Unfit Today, Heart Trouble Tomorrow

Young treadmill dropouts at much higher risk

TUESDAY, Dec. 16, 2003 (HealthDayNews) -- Young adults who can't complete a treadmill test of fitness are more likely to develop risk factors for heart disease and stroke in the years ahead than those who go closer to the full course, researchers report.

It's a standard test often used to assess fitness in older people, says Mercedes R. Carnethon, an associate professor of preventive medicine at Northwestern University's Feinberg School of Medicine and lead author of a report in the Dec. 17 Journal of the American Medical Association. People start walking on a level treadmill whose speed and incline are gradually increased to a 2-degree elevation and 3 miles per hour after 18 minutes.

Carnethon and her associates had 5,115 men and women aged 18 to 30 take the treadmill test in 1985 and 1986. The 20 percent of participants who quit soonest because the effort was too much for them were three to six times more likely to develop diabetes, high blood pressure and other risk factors for heart attack and stroke over the next 15 years than those who completed at least 60 percent of the test, the study finds.

In a cautiously phrased assessment, the journal report says that "if the association between fitness and cardiovascular disease risk factor development is causal, and if all unfit young adults had been fit," there would have been 21 percent to 28 percent fewer people who developed those risk factors.

Carnethon says she can't recommend use of the treadmill test as a screening tool for future problems "based on this one observational study."

"The really meaningful issue here is that relative risk can be detected in healthy young adults, and that physical fitness is a modifiable risk factor," she says. "There is something people can do to modify that risk."

"I'm not surprised," says Dr. Henry C. McGill Jr., a professor emeritus of medicine at the University of Texas Health Science Center in Dallas who has done a lot of work on the subject. "All this reminds us in spades about what we have written about needing to develop a healthy lifestyle in childhood."

There has been a debate about the value of screening for high cholesterol levels early in life, but that has just complicated a relatively simple issue, McGill says.

"The real issue is not screening for cholesterol but making a healthy lifestyle for children," he says.

Different measures are needed, individual by individual, McGill says.

"If a child is smoking, the first thing to do is to get rid of the smoking," he says. "If the child is fat, you need to take care of that. Measuring cholesterol is a third-level issue, because that is a more difficult problem to manage."

Given "the current obesity epidemic and observations of a decline in daily energy expenditure in the population," Carnethon and her colleagues write, "policies that encourage physical activity should be important health policy goals."

"There are a lot of good reasons besides preventing heart disease to emphasize fitness," McGill adds.

More information

The American Heart Association describes the importance of physical activity for children, while the American Council on Exercise has information for people of all ages.

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