The influence of polysomnography on the Multiple Sleep Latency Test and other measures of daytime sleepiness.

INTRODUCTION

According to its guidelines, the Multiple Sleep Latency Test (MSLT) should be performed following an all-night polysomnography (PSG). However, the sleep quality and consequently the MSLT results may be affected by PSG and by the fact that a subject sleeps under unfamiliar conditions. The aim of this study was to examine whether PSG performed in a sleep laboratory has any influence on the MSLT and other measures of daytime sleepiness.

METHODS

Twenty healthy subjects with a mean age of 35.9+/-10.1 years underwent two MSLT examinations, and the 2 examination days were at least 4 weeks apart. In addition, on each occasion a monotonous vigilance task (VT) was performed and the subjects were asked to fill out the Epworth Sleepiness (ESS) and Visual Analogue Scales (VAS). In a cross-over design, a group of 10 subjects underwent a MSLT (MSLT-P) following a PSG and, on a second occasion, a MSLT (MSLT-N) was performed without a prior PSG. Vice versa, a second group of 10 subjects underwent first MSLT-N and then MSLT-P.

RESULTS

None of the MSLT parameters differed significantly between MSLT-P and MSLT-N. The other measures of daytime sleepiness (VT, ESS, VAS) also showed no evidence of significant differences between days with and without a prior PSG.

CONCLUSIONS

The results of MSLT and other measures of daytime sleepiness in healthy subjects are not influenced by the fact whether or not the subjects had a PSG the night prior to MSLT.