Abstract
STUDY OBJECTIVES: We investigated the interaction between objective sleep disturbance and obesity, sedentary lifestyle, and lung dysfunction and whether it is negatively associated with cardiorespiratory fitness. METHODS: In this community cohort study of 521 men (age 46.6 ± 7.5 years), measures of anthropometry, pulmonary function, overnight sleep polysomnography, and cardiopulmonary exercise testing were processed stepwise using structural equation modeling (SEM). RESULTS: A univariate correlation analysis was used to group the corresponding variables (in parentheses) into the following eligible latent variables for lower exercise capacity: obesity (body mass index, waist-to-hip ratio), irregular exercise, impaired lung function (predicted values of forced expiratory volume in the first second, forced vital capacity, maximal ventilatory volume, and lung diffusion capacity for carbon monoxide), disrupted sleep (total sleep time, percentage of slow-wave sleep, sleep efficiency), and sleep-disordered breathing (apnea-hypopnea index, lowest oxygen saturation, percentage of total period of oxygen saturation < 90%). Advanced SEM analyses produced a well-fitted final confirmatory model that obesity (direct strength β(d) = .366, P < .001), irregular exercise (β(d) = .274, P < .001), and impaired lung function (β(d) = .152, P < .001), with their mutual interactions, as well as disrupted sleep (β(d) = .135, P = .001) were independently and directly associated with low exercise capacity. By contrast, sleep-disordered breathing (β(d) = 0, P = .215) was related to low exercise capacity indirectly through obesity into the mutual interaction cycle of obesity, irregular exercise, and impaired lung function. Sleep-disordered breathing was robustly and mutually correlated with obesity (mutual relationship index = .534, P < .001). CONCLUSIONS: Objectively measured disrupted sleep is directly and independently associated with low exercise capacity; however, sleep-disordered breathing is indirectly mediated by obesity and mutual interactions among obesity, lung dysfunction, and sedentary lifestyle and is linked to low exercise capacity. Our findings indicate that individuals with limited exercise capacity without definite causes should undertake a sleep study, particularly in those describing symptoms of sleep-disordered breathing or insomnia.