Background and purpose: To measure the effects of prolonged sleep extension on daytime alertness, vigilance, and mood in healthy young adults. Little research has documented the effects of increased sleep on daytime function despite a high prevalence of daytime fatigue and sleepiness in the adult population. Past extension studies report conflicting results with regard to Multiple Sleep Latency Test (MSLT) scores, vigilance, and mood ratings. No study has challenged subjects to maximum sleep extension, defined by an MSLT score of 20.
Patients and methods: Fifteen healthy college students reporting minimal daytime sleepiness were allowed to sleep as much as possible during a sleep extension period. MSLT scores, psychomotor vigilance task (PVT) reaction times, and profile of mood states (POMS) ratings were measured at baseline, mid-extension, and end-extension.
Results: There was a significant increase in both journal and actigraphy sleep totals during all extension segments (P<0.01). MSLT scores increased significantly from baseline to both mid- and end-extension (P<0.01). Five of eight tabulated PVT measures also improved significantly at mid- and end-extension with respect to baseline (P<0.05). POMS vigor and fatigue scores showed a similar improvement (P<0.01). Seven subjects achieved an MSLT score of 20. Six subjects showed substantial improvements while two subjects obtained relatively little extra sleep and showed little or no MSLT improvement. The maximum extension group displayed exceptional improvements in vigilance and POMS ratings.
Conclusions: Extended sleep leads to substantial improvements in daytime alertness, reaction time, and mood.