Original ArticleCardiorespiratory response to exercise in men and women with obstructive sleep apnea
Introduction
Obstructive sleep apnea (OSA) is a common condition caused by an intermittent collapse of the upper airway during sleep that results in repetitive hypoxemia and nighttime arousals, poor sleep quality, and excessive daytime somnolence. OSA has been named a risk factor for a number of cardiovascular conditions, such as arterial hypertension [1], [2], congestive heart failure [3], and stroke [4], and has been associated with increased cardiovascular mortality [5]. Physical exercise poses significant stress for the cardiovascular and pulmonary system and often leads to early diagnosis of cardiovascular (CV) abnormalities, such as coronary artery disease or cardiac arrhythmias [6], [7], [8].
OSA severity has been associated with self-reported lack of exercise, independent of body habitus, after adjusting for body mass index (BMI) [9]. OSA subjects are frequently overweight and often complain of fatigue and exercise intolerance, yet it is not clear whether OSA impairs exercise performance. A significant decrease in peak oxygen consumption was noted in patients with moderate to severe OSA in some studies [10], [11], [12], while, in others, the exercise performance of OSA subjects was normal [13], [14]. Most of the research has been done with men recruited from sleep clinics. There are limited data on the exercise performance of women with OSA or on cardiovascular response to exercise for men and women with OSA.
The aim of this study was to assess exercise performance in a prospective, consecutive sample of men and women with OSA to compare cardiorespiratory parameters, blood pressure, and heart rate responses during and after exercise.
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Subjects
Patients eligible were those subjected to polysomnography at the Sleep Institute Universidade Federal de São Paulo (UNIFESP) due to clinical suspicion of OSA with an apnea hypopnea index (AHI) > 5. A total of 108 patients with AHI > 5 were consecutively selected in March and April 2006, and 68 of them agreed to participate. Subjects were included if they were over 18 years old, sedentary, capable of performing a treadmill test, and reported no recent hospitalization or change in medication.
Results
Sixty-two subjects (32 men) completed the protocol. Six subjects were excluded: four because of poorly controlled hypertension, one because of musculoskeletal disease, and one because of morbid obesity. Their baseline characteristics are presented in Table 1. There were no differences between men and women in age, BMI, ESS, AHI, and resting systolic and diastolic BP. Spirometry variables [FEV1 (L) and FVC (L)] differed in men and women, but not from the predicted percentage as expected. The
Discussion
We analyzed cardiopulmonary exercise behavior in men and women with OSA. The main finding of this study was an association between exercise performance and AHI in women but not in men in the absence of heart or lung disease. This finding suggests a gender difference in exercise performance in patients with OSA.
OSA is a recognized risk factor for certain cardiovascular disorders, such as arterial hypertension [2], [1], heart failure [21], cardiac arrhythmias [22], [23], metabolic syndrome [24],
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