ANN ARBOR, Mich. – Young adults who had greater endurance in treadmill tests lived longer and were less likely to suffer heart attacks or stroke later in life, according to a study published online by JAMA Internal Medicine.
The long-term study of a large racially diverse group of U.S. adults, age 18-30, further emphasizes the importance of being physically active, and suggests drawbacks of a commonly used test to predict heart attack risk.
Exercise treadmill testing in the study consisted of as many as nine two-minute stages of gradually increasing difficulty. The study suggests each additional minute the study participant could do on the treadmill was associated with a 15 percent lower risk of death and a 12 percent lower risk of death from a heart attack or stroke.
Surprisingly, fitness was not associated with coronary artery calcification (CAC) after 25 years of follow-up. A CAC score gives an idea of the extent of atherosclerotic plaque buildup in the arteries. Doctors commonly use the score for insight into a patient’s risk for a heart condition.
“The fact that fitness was associated with outcomes but not calcium score suggests limitations of using calcium score to predict heart attack risk in young and middle-aged adults,” says study co-first author Venkatesh Murthy, M.D., Ph.D., cardiologist at the University of Michigan Frankel Cardiovascular Center and assistant professor of internal medicine at the University of Michigan.
Calcium score is a powerful tool to identify high-risk heart patients, but previous studies have examined middle-aged and older patients.
“Calcium score may not encompass all aspects of cardiovascular risk,” Murthy says. “The current study highlights the importance of fitness among young adults, decades before people develop even early signs of heart disease like coronary calcium.”
Murthy and co-authors Ravi V. Shah, M.D., of Beth Israel Deaconess Medical Center, Boston; Laura Colangelo, MS, of Northwestern University, Illinois and Joao A.C. Lima, M.D., of Johns Hopkins Medical School, Baltimore, examined changes in fitness among participants from the National Institutes of Health sponsored Coronary Artery Risk Development in Young Adults (CARDIA) study in relation to future heart disease.
The study included 4,872 adults who underwent treadmill exercise testing for baseline results in March 1985 to June 1986 and 2,472 individuals who had a second treadmill test seven years later.
During median follow-up of nearly 27 years, participant assessments included obesity, left ventricular heart mass and strain (a measure of heart muscle contraction), coronary artery calcification and deaths from cardiovascular disease.
Among the 4,872 participants, 273 (5.6 percent) died and 193 (4 percent) experienced cardiovascular disease events during follow-up. Among the deaths, 200 were not cardiovascular related and the greatest number of those, about 45 or 22.5 percent, were due to cancer.
Also, 869 of 3,067 participants (28.3 percent) had any coronary artery calcium by year 25, and 324 of 3,001 participants (10.8 percent) had left ventricular hypertrophy which is a thickening of the heart muscle.
A second treadmill assessment at seven years suggests that worsening fitness was associated with early death and cardiovascular disease. A one-minute reduction in fitness by year seven was associated with a 21 percent increased risk of death and a 20 percent increased risk of heart-related death.
“Efforts to evaluate and improve fitness in early adulthood may affect long-term health at the earliest stages in cardiovascular disease pathogenesis,” according to the study authors.
“Association of Fitness in Young Adulthood with Survival and Cardiovascular Risk,” JAMA Intern Med. Published online November 30, 2015. doi:10.1001/jamainternmed.2015.6309.
# # #