January 23, 2008 - One of the largest studies ever to link exercise capacity to mortality risk should motivate physicians to pay as much attention to patients' exercise capacity as they do other major risk factors, researchers say [1]. Their study of older male veterans suggests that the adjusted risk of dying was reduced by 13% for every 1 metabolic equivalent (MET) increase in exercise capacity; men with the greatest exercise capacity reduced their mortality risk by 70%. "For a little bit of investment you get a lot of a return," lead author on the study, Dr Peter Kokkinos (Veterans Affairs [VA] Medical Center, Washington, DC) told heartwire. "In a time where health insurance in this country is going through the roof, we could do something like walk for thirty minutes a day and reap major benefits. "For god's sake, if we could walk on the moon we can certainly walk on earth." Their study appears in an early online edition of Circulation,
January 22, 2008. Kokkinos and colleagues followed 15,660 male veterans with and without cardiovascular (CV) disease who had completed an exercise treadmill test at study outset. More than 40% of veterans participating in the study were black. Baseline exercise capacity for the entire group was divided into quartiles and assessed in relation to all-cause mortality over a mean of 7.5 years. Fitness reduces death-risk in dose-response fashion Kokkinos et al report that every 1-MET increase was associated with a reduction in mortality that ranged from 12% in white participants to 15% in black participants, after adjusting for age, body mass index (BMI), CV risk factors, and CV medications. Compared to veterans in the lowest fitness category (< 5 METS), those in the highest exercise capacity (> 10 METS) had a 70% lower risk of all-cause death. Even men in the moderate fitness category (7.1 - 10 METs) had a 50% lower death rate than men with the lowest fitness capacity. To heartwire, Kokkinos emphasized that the study extends findings from other studies that have largely been conducted in white subjects, from higher socioeconomic classes, to a mixed race, lower socioeconomic group who may not always have access to the best, most expensive, medical care. "No one study has all the answers, but this study fills in a lot of blanks," Kokkinos said. "The major finding is that for all sorts of people, as one increases his exercise capacity based on an exercise treadmill test, there is an inverse drop in risk in a dose-response fashion. And whether you looked at blacks versus whites, or those with heart disease versus those with no heart disease, those taking beta blockers or no beta blockers, the drop can range anywhere from
12 - 15%." The authors point out that treadmill tests is a "standardized procedure used throughout the world," but physicians may under-estimate its prognostic capacity. The study results also underscore, once again, the importance and pay-off of regular exercise. Those pay-offs may be particularly relevant in a group that, studies show, frequently cannot afford expensive medications, health club memberships, or even foods that would help improve their cardiovascular risk profile. Daily walking, by contrast, is free. "People are people, and we all get caught up in the excuse, 'I can't exercise I don't have time,'" Kokkinos commented. "But everyone needs to get involved to get this nation going again, because we are the fattest nation, the most sedentary nation in the world. And we need to do something about it." Source

1. Kokkinos P, Myers J, Kokkinos JP, et al. Exercise capacity and mortality in black and white men. Circulation 2008; DOI: 10.1161/CIRCULATIONAHA.107.734764. Available at: http://circ.ahajournals.org.

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Clinical Context

The fitness status of an individual is inversely and strongly related to cardiovascular (CV) and
all-cause mortality in healthy individuals and those with CV disease, based on studies in individuals in middle and upper income groups, but the usefulness of fitness as a predictor of mortality has not been fully examined by racial difference. The VA system provides equal access to care for veterans, and prognostic data can be compared among different racial groups without the confounder of care access. This is a longitudinal study of black and white veterans presenting to 2 VA centers for an exercise test to compare the value of exercise capacity in the prediction of CV and all-cause mortality for 7.5 years.

Study Highlights

• Included were 15,660 male veterans who presented for symptom-limited exercise tolerance tests to evaluate for ischemic heart disease at 1 of 2 centers in Washington, DC, or Palo Alto, California.
• Excluded were those with an implanted pacemaker, left bundle branch block during testing, emergent intervention, and impaired chronotropic response.
• 6749 participants were black and 8911 were white.
• Those with CV disease at baseline were defined as those with a history of myocardial infarction (MI), angiographically documented disease, coronary angioplasty, bypass surgery, chronic heart failure, or congestive heart failure.
• Death rates were recorded from the VA Beneficiary Identification and Record Locator System and from the Social Security Death Index.
• Exercise capacity in METs was estimated with a Bruce protocol based on American College of Sports Medicine equations for the ramp protocol, and subjects exercised to volitional fatigue.
• Medications were not changed.
• ST-segment depression was measured visually, and 1 mm or more of horizontal or sloping depression was considered suggestive of ischemia.
• 4 fitness categories were determined: those who achieved less than 5 METs were low fitness (n = 3170); 5 to 7 METs, moderate fitness (n = 5153); 7.1 to 10 METs, high fitness (n = 5075); and more than 10 METs, very high fitness (n = 2261).
• Mean age of participants was 59 years, mean BMI was 28.3 kg/m², mean resting heart rate was 73 beats/minute, mean resting systolic and diastolic blood pressure was 133/81 mm Hg, and one third were obese.
• Of the total cohort, one third had baseline CV disease; 40.3%, previous MI; and about half, hypertension. 12.9% whites and 23.6% blacks had diabetes.
• Mean follow-up was 7.5 years.
• 3912 deaths occurred with an annual mortality of 3.3%.
• 80% achieved a peak heart rate at least 85% of predicted.
• Men in the high fitness category were younger with a lower BMI.
• Blacks were younger than whites (58 vs 60 years) with higher systolic and diastolic blood pressure and were more likely to smoke, have CV disease, diabetes, and obesity.
• Exercise capacity was the strongest predictor of mortality (hazard ratio [HR], 0.87) followed by age (HR, 1.04), CV risk factors (HR, 1.16), and BMI (HR, 0.96).
• There was a 13% reduction in mortality risk for every 1-MET increase in exercise capacity (HR, 0.87).
• Findings were similar in those taking beta-blockers.
• The mortality reduction was 14% for blacks and 12% for whites (not significantly different) for each 1-MET increase in capacity.
• A MET level of 7.0 was the optimal threshold for increased risk for mortality; those below this threshold had a 2.6-fold increase in risk for mortality.
• Findings were similar for those with and without CV disease. In those without CV disease, the optimal threshold for increased risk for mortality was 6.0 METs (sensitivity 70%, specificity 60%).
• A 2.3-fold increase in risk for mortality was noted in those below this threshold.
• The relative risk for mortality was progressively lower at higher exercise capacity (0.80 for
  5 - 7 METs, 0.51 for 7.1 - 10 METs, and 0.31 for > 10 METs).
• The findings were similar for blacks and whites.
• Across categories by CV or no CV disease, mortality risk also decreased as exercise capacity improved.
• The mortality risk was 50% lower for both blacks and whites who achieved a capacity of
  7 to 10 METs vs those who achieved less than 5 METS regardless of CV status.
• They recommended that clinicians give attention to exercise capacity as a major risk factor.

Pearls for Practice

• Exercise capacity is a good prognostic predictor for all-cause mortality in black and white individuals regardless of CV status.
• Other predictors of mortality in black and white men are age, CV risk factors, and BMI.