ABSTRACT
In an attempt to study the relationship between sleep postures and sleep parameters assessed by actigraphy, we applied the newly developed Activity Monitoring and Evaluation System (A-MES) and actigraphy at the same time to younger and senior Japanese volunteer groups. It was found that sleep postures and diurnal activity determines, to some extent, sleep parameters including activity mean score (AMS), activity index (ACTX), waking episodes (WEP) and sleep fragmentation index (SFX). It was also found that sleep properties are different in younger and senior Japanese. For example, increase in the proportion of time in the supine position resulted in enhancement and deterioration of the sleep in the younger and senior groups, respectively. Furthermore, there were correlations between supine posture and AMS, ACTX, SFX, total minutes scored as awake (TMSA) and WEP obtained by actigraphy in the younger group, but only AMS and ACTX in senior group. In addition, we also assessed sleep parameters by use of questionnaires, and found that objective sleep quality was rather poor but subjective sleep quality was better in the senior group. In the younger group, in contrast, objective sleep quality was better but subjective sleep quality was poor. On the other hand, there was no correlation between sleep parameters assessed by actigraphy and self-report at all. The present study with A-MES and actigraphy provides the first evidence that sleep posture affects sleep quality and is a convenient, inexpensive and home-based method for studying sleep.