Prevalence of exercise intolerance and associated factors in asymptomatic adults underwent cardiopulmonary exercise testing: the role of body mass index

Abstract

Background: Obese patients commonly present reduction in cardiorespiratory fitness (CRF) compared to normal weight counterparts. Exercise intolerance (EI) is considered as peakV’O2 < 83% of predicted. Although CRF declines inversely with respect to BMI, few studies have compared the prevalence of EI according to the BMI. Moreover, whether BMI is a predictor of EI requires further elucidation. We hypothesized that the prevalence of EI is not influenced by BMI in asymptomatic adults. Purpose: To evaluate the prevalence and associated factors of EI in asymptomatic adults stratified according to BMI. Methods: We retrospectively evaluated the results of 782 adults (41± 13 years) with BMI≤ 24.99 (n= 227), 25–29.99 (n= 198), 30–34.99 (n= 155), 35–39.99 (n= 133) and ≥40 kg/m2 (n= 69). The participants underwent cardiopulmonary exercise testing (CPET) on a treadmillramp protocol. Physiological responses to the CPETwere continuously monitored using a gas analyzer. The O2 uptake (V’O2), CO2 production, minute ventilation and heart rate were measured. The prevalence of EI was calculated and compared among groups. A multivariate logistic regression was developed consideringEI as themainoutcomeandBMIas themain predictor adjusting the model for the other main cofounders. Results: Peak V’O2/kg declined significantly (p< 0.05) according to BMI (≤24.99, 37± 10; 25–29.99, 32± 9; 30–34.99, 24± 7; 35–39.99, 22± 4; ≥40 kg/m2, 18± 4mL/min/kg). Twenty percent of the participants presented EI, with no significant differences among groups according to BMI (≤24.99, 18.1%; 25–29.99, 16.2%; 30–34.99, 19.6%; 35–39.99, 25%; and ≥40 kg/m2, 20%). After multivariate logistic regression, BMI was not selected as an important predictor of EI. Age (odds ratio, 95% confidence interval: 1.028, 1.010–1.046), sex (0.610, 0.406–0.916), sedentary lifestyle (2.548, 1.661–3.909) and smoking (2.366, 1.432–3.908) were selected as significant predictors of EI. Conclusion(s): There is considerable prevalence of EI in asymptomatic adults. Our results suggest that obesity affects cardiorespiratory fitness, however, BMI is not determinant for EI. Implications: Our results suggest that physical inactivity and smoking are more important modifiable risk factors than BMI to be considered in the prevention of EI in asymptomatic adults.