High Levels of Fitness in Young Adulthood Lowers CVD, Mortality Risk: CARDIA

Deborah Brauser

December 02, 2015

BOSTON, MA — Level of cardiorespiratory fitness (CRF) at an early age may predict long-term cardiac outcomes, new research suggests[1].

New analysis from the Coronary Artery Risk Development in Young Adults (CARDIA) study showed that participants who had higher treadmill exercise testing scores at baseline, when they were between the ages of 18 and 30 years, had significantly lower LV mass index and better"global longitudinal strain" 25 years later (P=0.02 and P<0.001, respectively).

In addition, "each additional minute of baseline exercise test duration was associated with a 15% lower hazard of death . . . and a 12% lower hazard of CVD," report the investigators, led by Dr Ravi V Shah (Beth Israel Deaconess Medical Center, Boston, MA). On the other hand, each 1 minute of exercise reduction at the 7-year follow-up was linked to 20% increased hazard of CVD and 21% increased hazard of all-cause mortality.

There were no significant associations found between fitness levels and coronary artery calcification (CAC).

Still, "regular efforts to ascertain and improve CRF in young adulthood may play a critical role in promoting cardiovascular health and interrupting early CVD pathogenesis," write the researchers.

The findings were published online November 30, 2015 in JAMA Internal Medicine.

"Draws Attention"

In an accompanying editorial[2], Drs David E Chiriboga and Ira S Ockene (University of Massachusetts Medical School, Worcester) reiterate that the study's main take-away was the importance of CRF as a CVD risk factor in a younger population not heavily researched.

"However, the findings suggest that the physiologic mechanism of the significant protective effects of CRF among younger adults . . . are related to as-yet-unclear effects on myocardial structure and function rather than a direct effect of CRF on atherosclerotic plaque development."

They note that "the surprising lack of correlation" between CRF and CAC score could be caused in part by the study's limited power, with few participant CVD events or deaths, and underlines the importance of realizing how CVD differs between older and younger ages.

"The present report draws attention to the substantive and independent value of physical activity and CRF in CVD prevention regardless of age, race, or sex, highlighting its significance as a tool for individual and population-based interventions," write the editorialists, adding that more policies promoting physical activity in this young population are needed.

Significant, Independent Associations

The investigators note that although fitness in older adults has been associated with CV outcomes, the association in young adults has not been clearly established.

CARDIA was a prospective study that included 5115 young adults enrolled at four US sites. For the current analysis, the researchers examined data on 4872 of the participants (51.3% black; mean age 24.8 years) who completed a treadmill test at baseline between March 1985 and June 1986. In secondary analysis, they also examined the 2472 participants who underwent a second treadmill test 7 years later.

Other measurements included CAC scores through computed tomography at 15-, 20-, and 25-year follow-ups and LV mass at the 5- and 25-year follow-ups. At the latter point, global longitudinal strain was also assessed.

At the final follow-up, there were 193 CVD events (4%). There were also 273 deaths (5.6%); however, 200 of these were non-CV-related.

After full adjustments, the hazard ratio (HR) for all-cause mortality was 0.85 for each minute of exercise duration that was increased at baseline (95% CI 0.80–0.91, P<0.001), and the HR for CVD was 0.88 (95% CI 0.81–0.96, P=0.002).

For each minute of exercise reduction between baseline and year 7, the HR for all-cause mortality was 1.21 (95% CI 1.07–1.37, P=0.002) and for CVD was 1.20 (95% CI, 1.06–1.37, P=0.006). It was also significantly associated with worsening global longitudinal strain, "a measure of subclinical dysfunction," note the investigators (P<0.001).

"In this large biracial cohort, CRF was significantly associated with incident CVD and all-cause mortality independently of cardiometabolic and CVD risk factors," write the researchers, adding that this shows that CRF is a modifiable, prognostic biomarker of long-term risk "with links to the development of abnormal myocardial structure and function."

However, because fitness level was not associated with CAC, "traditional indices of atherosclerotic CVD progression may not completely explain fitness-related benefits on cardiovascular health."

The study was funded by the National Heart, Lung, and Blood Institute and the Intramural Research Program of the National Institute on Aging, by grants from the National Center for Research Resources and the National Institute of General Medical Sciences, and by a Fellow-to-Faculty Award from the American Heart Association. The study authors and editorialists report no relevant financial relationships.


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