Abstract 16413: Results of Treadmill Stress Testing Need Not be Interpreted Differently for Predicting Mortality in Obese Patients
Background: Reduced functional aerobic capacity (FAC) as measured by treadmill stress testing predicts mortality in normal weight persons. The relationship between FAC and mortality in the obese, however, is unclear. We assessed the hypothesis that obese patients compared to their non-obese counterparts require a more liberal cutoff for FAC for accurate prognostication of mortality.
Methods: 5328 non-smoking men (average age, 51.8 ± 11.5 years) without baseline cardiovascular disease referred for treadmill exercise testing during 1986–1991 were classified by body mass index (BMI) into normal weight (18.5–24.9), overweight (25.0–29.9), and obese (30 kg/m2) categories. BMI groups were adjusted for inconsistency with body fat measurements. FAC was assessed by maximal exercise test based on age and gender specific metabolic equivalents (METs), 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 189 deaths during an average 16.4 ± 2.6 years of follow-up (minimum of 14 years). After adjustment for age and exercise confounders, FAC similarly predicted mortality in the three BMI groups. Hazard ratios for FAC < 80% of predicted versus a referent group with normal fitness (FAC ≥ 100%) and normal weight were 1.939 (95% confidence interval 0.999 – 3.762), 2.760 (1.808 – 4.213), and 2.408 (1.615 – 3.591) for the normal, overweight, and obese groups, respectively. Differences in hazard ratios among BMI groups were not statistically significant (p > 0.05).
Conclusion: A significant rise in mortality occurs with FAC falling below 80% of predicted for all BMI groups (Figure). Our results suggest that clinicians need not adjust the standard for low fitness in obese patients. Poorer performance on the treadmill due to excess weight appears to be balanced by the increased mortality associated with obesity.
- © 2010 by American Heart Association, Inc.