20-Year Changes in Fitness & Cardiovascular Disease Risk (CARDIA Fitness CC)

Although aerobic capacity declines with age, the contributions of increasing body fat and decreasing physical activity are not well quantified. To address this question, we examined twenty-year changes in fitness, activity and body fat in the early participants (178 men and 246 women) in the CARDIA Fitness Study (CFS), an ancillary study to the Coronary Artery Risk Development in Young Adults (CARDIA) study. CARDIA, a population-based cohort of 5,115 black and white men and women, ages 18-30 at baseline (1985-86) is a longitudinal study of the development of cardiovascular disease (CVD) risk factors and subclinical cardiovascular disease with clinical examinations at baseline, Years 2, 5, 7, 10, and 15. The CFS, running concurrently with the Year 20 CARDIA exam, measures aerobic capacity with a symptom-limited graded exercise treadmill test (GXT), using a protocol identical to that used in the baseline CARDIA exam. Change in fitness is defined as the difference between baseline and Year 20 GXT duration. Physical activity, assessed with a validated questionnaire, and body mass index (BMI), a measure of relative adiposity calculated from measured height and weight, have been obtained at all exams. The mean within-person decrease in GXT duration was 152 seconds (sd=127), representing a decline of more than one 2-minute stage or of about 2 METs in maximal workload. The decrease was greatest among the black men (mean=-196, sd=166, n=76) and least among black women (mean=-116, sd=131, n=111), the race/gender group with the lowest GXT duration to begin with. Duration decreased by >225 seconds in 25% percent of participants, while 10% had increased duration. BMI increased by a mean of 4.4 kg/m2 (sd=4.2), and physical activity declined by a mean of 68.8 exercise units (sd=310). In multiple regression analyses that adjusted for race, gender, site, and baseline duration, activity, and BMI, change in BMI accounted for x sec/kg/m2, and 16.5% of the variability, in change in fitness, while change in activity accounted for x sec/exercise unit and 4.7% of the variability. These findings suggest that physical activity and body fat, potentially modifiable factors, contribute significantly to the change in aerobic capacity over time.

PI: Dale Williams, PhD