Mathias Guillard

Effect of one night of sleep loss on changes in tumor necrosis factor alpha (TNF-α) levels in healthy men

Total sleep deprivation in humans is associated with increased daytime sleepiness, decreased performance, elevations in inflammatory cytokines, and hormonal/metabolic disturbances. To assess the effects of 40 h of total sleep deprivation (TSD) under constant and well controlled conditions, on plasma levels of TNF-α and its receptor (TNFR1), interleukin-6 (IL-6), cortisol and C-reactive protein (CRP), sleepiness and performance, 12 healthy men (29±3 years) participated in a 5-days sleep deprivation experiment (two control nights followed by a night of sleep loss and one recovery night). Between 0800 and 2300 (i.e. between 25 and 40 h of sleep deprivation), a serial of blood sampling, multiple sleep latency, subjective levels of sleepiness and reaction time tests were completed before (day 2: D2) and after (day 4: D4) one night of sleep loss. We showed that an acute sleep deprivation (i.e. after 34 and 37 h of sleep deprivation) induced a significant increase in TNF-α (P<0.01), but there were no significant changes in TNFR1, IL-6, cortisol and CRP. In conclusion, our study in which constant and controlled experimental conditions were realized with healthy subjects and in absence of psychological or physical stressors, an acute total sleep deprivation (from 34 h) was sufficient to induce secretion of pro-inflammatory cytokine such as TNF-α, a marker more described in chronic sleep restriction or deprivation and as mediators of excessive sleepiness in humans in pathological conditions.

In flight automatic detection of vigilance states using a single EEG channel

Sleepiness and fatigue can reach particularly high levels during long-haul overnight flights. Under these conditions, voluntary or even involuntary sleep periods may occur, increasing the risk of accidents. The aim of this study was to assess the performance of an in-flight automatic detection system of lowvigilance states using a single electroencephalogram channel. Fourteen healthy pilots voluntarily wore a miniaturized brain electrical activity recording device during long-haul flights (10 ± 2.0 h, Atlantic 2 and Falcon 50 M, French naval aviation). No subject was disturbed by the equipment. Seven pilots experienced at least a periodofvoluntary(26.8 ± 8.0 min, n = 4)orinvoluntarysleep (N1 sleep stage, 26.6 ± 18.7 s, n = 7) during the flight. Automatic classification (wake/sleep) by the algorithm was made for 10-s epochs (O1-M2 or C3-M2 channel), based on comparison of means to detect changes in α, β, and θ relative power, or ratio [(α + θ)/β], or fuzzy logic fusion (α, β). Pertinence and prognostic of the algorithm were determined using epoch-by-epoch comparison with visual-scoring (two blinded readers, AASM rules). The best concordance between automatic detection and visualscoring was observed within the O1-M2 channel, using the ratio [(α + θ)/β] (98.3 ± 4.1% of good detection, K = 0.94 ± 0.07, with a 0.04 ± 0.04 false positive rate and a 0.87 ± 0.10 true positive rate). Our results confirm the efficiency of a miniaturized single electroencephalographic channel recording device, associated with an automatic detection algorithm, in order to detect low-vigilance states during real flights.

Sleep Extension before Sleep Loss: Effects on Performance and Neuromuscular Function.

PURPOSE This study aimed to investigate the effects of six nights of sleep extension on motor performance and associated neuromuscular function before and after one night of total sleep deprivation (TSD). METHODS Twelve healthy men participated in two experimental conditions (randomized crossover design): extended sleep (EXT, 9.8 ± 0.1 h time in bed) and habitual sleep (HAB, 8.2 ± 0.1 h time in bed). In each condition, subjects performed six nights of either EXT or HAB at home followed by an assessment of motor performance and neuromuscular function at baseline (D0) and after one night of TSD, i.e., 34-37 h of continuous wakefulness (D1). Maximal voluntary contractions with superimposed femoral nerve electrical and transcranial magnetic stimulations and stimulations on relaxed muscles were investigated before and after submaximal isometric knee extensor exercises performed until task failure. RESULTS Time to exhaustion was longer in EXT compared with HAB (+3.9% ± 7.7% and +8.1% ± 12.3% at D0 and D1, respectively). Performance at D1 decreased from D0 similarly between conditions (-7.2% ± 5.6% and -3.7% ± 7.3% in HAB and EXT, respectively). At D1, the RPE during exercise was lower in EXT compared with HAB (-7.2% ± 7.5%) with no difference at D0. No difference was observed in voluntary activation between the two conditions. CONCLUSIONS Six nights of sleep extension improved sustained contraction time to exhaustion, and this result cannot be explained by smaller reductions in voluntary activation, measured by both nerve and transcranial magnetic stimulation. The beneficial effect on motor performance in the EXT condition was likely due to reduced RPE after TSD.

Daytime microsleeps during 7 days of sleep restriction followed by 13 days of sleep recovery in healthy young adults

We investigated the consequences of sleep restriction (SR) on maintenance of wakefulness capacities and diurnal sleepiness through microsleeps monitoring. 12 healthy males (20-36 years old) were sleep restricted (4 h per night) during 7 nights followed by 13 nights of recovery sleep. Participants completed Karolinska Sleepiness Scale (KSS) and Maintenance of Wakefulness Test (MWT) at baseline (B), during SR (SR1, SR4 and SR7) and during recovery (R3 and R13), while continuously recorded for EEG analysis. During SR, MWT latencies decreased (SR7: -24.4%), whereas the number, the cumulative duration of microsleeps and KSS scores increased. Recovery nights allowed MWT latencies, KSS scores and all sleep values to return to baseline levels, while a rebound in N3, N3% and REM% sleep stages occurred. During SR, the maintenance of N3 sleep duration seems not sufficient to reduce daytime sleepiness and MWT results did not reflect the sleepiness levels characterized by persistent sleep attacks.