Physiological correlates to spontaneous physical activity variability in obese patients with already treated sleep apnea syndrome.

Abstract

Physical activity is promoted in patients with sleep disorders and obesity. The aim of the present study was to assess physiological factors influencing objectively measured spontaneous physical activity in already treated patients for obstructive sleep apnea (OSA) by nocturnal continuous positive airway pressure (CPAP). Fifty-five patients (age=53±3years; body mass index (BMI)=38±3kg/m2; compliance with CPAP >4h/night) were prospectively included. Measurements were 5-day actigraphy with metabolic equivalent of task (METs) assessment, body composition, pulmonary function, quadriceps and respiratory muscle strength, exercise capacity (6-min walking distance and maximal aerobic capacity), as well as sleep parameters (sleepiness, duration, oxygen saturation, and micro-arousals during sleep) and quality of life (SF-36 questionnaire). As expected, the number of steps per day (6879±2511) and mean intensity of physical activity (1.38±0.15 METs) were below the recommendations for obese population. In age-adjusted stepwise regression models, peak oxygen consumption (VO2 peak) and peak dyspnea perception during incremental exercise test were independent predictors of the number of steps per day (r=0.49, p=0.001) although VO2 peak and peak minute ventilation were independent predictors of intensity of physical activity (in METs/day; r=0.49, p=0.001). In severe obese patients with OSA, exercise capacity, ventilatory requirement, and dyspnea perception were main physiological components of physical activity. These results emphasize the need to consider specific training interventions that increase ability to perform intense physical activity in obese OSA.