P114 Influence of sleeping position on frequency of awakenings and arousals

Abstract Introduction Little is known about the physiological and biomechanical factors that determine individual preferences in lying posture during sleep. This study investigated relationships between position preference and position specific arousals and awakenings to explore mechanisms by which biomechanical factors influence position preference. Methods 41 healthy mature aged adults (Age: 61.6 ± 5.9 years) including 25 females and 16 males, underwent two nights of home polysomnography ~2 weeks apart, on a standardised firm foam mattress, measuring sleep architecture and position. Lateral-supine ratio (LSR) was calculated for each night of sleep as: LSR=(Duration Lateral)/(Duration Supine+Duration Lateral)*100 Restlessness measures specific to lateral and supine positions including arousal frequency, and wake frequency were calculated and analysed for relationship with LSR via linear mixed effects regression. Results Wake frequency was greater in supine with greater inter-subject standard deviation (mean ± standard deviation: 4.80 ± 3.87 wakes/hr), in comparison to lateral (2.31 ± 1.05 wakes/hr). There was strong statistically significant correlation between LSR and wake frequency in supine (β = 1.9, p = 0.0013), while effect of LSR on wake frequency in lateral was weaker and not statistically significant (β = -1.1, p = 0.60). Strong significant correlation between LSR on night 1 and LSR on night 2 (β = 0.95, p < 0.001) was found indicating strong consistency in sleep preference. Discussion The findings suggest that some individuals have low tolerance to supine posture, represented by a comparatively high wake frequency in supine. These individuals compensate for high wake frequency in supine by sleeping a greater proportion in lateral.