No negative impact of a vibro-tactile supine-avoidance alarm on sleep onset latency following supine posture shifts during sleep.

It is unclear to what extent posture shifts during sleep are associated with prior arousal and full awakening, and if supine-avoidance alarms to discourage supine sleep promote more extended wake following supine alarms. Thus, this study sought to examine relationships between posture shifts, arousals and awakenings, and to establish if a vibro-tactile supine-avoidance alarm delays the return to sleep following supine posture shifts. Detailed posture shift and sleep data from a chest-worn device with an inactive or active supine-avoidance alarm, and in-home sleep study data were from 37 participants who completed a randomised controlled trial of supine-avoidance device treatment for supine-predominant obstructive sleep apnea. Posture shifts, sleep, arousal and awakening responses, and sleep onset latency following posture shifts were compared between baseline and supine-avoidance treatment nights. Compared to baseline, there was a marked reduction in overnight supine time with active supine-avoidance treatment. Around 90% of posture shifts were preceded by either wake, arousal or full awakening. Sleep onset latency was longer for posture shifts occurring from prior wake compared to those from prior sleep but was not different between baseline or supine-avoidance treatment nights or between shifts from non-supine to supine or vice-versa. Most overnight posture shifts are associated with either prior wake or brief arousal, which likely facilitates co-ordinated body movements needed for effective posture shifts. Thus, sleep is typically already interrupted around the time that supine-avoidance alarms are activated, and the alarm itself does not significantly delay the return to sleep.