Physical exercise related improvement in obstructive sleep apnea. Look for the rostral fluid shift

Obstructive sleep apnea (OSA) is a common and underdiagnosed medical disorder. OSA is associated with the symptoms of excessive daytime sleepiness (EDS). These patients typically follow a sedentary lifestyle, and sedentary behavior is related to impaired fluid dynamics in the lower body, particularly the legs. In a supine position this fluid can move towards the neck, with a subsequent increase in upper airway (UA) resistance and UA collapse. Several studies have shown that rostral fluid shift worsens OSA; however, whether physical activity can influence this has not been tested. Physical activity related improvement in OSA severity cannot be fully explained by a weight loss in the performed studies, which is of particular importance. One of the potential additional pathways is via an improvement in leg fluid dynamics, with a subsequent decrease in the supine fluid shift toward the neck, since physical activity improves leg fluid dynamics. It is likely that patients with fluid overload states such as heart failure, chronic kidney disease and resistant arterial hypertension, as well as patients with EDS are likely to benefit the most from physical exercise in terms of better leg fluid clearance, and potentially in terms of OSA severity. However, none of the studies have directly assessed the potential effect of physical activity on the leg fluid volume, and more importantly on the supine fluid shift and OSA severity. These questions should be addressed in future studies of the effects of physical exercise on OSA severity.