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Burgess, Helen J.; Eastman, Charmane I.
doi: 10.1093/sleep/29.1.25pmid: 16453978
AbstractStudy Objective:Short sleep episodes are common in modern society. We recently demonstrated that short nights reduce phase advances to light. Here we show that short nights also reduce phase delays to light.Design:Two weeks of 6-hour sleep episodes in the dark (short nights) and 2 weeks of long 9-hour sleep episodes (long nights) in counterbalanced order, separated by 7 days. Following each series of nights, there was a dim-light phase assessment to assess baseline phase. Three days later, subjects were exposed to a phase-delaying light stimulus for 2 days, followed by a final phase assessment.Setting:Subjects slept at home in dark bedrooms but came to the laboratory for the phase assessments and light stimulus.Participants:Seven young healthy subjects.Interventions:The 3.5-hour light stimulus was four 30-minute pulses of bright light (∼5000 lux) separated by 30-minute intervals of room light. The stimulus began 2.5 hours after each subject's dim-light melatonin onset, followed by a 6- or 9-hour sleep episode. On the second night, the bright light and sleep episode began 1 hour later.Measurements and Results:The dim-light melatonin onset and dim-light melatonin offset phase delayed 1.4 and 0.7 hours less in the short nights, respectively (both p ≤ .015).Conclusions:These results indicate for the first time that short nights can reduce circadian phase delays, that long nights can increase phase delays to light, or both. People who curtail their sleep may inadvertently reduce their circadian responsiveness to evening light.
Evrard, Alexis; Barden, Nicolas; Hamon, Michel; Adrien, Joëlle
doi: 10.1093/sleep/29.1.31pmid: 16453979
AbstractAbstract:Sleep deprivation for one night induces mood improvement in depressed patients, an action that probably involves the serotonergic (5-HT) system. In animals, sleep deprivation and pharmacologic treatment with antidepressants exert similar effects on 5-HT neurotransmission, notably functional desensitization of 5-HT1A autoreceptors located on 5-HT neurons in the dorsal raphe nucleus (DRN). However, in stressful conditions, corticosterone can also induce a desensitization of these autoreceptors.Study Objectives:To investigate the mechanisms of this adaptation during sleep deprivation and the possible involvement of corticosterone, we studied the effects of an 18-hour sleep deprivation, by forced locomotion, on 5-HT1A receptor-mediated firing response of DRN 5-HT neurons in transgenic mice with impaired glucocorticoid-receptor expression (GR-i) and in wild-type animals. We also examined the effects of chronic treatment with the antidepressant drug fluoxetine in the same paradigm.Measurements and Results:In both wild-type and GR-i mice, the 18hour sleep deprivation or fluoxetine treatment had no effect on the spontaneous firing of 5-HT neurons recorded under anesthesia. However, sleep deprivation decreased the potency of the 5-HT1A agonist 8-OH-DPAT to inhibit 5-HT neuronal firing in wild-type mice, whereas it had no effect in GR-i animals. Conversely, after chronic fluoxetine treatment, the induced reduction of this 5-HT1A autoreceptor-driven response was of larger amplitude in GR-i than in wild-type mice.Conclusions:These data suggest that glucocorticoid-receptor activation by corticosterone participates in the antidepressant-like adaptive changes in 5-HT1A autoreceptors in sleep-deprived mice. On the other hand, GR-i animals exhibited enhanced 5-HT1A autoreceptor desensitization induced by fluoxetine, in line with data in other animal models of depression.
Schweitzer, Paula K.; Randazzo, Angela C.; Stone, Kara; Erman, Milton; Walsh, James K.
doi: 10.1093/sleep/29.1.39pmid: 16453980
AbstractStudy Objectives:To evaluate the effects of napping, caffeine, and napping plus caffeine on performance and alertness in both laboratory and field settings.Design:(1) Laboratory Study: parallel-groups design with random assignment to 1 of 4 experimental conditions. (2) Field Study: crossover design.Setting:Sleep laboratory and field settings.Participants:(1) Laboratory Study: 68 healthy individuals; (2) Field Study: 53 shiftworkers who worked nights or rotating shifts.Interventions:(1) Laboratory Study: an evening nap opportunity before the first 2 of 4 consecutive simulated night shifts plus placebo taken all 4 nights, caffeine taken nightly, the combination of the nap and caffeine conditions, or placebo. (2) Field Study: an evening nap on the first 2 of 4 consecutive night shifts plus caffeine taken nightly versus placebo taken nightly without naps.Measurements and Results:(1) Laboratory Study: Napping, caffeine, and their combination all improved alertness and performance as measured by Maintenance of Wakefulness Test and Psychomotor Vigilance Task, but the combination of napping and caffeine was best in improving alertness. (2) Field Study: Napping plus caffeine improved performance as measured by Psychomotor Vigilance Test and decreased subjective sleepiness in individuals working the night shift.Conclusions:Napping plus caffeine helps improve performance and alertness of night-shift workers.
Adam, Martin; Rétey, Julia V.; Khatami, Ramin; Landolt, Hans-Peter
doi: 10.1093/sleep/29.1.55pmid: 16453981
AbstractStudy Objectives:To examine whether vigilant attention and sleepiness develop differently during prolonged wakefulness in young and older men.Design, Setting, and Participants:Psychomotor vigilance task (PVT) performance and subjective sleepiness were determined in 14 sessions at 3 hour intervals in healthy young (n = 12, mean age: 25.2 years, range: 21–31 years) and older (n = 11, mean age: 66.4 years, range: 61–70 years) men who were kept awake for 40 hours under continuous supervision in a sleep laboratory and on the morning after the recovery night.Measurements and Results:PVT speed, response lapses and performance variability, and subjective sleepiness were analyzed. Sleep deprivation led to reversal of an age-related difference in PVT speed at the circadian trough of performance on the morning of the second day of prolonged wakefulness (Session × Age interaction: P < .0006). Beginning after 22 hours of wakefulness, the young men also produced more lapses (P < .004), showed higher performance instability (P < .0001), and felt sleepier (P < .03) than older men, especially during the morning after the night without sleep.Conclusions:Vigilant attention is more impaired after 1 night without sleep in young men than in older men, which has important implications for the prevention of accidents associated with the loss of sleep.
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