Fitness in early adulthood is associated with lower risks for cardiovascular disease and mortality, according to data from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, published in JAMA Internal Medicine.
While higher levels of cardiorespiratory fitness (CRF) in middle-aged and older adults have been linked to decreased risk for cardiovascular disease (CVD), the relationship between fitness in young adults and CVD risk is less clear. The CARDIA study investigators sought to shed light on this subject by examining the relationship between fitness and changes in fitness in early adulthood and later cardiovascular health.
In this prospective, longitudinal cohort study conducted from 1985 through 2011, 4872 young adults, aged 18 to 30 years, recruited from 4 sites in the United States, underwent baseline treadmill exercise testing to assess CRF. The study’s primary measure of CRF was maximal exercise duration, measured in minutes. Testing took place between March 1985 and June 1986. To assess for change in CRF, a second treadmill exercise test was performed at year 7, and 2472 of the 4872 participants underwent this second test. Clinical assessments were performed at the baseline and 7-year visits.
Given the prospective nature of the study, none of the participants had clinical CVD at the study’s onset. Main outcomes and measures were the presence of coronary artery calcification (CAC), assessed using computed tomography at years 10, 15, and 25; left ventricular (LV) mass, assessed at year 5 and, along with global longitudinal strain, at year 25; and incident CVD and all-cause mortality. Participants were contacted annually to ask about hospitalizations; when indicated, medical records were obtained and events were adjudicated. Obesity, vital status, and incident CVD were also assessed at follow-up (median time: 26.9 years).
After adjusting for age, race, sex, obesity, CVD risk factors, and LV mass index, the study demonstrated that each additional minute of baseline treadmill exercise duration was associated with a 12% lower hazard of CVD (hazard ratio [HR], 0.88; 95% confidence interval [CI]; P=.002) and a 15% lower hazard of death (HR, 0.85; 95% CI, P<.001). After full adjustment, each additional minute of baseline treadmill duration was also associated with a reduction in absolute LV mass index and better global longitudinal strain; both results were significant. There was no association between exercise test duration and CAC at years 15, 20, and 25.
Change in CRF was assessed at the study’s 7-year mark and calculated by subtracting the initial treadmill exercise test duration, in minutes, from the duration at year 7. Of the 2472 individuals who underwent the second round of treadmill testing, 308 (12.5%) increased their exercise test duration by at least 1 minute. Median change in exercise duration was -1.0 minute.
After adjustment, the data demonstrated a 20% increase in incident CVD (HR, 1.20; 95% CI; P=.006), a 21% increase in all-cause mortality (HR, 1.21; 95% CI; P=.002) in long-term follow-up, and an increase in global longitudinal strain (an indicator of subclinical dysfunction) for each 1-minute reduction in treadmill exercise duration between baseline and year-7 testing. There was no association between change in CRF and the presence of CAC.
As the CARDIA authors noted, the study revealed a strong association between CRF in early adulthood and long-term mortality, and was independent of metabolic and other cardiovascular risk factors, including obesity. Fitness was associated with cardiac remodeling but not with CAC. They concluded that “efforts to evaluate and improve CRF in young adulthood may affect long-term health at the earliest stages of CVD pathogenesis,” and that traditional indicators of atherosclerotic CVD progression may not fully explain the beneficial effects of fitness on cardiovascular health.
Shah RV, Murthy, VL, Colangelo LA, et al. Association of fitness in young adulthood with survival and cardiovascular risk: the coronary artery risk development in Young adults (CARDIA) study. JAMA Intern Med. 2015. doi:10.1001/jamainternmed.2015.6309.