Use of Functional Aerobic Capacity Based on Stress Testing to Predict Outcomes in Normal, Overweight, and Obese Patients

Mayo Clin Proc. 2013 Dec;88(12):1427-34. doi: 10.1016/j.mayocp.2013.10.013.

Abstract

Objective: To determine the poorly studied relationship between functional aerobic capacity (FAC) as measured by treadmill stress testing and mortality in normal, overweight, and obese patients.

Patients and methods: Patients were identified retrospectively from the stress testing database at Mayo Clinic in Rochester, Minnesota. We selected 5328 male nonsmokers (mean ± SD age, 51.8±11.5 years) without baseline cardiovascular disease who were referred for treadmill exercise testing between January 1, 1986, and December 31, 1991, and classified them by body mass index (BMI) into normal-weight (18.5-24.9 kg/m(2)), overweight (25.0-29.9 kg/m(2)), and obese (≥30 kg/m(2)) categories. Functional aerobic capacity was assessed by maximal exercise test results based on age- and sex-specific metabolic equivalents, and patients were stratified into fitness quintiles. Cox proportional hazards analysis was used to determine the relationship of all-cause mortality to fitness in each BMI category.

Results: There were 322 deaths during 14 years of follow-up. After adjustment for age and exercise confounders, FAC predicted mortality in the 3 BMI groups. Hazard ratios for FAC less than 80% of predicted vs a reference group with normal BMI and fitness (FAC ≥100%) were 1.754 (95% CI, 0.874-3.522), 1.962 (1.356-2.837), and 1.518 (1.056-2.182) for the normal, overweight, and obese groups, respectively. The CIs of the hazard ratios overlapped with no statistically significant differences (P>.05).

Conclusion: A significant increase in mortality occurs with FAC below 80% of predicted for overweight and obese subjects and below 70% for normal weight subjects. Our results suggest that clinicians need not adjust the standard for low fitness in obese patients.

Keywords: BMI; CVD; ECG; FAC; HR; MET; body mass index; cardiovascular disease; electrocardiography; functional aerobic capacity; hazard ratio; metabolic equivalent.

MeSH terms

  • Adult
  • Aged
  • Body Mass Index*
  • Cardiovascular Diseases / complications
  • Cardiovascular Diseases / mortality
  • Cardiovascular Diseases / physiopathology
  • Exercise Test*
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Metabolic Equivalent
  • Middle Aged
  • Minnesota / epidemiology
  • Obesity / complications
  • Obesity / mortality*
  • Obesity / physiopathology*
  • Odds Ratio
  • Overweight / complications
  • Overweight / mortality*
  • Overweight / physiopathology*
  • Oxygen Consumption*
  • Physical Fitness
  • Predictive Value of Tests
  • Proportional Hazards Models
  • Reference Values
  • Retrospective Studies