YOUNG ADULT FITNESS PROTECTS
HEART HEALTH IN MIDDLE AGE
Cardiorespiratory fitness in early adulthood significantly
decreases the chance of developing high blood pressure
and diabetes -- both major risk factors for heart
disease and stroke -- in middle age, according to
a new study supported by the National Heart, Lung,
and Blood Institute (NHLBI), part of the National
Institutes of Health. Fitness also reduces the risk
for the metabolic syndrome, a constellation of factors
that includes excess abdominal fat, elevated blood
pressure and triglycerides, and low levels of the
high-density lipoprotein, the “good” cholesterol.
Further, improving fitness in healthy young adults
can cut by as much as 50 percent the risk for diabetes
and the metabolic syndrome.
The research is the first, large observational study
to look at the role of fitness on healthy young adults’
development of risk factors for heart disease. Prior
studies had examined the relationship between fitness
and death from heart disease and stroke.
Its findings appear in the December 17, 2003, issue
of The Journal of the American Medical Association.
The study was done by researchers at Northwestern
University in Chicago, Nemours Cardiac Center in Wilmington,
DE, the Kaiser Permanente Division of Research in
Oakland, CA, the University of Minnesota School of
Public Health in Minneapolis, MN, and the University
of Alabama at Birmingham.
“This study underscores the importance of both
fitness and maintaining a healthy weight in the fight
against heart disease and stroke and their risk factors,”
said NHLBI Acting Director Dr. Barbara Alving. “Americans
need to become physically active early in life and
continue to be active as they age in order to remain
as healthy as possible.”
“Given the epidemic of obesity in the United
States and the decline in people’s physical
activity, it’s important that Americans take
steps to improve their physical fitness,” cautioned
Dr. Mercedes Carnethon, Department of Preventive Medicine
at Northwestern University in Chicago. “If all
the young adults in our study had been fit, there
would have been nearly a third fewer cases of high
blood pressure, diabetes, and metabolic syndrome.”
Heart disease and stroke are the first and third leading
causes of death for Americans. Nearly 13 million Americans
have heart disease and nearly 5 million have had a
stroke.
Data came from the Coronary Artery Risk Development
in Young Adults (CARDIA) study, which began in January
1984 and ended in December 2001. The fitness study
involved 4,487 black and white men and women, who
were ages 18 to 30 at the time of their enrollment.
They participated through four clinical centers –
in Birmingham, AL, Chicago, IL, Minneapolis, MN, and
Oakland, CA. Birmingham also served as the study’s
Coordinating Center.
All participants were followed for 15 years, but 2,478
of them had their cardiopulmonary fitness tested again
after 7 years in order to measure changes in fitness.
Cardiopulmonary fitness was measured with an exercise
treadmill test, which included up to nine, 2-minute
stages of progressive difficulty. Women were classified
as “low” in fitness if they completed
less than 6 minutes of exercise and men if they completed
less than 10 minutes. Women who completed 6-9 minutes
of exercise were classified as “moderately”
fit and men if they completed 10-12 minutes. Those
who completed more exercise were classified as “highly”
fit.
- Other findings include:
- Results were the same for black and white
adults, as well as men and women.
- Those who were low or moderately fit
had twice the risk of high blood pressure,
diabetes, and metabolic syndrome as those
who were highly fit. Moreover the risk
increased directly as fitness level dropped.
- Weight gain was inversely related to fitness
over the course of the study.
- Of those who retook the treadmill test
after 7 years, the average weight gain
was about 15 pounds. The average weight
gain after 15 years was about 28 pounds.
- Those who were obese tended to be less
fit: Of those who were obese, 68 percent
were low in fitness, 29 percent were moderately
fit, and 4 percent were highly fit. Of
those who were not obese, 13 percent were
low in fitness, 36 percent were moderately
fit, and 51 percent were highly fit.
- Fitness did not protect those who were
highly fit and obese at the start of the
study from developing diabetes or the
metabolic syndrome later in life.
“The key point from this study is that the development
of risk factors for heart disease and stroke isn’t
just the natural result of aging,” said Carnethon.
“All Americans -- including women and minorities
-- can protect themselves against those risks by maintaining
their physical fitness.
“Americans don’t have to run marathons to
improve their physical fitness,” said Cheryl Nelson,
NHLBI Project Officer for the study. “They should
try to engage in at least 30 minutes of a moderate-intensity
physical activity such as brisk walking on most and, preferably,
all days of the week. Being physically active will not
only improve their fitness but also help them maintain
a healthy weight, which in turn will protect their heart
health.”
To interview an NHLBI scientist on this study, contact
the NHLBI Communications Office at (301) 496-4236 or e-mail
nhlbinews@nhlbi.nih.gov.
To interview Carnethon, contact Elizabeth Crown, University
Relations, Northwestern University, at (312) 503-8928.
NHLBI press releases and other materials are available
online at www.nhlbi.nih.gov
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