Cardiorespiratory fitness, with or without CVD, tied to mortality risk for veterans
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Key takeaways:
- Changes in cardiorespiratory fitness can impact all-cause mortality risk, regardless of initial fitness.
- Data reinforce the “powerful, predictive nature” of exercise testing.
Among a cohort of veterans, changes in cardiorespiratory fitness over time reflected reciprocal changes in mortality risk, independent of other comorbidities, highlighting the role of physical activity in health outcomes, data show.
“The observation that changes in risk are proportionate to changes in cardiorespiratory fitness have clinical and public health significance because they support that mortality risk can be significantly decreased by a 1 metabolic equivalent of task increase in cardiorespiratory fitness, regardless of initial cardiorespiratory fitness status,” Peter Kokkinos, PhD, physiologist in the cardiology department at the 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 needed to modify mortality risk regardless of initial fitness status. More importantly, it provides a practical guide for clinicians, and the public in general, for improving cardiorespiratory fitness to achieve more favorable health outcomes.”
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Assessing fitness level with treadmill tests
Kokkinos and colleagues analyzed data from 93,060 adults from the Washington VA health system aged 30 to 95 years (mean age, 61 years) who completed two symptom-limited exercise treadmill tests 1 or more years apart (mean, 5.8 years). Participants had no evidence of overt CVD.
Researchers assigned participants to age-specific fitness quartiles based on peak metabolic equivalents of task (METS) achieved on the baseline exercise treadmill test. Each cardiorespiratory fitness (CRF) quartile was stratified based on CRF changes — increase, decrease, no change — observed on the final exercise treadmill test.
The findings 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 yearly mortality rate was 27.6 per 1,000 person-years.
Researchers found that changes in CRF of at least 1 MET were associated with inverse and proportionate changes in mortality risk, regardless of the baseline CRF status.
A decline in CRF of more than 2 METS was associated with a 74% increase in mortality risk (HR = 1.74; 95% CI, 1.59-1.91) for low-fit individuals with CVD, and a 69% increase for those without CVD (HR = 1.69; 95% CI, 1.45-1.96).
“The salient and unique finding of the current study is that it quantifies the volume of change in CRF needed to alter mortality risk,” the researchers wrote. “Changes in CRF of 1 MET (increases or decreases) were associated with concomitant and progressive changes in mortality risk, whereas a major portion of the risk reduction was noted with CRF changes of > 2 METS. These findings provide a guide for clinicians and the public in general regarding CRF changes necessary to improve CRF and health outcomes.”
CRF ‘vastly 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 prove once again that, despite well-established evidence, CRF remains “a vastly undervalued measure in both clinical settings and in the public health area,” and called for exercise testing to be used more routinely in care.
“These findings reinforce the powerful, predictive nature of CRF observed in previous investigations,” Kaminsky and colleagues wrote. “In fact, the prognostic utility of CRF outperforms commonly assessed clinical CVD risk factors, such as lipids, blood pressure, body habitus, smoking and blood glucose. Despite these well-documented observations, clinical settings almost exclusively use exercise testing for diagnostic purposes or organ transplant candidacy and do not take advantage of its multidimensional applications.”
The editorial noted that, due to time constraints of providers, clinical exercise physiologists would be ideal professionals to develop and implement exercise interventions for individuals with diagnosed chronic conditions or those with risk factors, respectively.
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