Shorter REM latency associated with more sleep cycles of a shorter duration in healthy humans

A significant association between rapid eye movement (REM) sleep latency an d the number of non-REM/REM sleep cycles was found 15 years ago in a large retrospective study. The present prospective study further explored this in tra-sleep relationship and analyzed the links between these two variables a nd the mean cycle duration. It was based on a carefully selected group of h ealthy control subjects whose sleep was polysomnographically recorded at ho me for 4 sequential nights. The latency of REM sleep was inversely correlat ed with the number of cycles and positively correlated with the mean cycle duration, both in individual nights and on means of 4 nights. The present s tudy demonstrated that variations in the number of cycles or the mean cycle duration between the nights are far less important than the substantial di fferences observed between subjects. Present outcomes support the study of sleep cycle periods and frequencies in those psychiatric disorders where RE M sleep latencies have been found to be shorter, and they suggest that thes e variables be included in sleep studies in which cycles are compared with each other. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.