Case report: menstrual-related very short REM latency in a healthy normal control.

A healthy young woman with regular menstrual cycles and no premenstrual complaints spent 2 consecutive nights in the laboratory at follicular and mid-luteal phases of her cycle. Few differences were noted in sleep parameters with the exception of rapid eye movement (REM) latency, which decreased from 62.5 +/- 0 minutes in the follicular phase to 4.0 +/- 0 minutes in the mid-luteal phase of her cycle, accompanied by an increase in percentage of REM sleep. Very little slow-wave sleep was observed in either phase of the menstrual cycle. The subject refused further study for evaluation of narcolepsy, although she reported no daytime sleepiness. If replicated, these findings suggest phase of the menstrual cycle may primarily influence REM sleep characteristics.