Sleep position and sleep stages: evidence of their independence.

Recently we conducted a first ontogenetic study of sleep positions in the human, which involved five groups of 10 subjects (5 males, 5 females) from each of the following age categories: 3-5 years, 8-12 years, 18-24 years, 35-45 years, 65-80 years. They slept for 4 consecutive nights in the laboratory. Sleep positions were recorded during 2 nights with super-8 time-lapse photography. In a first report we presented results showing developmental trends in sleep position shifts, position durations and in the use of prone, supine and side positions. In the current report we present results showing that there was no significant relationship between sleep stages and sleep positions in any group. Furthermore, time-series analyses revealed no consistent pattern of position sequences in any of the age groups. It is concluded that, while there are ontogenetic trends in sleep position preferences, sleep positions are independent of sleep stages and do not show consistent rhythmicity.