The amount of fluid displaced overnight from the legs into the neck as a consequence of lying recumbent correlates with the number of apneas and hypopneas per hour of sleep (AHI). Sedentary living promotes dependent fluid accumulation in the legs that can be counteracted by venous compression of the legs (compression stockings). We hypothesized that, in non-obese sedentary men with obstructive sleep apnea (OSA), wearing compression stockings during daytime will reduce the AHI by reducing the amount of fluid available for the displacement into the neck overnight. Polysomnography and measurement of overnight changes in leg fluid volume and neck circumference were performed at baseline and after one day of legs venous compression. The median AHI decreased from 30.9 (interquartile range 19.6-60.4) to 23.4 (12.9-31.8) (P=0.016) in association with a median 40% reduction in the change in leg fluid volume (P=0.016) and a median 42% reduction in the increase in neck circumference (P=0.016). These results provide proof-of-principle that overnight fluid displacement into the neck plays a causative role in OSA.
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