Fitness Important for Cardiovascular Health (excerpts)

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Dec. 16, 2003 — Fitness plays an important, independent protective

role in cardiovascular health, according to the results of a

longitudinal population cohort study published in the Dec. 17 issue

of The Journal of the American Medical Association.

" Numerous risk factors for cardiovascular disease (CVD), including

hypertension, diabetes, and hypercholesterolemia..., are suspected

to be influenced by fitness, and these factors may mediate the

association between low fitness and mortality, " write Mercedes R.

Carnethon, PhD, from Northwestern University Feinberg School of

Medicine in Chicago, Illinois, and colleagues. " Previous work has

demonstrated that engaging in a regular exercise program can improve

fitness. "

The Coronary Artery Risk Development in Young Adults (CARDIA) study

recruited 5,115 subjects aged 18 to 30 years from Birmingham,

Alabama; Chicago; Minneapolis, Minnesota; and Oakland, California.

Of the subjects who completed a treadmill examination at baseline

and were followed from 1985-1986 to 2000-2001, 2,478 subjects

repeated the exercise test in 1992-1993.

Compared with subjects at or above the 60th percentile on the

exercise treadmill test, subjects below the 20th percentile were

three- to six-fold more likely to develop diabetes, hypertension,

and metabolic syndrome, after adjustment for age, race, sex,

smoking, and family history of diabetes, hypertension, or premature

myocardial infarction (P < .001 for all). Adjusting for baseline

body mass (BMI) index reduced these risks to two-fold (P < .001).

Although improved fitness over seven years was associated with

decreased risk of developing diabetes (P < .04) and metabolic

syndrome (P < .001), adjusting for changes in weight reduced the

strength and significance of these associations.

Study limitations include use of treadmill test duration as an

estimate of fitness, possible practice effect on treadmill testing,

and failure to account for genetic contributions to fitness.

" Our findings demonstrate the importance of low cardiorespiratory

fitness in young adulthood as a risk factor for developing

cardiovascular comorbidities in middle age, " the authors write. " If

the association between fitness and CVD risk factor development is

causal, and if all unfit young adults had been fit, there may have

been 21% to 28% fewer cases of hypertension, diabetes, and metabolic

syndrome. Given the current obesity epidemic and observations of a

decline in daily energy expenditure in the population, improving

cardiorespiratory fitness in young men and women and developing

public health policies that encourage physical activity should be

important health policy goals. "

Fitness Important for Cardiovascular Health CME

News Author: Laurie Barclay, MD

CME Author: Désirée Lie, MD, MSEd

Authors and Disclosures

To earn CME credit, read the news brief, the paragraphs that follow,

and answer the questions below.

Release Date: December 16, 2003; Valid for credit through December

16, 2004

Credits Available

Physicians - up to 0.25 AMA PRA category 1 credit(s)

Dec. 16, 2003 — Fitness plays an important, independent protective

role in cardiovascular health, according to the results of a

longitudinal population cohort study published in the Dec. 17 issue

of The Journal of the American Medical Association.

" Numerous risk factors for cardiovascular disease (CVD), including

hypertension, diabetes, and hypercholesterolemia..., are suspected

to be influenced by fitness, and these factors may mediate the

association between low fitness and mortality, " write Mercedes R.

Carnethon, PhD, from Northwestern University Feinberg School of

Medicine in Chicago, Illinois, and colleagues. " Previous work has

demonstrated that engaging in a regular exercise program can improve

fitness. "

The Coronary Artery Risk Development in Young Adults (CARDIA) study

recruited 5,115 subjects aged 18 to 30 years from Birmingham,

Alabama; Chicago; Minneapolis, Minnesota; and Oakland, California.

Of the subjects who completed a treadmill examination at baseline

and were followed from 1985-1986 to 2000-2001, 2,478 subjects

repeated the exercise test in 1992-1993.

Compared with subjects at or above the 60th percentile on the

exercise treadmill test, subjects below the 20th percentile were

three- to six-fold more likely to develop diabetes, hypertension,

and metabolic syndrome, after adjustment for age, race, sex,

smoking, and family history of diabetes, hypertension, or premature

myocardial infarction (P < .001 for all). Adjusting for baseline

body mass (BMI) index reduced these risks to two-fold (P < .001).

Although improved fitness over seven years was associated with

decreased risk of developing diabetes (P < .04) and metabolic

syndrome (P < .001), adjusting for changes in weight reduced the

strength and significance of these associations.

Study limitations include use of treadmill test duration as an

estimate of fitness, possible practice effect on treadmill testing,

and failure to account for genetic contributions to fitness.

" Our findings demonstrate the importance of low cardiorespiratory

fitness in young adulthood as a risk factor for developing

cardiovascular comorbidities in middle age, " the authors write. " If

the association between fitness and CVD risk factor development is

causal, and if all unfit young adults had been fit, there may have

been 21% to 28% fewer cases of hypertension, diabetes, and metabolic

syndrome. Given the current obesity epidemic and observations of a

decline in daily energy expenditure in the population, improving

cardiorespiratory fitness in young men and women and developing

public health policies that encourage physical activity should be

important health policy goals. "

The National Institutes of Health partially supported this study.

The National Heart, Lung, and Blood Institute helped support Dr.

Carnethon through a career development award.

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Fitness and body mass have been implicated in the development of CVD

risk factors such as hypertension, diabetes, metabolic syndrome, and

hypercholesterolemia. One study by Petrella and colleagues,

published in the May 2003 issue of the American Journal of

Preventive Medicine, has demonstrated that engaging in regular

exercise can improve fitness. An association between mortality and

fitness has been shown in a study by Wei and colleagues, published

in the Oct. 27, 1999, issue of JAMA. But the association between

body mass and fitness and the attenuating effect of obesity on

fitness as an independent variable have not previously been fully

examined.

Physical fitness can promote muscle insulin sensitivity, transport

of glucose, autonomic function, lower heart rate, and leaner body

mass, all contributing to lower incidence of CVD risk factors.

Promoting fitness in the general population is thus of public health

importance for the prevention of CVD mortality and morbidity.

This population-based, longitudinal cohort study of healthy adults

aged 18 to 30 years in the CARDIA study examined the effect of

physical fitness and improvement in physical fitness over seven

years on the incidence of CVD risk factors. The association between

fitness and obesity on these risk factors was also examined.

The National Institutes of Health partially supported this study.

The National Heart, Lung, and Blood Institute helped support Dr.

Carnethon through a career development award