Preventive Cardiology

Small Cardiorespiratory Fitness Changes, Big Mortality Impact

A new JACC study highlighted the massive impact cardiorespiratory fitness (CRF) has on mortality risks, including even small CRF changes.

The researchers had 93k VA patients (30-95yrs old, 61yrs avg, just 5.4% female) without signs of overt CVD perform two treadmill tests at least one year apart (avg. 5.8yrs apart), assigning each participant an age-specific peak metabolic equivalent value (MET) for both tests. 

They then organized the participants into four age-specific MET quartiles based on their first treadmill test (Quartile 1 = least fit; Quartile 4 = most fit), and further organized them based on MET changes in the second test (29% increased/improved, 46% decreased/deteriorated, 25% no change).

Over the study’s 6.3-year median follow-up period, 18,302 participants died, and MET changes were highly associated with those deaths.

  • Low-Fit individuals in Quartiles 1 and 2 had 60% and 76% higher mortality risks if their CRF decreased by more than two METs, but 33% and 36% lower risks if their CRF improved by more than two METs.
  • Moderate-Fit participants in Quartile 3 faced 55% higher mortality risks if their CRF decreased by more than two METs, and 39% lower risks if their CRF improved by more than two METs.
  • High-Fit individuals in Quartile 4 were best positioned. They saw an insignificant increase in mortality risk (+27%) if their CRF fell by more than two METs, and enjoyed the greatest mortality risk reduction (-43%) if their CRF improved by over two METs.

These changes were consistent across participants with and without CVD, and among individuals with smaller <2 MET changes.

In other words, it’s much better to start off in good shape, but future mortality risks are heavily influenced by whether and how much an individual’s cardiorespiratory fitness improves or deteriorates over time. In fact, comments on this study suggest that CRF is a better predictor of mortality than the CVD risk factors that we usually focus on (e.g. lipids, blood pressure, smoking, etc.) and exercise might have a greater impact than any pharmaceutical or therapy.

The Takeaway

Sometimes it takes a study like this to reinforce what most Cardiac Wire readers already know: cardiorespiratory fitness has a major impact on mortality risks and even small fitness improvements (or deteriorations) can make a big difference. It also suggests that because something as easy and economical as a 30 minute walk can have such a major impact, it might deserve a greater role in patient conversations and care plans.

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