Cardiorespiratory fitness, with or without CVD, associated with mortality risk for veterans

The central theses:

• Changes in cardiorespiratory fitness can affect all-cause mortality risk, regardless of initial fitness.
• Data supports the “strong, predictive nature” of exercise testing.

In a cohort of veterans, changes in cardiorespiratory fitness over time reflected reciprocal changes in mortality risk independent of other comorbidities, underlining the role of physical activity in health outcomes, the data show.

“The observation that changes in risk are proportional to changes in cardiorespiratory fitness has clinical and public health implications, as it demonstrates that increasing cardiorespiratory fitness by 1 metabolic equivalent of a task can significantly reduce the risk of mortality, regardless of the initial cardiorespiratory fitness status.” Peter Kokkinos, PhD, Physiologist in the Department of Cardiology at Washington VA Medical Center and Professor of Kinesiology and Health and Director of the Center for Exercise and Aging at Rutgers University, and colleagues wrote. “Furthermore, it quantifies the cardiorespiratory fitness change required to modify mortality risk independent of initial fitness status. More importantly, it provides clinicians and the general public with a practical guide to improving cardiorespiratory fitness for more beneficial health outcomes.”

Assessment of fitness level with treadmill tests

Kokkinos and colleagues analyzed data from 93,060 adults from the Washington VA health system, ages 30 to 95 years (mean age 61 years), who completed two symptom-limited treadmill tests 1 or more years apart (mean 5.8 years). Participants had no evidence of overt cardiovascular disease.

The researchers assigned the participants to age-specific fitness quartiles based on the maximum metabolic equivalents of the task (METS) achieved at the baseline test on the treadmill. Each quartile of cardiorespiratory fitness (CRF) was stratified based on the CRF changes—increase, decrease, no change—observed at the final treadmill test.

The results were published in the Journal of the American College of Cardiology.

During a median follow-up of 6.3 years, 18,302 participants died. The average annual mortality rate was 27.6 per 1,000 person-years.

The researchers found that changes in CKD of at least 1 MET were associated with inverse and proportional changes in mortality risk, regardless of baseline CKD status.

A decrease in CRF by more than 2 METS was associated with a 74% increase in mortality risk (HR = 1.74; 95% CI, 1.59-1.91) for those with low fitness and cardiovascular disease and a 69% increase % associated for subjects without cardiovascular disease (HR = 1.69; 95% CI, 1.45-1.96).

“The outstanding and unique finding of the current study is that it quantifies the magnitude of change in CKD required to alter mortality risk,” the researchers wrote. “Changes in CRF from 1 MET (increase or decrease) were associated with concomitant and progressive changes in mortality risk, while much of the risk reduction was seen with CRF changes > 2 METS. These results provide guidance for physicians and the general public on the CKD changes needed to improve CKD and health outcomes.”

CRF “greatly undervalued measure”

In a related editorial Leonard A. Kaminsky, PhD, The John & Janice Fisher Distinguished Professor of Wellness and director of the Fisher Institute of Health and Well-Being at Ball State University in Muncie, Indiana, and colleagues wrote that the data again prove that, despite robust evidence, CKD remains “a grossly underestimated.” Action in both clinical and public health settings” and called for exercise stress testing to be used more routinely in care.

“These results reinforce the strong, predictive nature of CKD observed in previous studies,” wrote Kaminsky and colleagues. “In fact, the prognostic benefit of CKD surpasses commonly assessed clinical CVD risk factors such as lipids, blood pressure, body habit, smoking and blood glucose. Despite these well-documented observations, clinical settings use exercise stress testing almost exclusively for diagnostic purposes or organ transplant candidates and do not take advantage of its multidimensional applications.”

The editorial noted that due to providers’ time constraints, clinical exercise physiologists would be ideal professionals to design and implement exercise interventions for individuals with diagnosed chronic conditions or those with risk factors.

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