Objective: Obstructive sleep apnea (OSA) is associated with increased risk of adverse cardiovascular events. Because cardiopulmonary exercise testing (CPET) aids in prognostic assessment of heart disease, there is rising interest in its utility for cardiovascular risk stratifi cation of patients with OSA. However, the relationship between OSA and exercise capacity is unclear. This study was conducted to test the hypothesis that OSA is associated with impaired exercise capacity.
Methods: Fifteen subjects with moderate-to-severe OSA (apneahypopnea index [AHI] ≤ 15 events/h) and 19 controls with mild or no OSA (AHI < 15 events/h) were enrolled. Subjects underwent standard polysomnography to determine AHI and exclude other sleep disorders. Resting metabolic rate was measured via indirect calorimetry, followed by maximum, symptom-limited CPET. Subjects completed a sleep diary and physical activity questionnaire characterizing behaviors in the week prior to testing.
Results: Percent predicted peak oxygen uptake ( O2) was signifi cantly lower in OSA subjects than controls (70.1% ± 17.5% vs 83.8% ± 13.9%; p = 0.02). Each 1-unit increase in log-transformed AHI was associated with a decrease in percent predicted peak O2 of 3.20 (95% CI 0.53-5.88; p = 0.02). After adjusting for baseline differences, this association remained signifi cant (p < 0.01). AHI alone explained 16.1% of the variability observed in percent predicted peak O2 (p = 0.02).
Conclusions: OSA is associated with impaired exercise capacity. Further study is needed to evaluate the utility of CPET for prognostic assessment of patients with OSA.
- Cardiopulmonary exercise test
- Exercise test
- Exercise tolerance
- Obstructive sleep apnea
- Risk assessment