.
These volunteers were, in general, healthier than most 70-year-olds. Some had
heart disease, cancer or other conditions, but most regularly walked or
otherwise remained active. Few were obese. All agreed to start and continue to
exercise more regularly during the upcoming five years.
The scientists tested the subjects' current aerobic fitness
as well as their subjective feelings about the quality of their lives and then
randomly assigned them to one of three groups. The first, as a control, agreed
to follow standard activity guidelines and walk or otherwise remain in motion
for half an hour most days. (The scientists did not feel they could ethically
ask their control group to be sedentary for five years.)
Another group began exercising moderately for longer
sessions of 50 minutes twice a week. And the third group started a program of
twice-weekly high-intensity interval training, or HIIT, during which they
cycled or jogged at a strenuous pace for four minutes, followed by four minutes
of rest, with that sequence repeated four times.
Almost everyone kept up their assigned exercise routines for
five years, an eternity in science, returning periodically to the lab for check-ins,
tests and supervised group workouts. During that time, the scientists noted
that quite a few of the participants in the control had dabbled with
interval-training classes at local gyms, on their own initiative and apparently
for fun. The other groups did not alter their routines.
After five years, the researchers checked death registries
and found that about 4.6 percent of all of the original volunteers had died
during the study, a lower number than in the wider Norwegian population of
70-year-olds, indicating these active older people were, on the whole, living
longer than others of their age.
But they also found interesting, if slight, distinctions
between the groups. The men and women in the high-intensity-intervals group
were about 2 percent less likely to have died than those in the control group,
and 3 percent less likely to die than anyone in the longer, moderate-exercise
group. People in the moderate group were, in fact, more likely to have died
than people in the control group.
The men and women in the interval group also were more fit
now and reported greater gains in their quality of life than the other
volunteers.
In essence, said Dorthe Stensvold, a researcher at the
Norwegian University of Science and Technology who led the new study, intense
training — which was part of the routines of both the interval and control
groups — provided slightly better protection against premature death than
moderate
workouts alone.
Of course, exercise was not a panacea, she adds. Some people
still sickened and died, whatever their
workout program. (No one died while
exercising.) This study also focused on Norwegians, who tend to be
preternaturally healthy, and most of us, perhaps regrettably, are not
Norwegians. We also may not yet be in our 70s.
But Stensvold believes the study’s message can be broadly
applicable to almost all of us. “We should try to include some exercise with
high intensity,” she said. “Intervals are safe and feasible for most people.
And adding life to years, not only years to life, is an important aspect of
healthy aging, and the higher fitness and health-related quality of life from
HIIT in this study is an important finding.”
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