The consequences of partial sleep restriction for habitual sleep duration, sleepiness and reaction time in healthy males.

Abstract Objective To investigate the effect of a reduction of approximately 25% in total sleep time (TST) on sleep parameters, sleepiness and reaction time (RT) in short, long and intermediate sleepers. Design Twenty healthy young men with a TST of ≤6 h (n = 6), between 6 h and 8 h (n = 7) and > 8 h (n = 7), respectively considered as short, intermediate and long sleepers, underwent 5 consecutive nights with an approximately 25% reduction in TST, produced by delaying their usual bedtimes. All participants were subjected to 6 consecutive nights of polysomnography and assessments of sleep, sleepiness and RT at pre- and post-sleep time. The Linear Mixed Model (LMM) was mainly used to assess the effect of the group, time, and their interaction on the main outcomes. Results Long and short sleepers showed the most significant changes regarding sleep parameters and sleepiness. However, short sleepers showed more lapses and more sleepiness. Conclusions We report novel evidence of the association between cognitive function (assessed via reaction time) and sleep restriction-related risks based on real-life since individual sleep schedules were personally determined. Both long and short sleepers showed the most significant alterations of delaying bedtime regarding sleep parameters and sleepiness. However, the short sleepers showed more sleepiness, attention lapses and increased reaction times.