Abstract Mkid 120

The development of sensitive movement detectors has stimulated interest in nocturnal motility. As no first night effect (FNE) has been found in motor activity, single-night recordings have sometimes been suggested sufficient as an objective measure of sleep quality. The aim of the present study was to investigate the stability of movement based activities over a two week period. The body motility, respiratory movements, and ballistocardiogram of 16 healthy subjects were registered using the static charge sensitive bed (SCSB) across 14 consecutive nights at their homes. The automatically analyzed SCSB data were also compared to the nightly variations in subjective sleep quality. No major systematic tendencies were found in motility during the registering period, but a subjective FNE was obvious. There was great inter-subject variation in motor activity, but noteworthy intra-subject differences were also found. The correlations between subjective and objective measures across the 14 nights quite systematically indicated better subjective sleep quality as a function of low motility. A more systematic relation was revealed when the subjective evaluations of the nights representing the extremes of motor activity were compared with each other, increased activity indicating subjectively distorted sleep. Both the great interindividual differences in motility and the unsystematic but remarkable variation within subjects suggest that, at least as regards small samples of subjects, very much cannot be inferred from single-night movement recordings. Consequently, if motility is intended to be used as an indicator of sleep quality more than one recording night is often advisable in order know the individual motor baseline.