The prognostic role of cardiopulmonary exercise testing in obesity
Audrey Borghi-Silva1, Baruch Vainshelboim2, Cássia da Luz Goulart1
1Cardiopulmonary Physiotherapy Laboratory, Physiotherapy Department, Federal University of Sao Carlos, Sao Carlos, Brazil.
Insights
Poor cardiorespiratory fitness in obese individuals is linked to increased mortality risk. Key cardiopulmonary exercise testing (CPET) variables like peak oxygen uptake (pVO2) effectively predict survival outcomes in this population.
Area of Science:
- Cardiology
- Exercise Physiology
- Obesity Medicine
Background:
- Obesity is associated with increased risk of chronic diseases.
- Cardiorespiratory fitness is a crucial factor in overall health and disease prevention.
- Cardiopulmonary exercise testing (CPET) provides valuable insights into cardiorespiratory function.
Purpose of the Study:
- To determine if key variables from CPET can predict all-cause mortality in obese individuals.
- To establish optimal cut-points for CPET variables for survival prediction.
- To investigate the association between cardiorespiratory fitness parameters and mortality risk in obesity.
Main Methods:
- Analysis of 469 obese participants (mean age 40 ± 13 years) undergoing CPET.
- Utilized receiver operating characteristic analysis to identify optimal CPET variable thresholds.
- Employed Kaplan-Meier and Cox regression analyses to assess the relationship between CPET variables and all-cause mortality.
Main Results:
- 46 deaths occurred during a mean follow-up of 69 ± 48 months (2% annual mortality rate).
- Optimal thresholds for survival prediction included peak oxygen uptake (pVO2) ≤16 mL/kg/min, VE/VCO2 slope ≥31, ventilatory power ≤5.8 mmHg, and circulatory power ≤2980 mmHg/mL O2/min.
- A pVO2 ≤16 mL/kg/min was associated with a 20-fold increased mortality risk; men had higher mortality than women.
Conclusions:
- Poorer cardiorespiratory fitness, indicated by low pVO2, ventilatory efficiency, and power indices, is strongly associated with increased all-cause mortality in obese patients.
- CPET variables are significant predictors of prognosis in individuals with obesity.
- These findings underscore the importance of assessing cardiorespiratory fitness in obesity management.
Aim:
Poor cardiorespiratory fitness has been suggested to increase the risk of chronic diseases in obesity. We investigated the ability of key variables from cardiopulmonary exercise testing (CPET) to predict all-cause mortality in an obese cohort.
Methods:
The sample included 469 participants of both sexes (mean age 40 ± 13 years) who underwent a CPET for clinical reasons between 1 March 2009 and 1 December 2023. All-cause mortality was the prognostic endpoint. A receiver operating characteristic analysis was performed to establish optimal cut-points for CPET variables. Kaplan-Meier and Cox regression analyses were used to determine the association between CPET variables and all-cause mortality.
Results:
There were 46 deaths during a mean follow-up period of 69 ± 48 months, resulting in an annual mortality rate of 2%. Despite the sample being made up of mostly women (70%), there were more deaths in men (18 vs. 6%, p < 0.001).The optimal thresholds for discrimination of survival were as follows: (a) peak oxygen uptake (pVO2) ≤16 mL/kg/min; (b) minute ventilation/carbon dioxide production (VE/VCO2) slope ≥31; (c) ventilatory power ≤5.8 mmHg; and (d) circulatory power ≤2980 mmHg/mL O2/min. Kaplan-Meier survival plots revealed a significant positive association between lower pVO2, circulatory power and ventilatory power values and survival (log-rank, p < 0.001) and higher mortality for men than women. Adjusted Cox regression models showed that a pVO2 ≤16 mL/kg/min had a 20-fold higher risk of mortality when compared with >16 mL/kg/min.
Conclusion:
Given the strong association of VO2, ventilatory efficiency, circulatory and ventilatory power with all-cause mortality, our findings support the notion that poorer cardiorespiratory fitness is associated with a poor prognosis in patients with obesity.
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