Caffeine or melatonin effects on sleep and sleepiness after rapid eastward transmeridian travel.

We measured the effects of slow-release caffeine (SRC) and melatonin (Mlt) on sleep and daytime sleepiness after a seven-time zone eastbound flight. In a double-blind, randomized, placebo-controlled study, each of three groups of nine subjects was given either 300 mg SRC on recovery day 1 (D1) to D5 (0800) or 5 mg Mlt on preflight D-1 (1700), flight day D0 (1600), and from D1 to D3 (2300), or placebo (Pbo) at the same times. Nighttime sleep was evaluated by polysomnography and daytime sleepiness from measurements of sleep latencies and continuous wrist actigraphy. Compared with baseline, we found a significant rebound of slow-wave sleep on night 1 (N1) to N2 under Pbo and Mlt and a significant decrease in rapid eye movement sleep on N1 (Pbo) and N1-N3 (Mlt). Sleepiness was objectively increased under Pbo (D1-D6) and Mlt (D1-D3). SRC reduced sleepiness but also tended to affect sleep quality until the last drug day. In conclusion, both drugs have positive effects on some jet lag symptoms after an eastbound flight: SRC on daytime sleepiness, and Mlt on sleep.

Slow release caffeine and prolonged (64-h) continuous wakefulness: effects on vigilance and cognitive performance.

Some long work or shift work schedules necessitate an elevated and prolonged level of vigilance and performance but often result in sleep deprivation (SD), fatigue and sleepiness, which may impair efficiency. This study investigated the effects of a slow-release caffeine [(SRC) at the daily dose of 600 mg] on vigilance and cognitive performance during a 64 h continuous wakefulness period. Sixteen healthy males volunteered for this double-blind, randomised, placebo controlled, two-way crossover study. A total of 300-mg SRC or placebo (PBO) was given twice a day at 21:00 and 9:00 h during the SD period. Vigilance was objectively assessed with continuous electroencephalogram (EEG), the multiple sleep latency tests (MSLT) and wrist actigraphy. Cognitive functions (information processing and working memory), selective and divided attention were determined with computerised tests from the AGARD-NATO STRES Battery (Standardised Tests for Research with Environmental Stressors). Attention was also assessed with a symbol cancellation task and a Stroop's test; alertness was appreciated from visual analogue scales (VAS). Tests were performed at the hypo (02:00-04:00 h, 14:00-16:00 h) and hypervigilance (10:00-12:00 h, 22:00-00:00 h) periods during SD. Central temperature was continuously measured and safety of treatment was assessed from repeated clinical examinations. Compared with PBO, MSLT showed that SRC subjects were more vigilant from the onset (P=0.001) to the end of SD (P < 0.0001) whereas some cognitive functions were improved till the thirty third of SD but others were ameliorated through all the SD period and alertness was better from the thirteenth hour of SD, as shown by Stroop's test (P=0.048). We showed that 300-mg SRC given twice daily during a 64-h SD is able to antagonize the impairment produced on vigilance and cognitive functions.

Slow-release caffeine: a new response to the effects of a limited sleep deprivation.

STUDY OBJECTIVES: The aim of this study is to assess the interest of the intake of a new galenic form of caffeine called "slow-release" caffeine (SR caffeine) during a decrease of vigilance due to a limited sleep deprivation. DESIGN: The controlled method used compared three doses of SR caffeine (150, 300 and 600 mg) with a placebo. Tests were performed 2, 9 and 13 hours after each treatment. Wakefulness level was assessed subjectively through questionnaires and analog visual scales, and objectively with the Multiple Sleep Latency Test. Performance level was also assessed regularly with an attention test, a grammatical reasoning test, a spatial recognition test, a mathematical processing test, a visual tracking test, a memory search test, and a dual task. The motor activity was evaluated by wrist actimeter and safety of treatment was observed by regular clinical examination. SETTING: NA. PARTICIPANTS: Twenty-four young and healthy volunteers (12 men and 12 women) participated in a 32-hour sleep deprivation. INTERVENTIONS: NA. RESULTS: The results show a significant effect of slow-release caffeine vs. placebo, and on vigilance and performance when subjects became tired. The effects of SR caffeine lasted 13 hours after treatment. SR caffeine 300 and 600 mg are efficacious doses but the optimal dose (maximum effect without any side effects) for both men and women is after all 300 mg. Globally, there is no difference between placebo and caffeine during the recovery night period. CONCLUSIONS: SR caffeine (300 mg) seems to be an efficient and safety substance to maintain a good level of vigilance and performance during limited sleep deprivation.

Naps and modafinil as countermeasures for the effects of sleep deprivation on cognitive performance.

Disruptions in wake-sleep rhythms, particularly induced by sleep deprivation are limiting factors for military personnel in operations. The role of sleep and naps in the recovery of performance is generally accepted. Pharmacological aids, for example hypnotic or stimulant substances can also be effective countermeasures. Recently, a new stimulant compound, modafinil (MODIODAL) has also proven effective. Considering the excellent results obtained with napping and modafinil, we have studied the combined effect of these two countermeasures on psychomotor performance under conditions simulating an operational situation. Beneficial effects of a few hours' nap on performance were confirmed. Consequently naps should be encouraged, even if limited and diurnal. Modafinil, which combines wakening and stimulating properties without any known side effects, was useful for longer periods of sleep deprivation and when there was no real possibility of sleep recovery. Modafinil did not prevent sleep if sleep opportunities were available. The combination of naps and modafinil demonstrated the best cognitive performance during sleep deprivation.

[Evaluation of the attention span of 10,000 school children 8-11 years of age]. / Evaluation de la capacité d'attention chez 10,000 enfants scolarisés âgés de 8 à 11 ans.

AIM: This study was conducted in order to evaluate the attention capacity during the school day and week, taking school life and others factors into account in 10,000 children (8 to 11 years old) in public Parisian schools. MATERIAL AND METHODS: The test used to measure attention was a paper and pencil test validated from the Zazzo test. The children answered a questionnaire before each test to obtain information concerning the time and day of the test, and concerning also the different life styles of children, particularly quantity and quality of sleep and composition of breakfast. The evaluation was performed four times in the morning and four times in the afternoon every day, to measure exactly the fluctuations of attention. This study lasted four weeks. The last evaluation week took place after the summer time change. RESULTS: The results showed the existence of an ultradian fluctuation of attention during the day, with the lowest level between 08.00 a.m. and 09.30 a.m. and the highest level between 04.00 p.m. and 04.30 p.m. The attention levels on Monday and Thursday, after a day without school, were not lowered. Furthermore, after a 2 days weekend the attention level was higher than after a 1 day and half weekend. The summer time change also worsened the attention capacity of children all along the next week. Finally, there was a statistical relationship between children attention capacity and their sleep practice. CONCLUSION: These results confirm the ultradian fluctuation of attention capacity and show the importance of the regularity in the child's life style with respect to their mental functioning.

Influence of the composition of a meal taken after physical exercise on mood, vigilance, performance.

The metabolic and behavioral effects of nutrients after exercise on vigilance level, performance, and mood have been minimally studied and have given contradictory results. In order to increase the understanding of the relationships between nutrition, exercise and performance, this experiment compared the effects on mood and performance of a protein- rich meal and a protein- poor meal, eaten just after an acute session of exercise. Vigilance and mood were evaluated by visual analog scales, and memory was measured by memory search task from the AGARD STRES battery, based on the Sternberg paradigm. Forty-two subjects were involved in this experiment. All subjects participated in the study of the effect of exercise after two kinds of meals (protein and nonprotein). Two groups of fourteen subjects we used to evaluate the effect of the exercise and the effect of the delay of meal intake after exercise in the two kinds of diet. The results show no difference in memory performance between exercise and rest conditions, nor between "protein" and "no protein" meal groups. They do show, however, that subjects feel happier after a meal with protein than after a meal without protein. The effects of the "no protein" meal on drowsiness differ with the glucide content of the meal. Subjects are less drowsy when they eat between 125 and 150 g of glucide than when they eat more than 150 g. The rousing effect induced by physical exercise is counterbalanced when subjects eat more than 150 g of carbohydrate. The anxiolytic effect of glucide is re-established.

Interest of modafinil, a new psychostimulant, during a sixty-hour sleep deprivation experiment.

Modafinil, a new psychostimulant, was evaluated in eight healthy volunteers subjected to 60 hours of sleep deprivation. During continued wakefulness, vigilance was evaluated by self-assessment questionnaires, analogue visual scales, multiple sleep latency tests (MSLT), sleep logs, and continuous ambulatory electroencephalographic recordings (EEG). Modafinil (200 mg) or a placebo was given every 8 hours for three days; the sessions were separated by a 15 day wash out period. Results indicated a satisfactory level of vigilance, both subjective and objective, after the administration of modafinil, characterised by the quasi total absence of microsleep episodes which gradually occurred under placebo conditions. The confirmed wakening potency of modafinil makes this substance suitable for therapeutic use in patients with sleep disorders such as Gelineau's syndrome and hypersomnia.

Some measures to reduce effects of prolonged sleep deprivation.

Prolonged sleep deprivation is an exceptional situation, encountered in special environments such as sports, civilian and military, and which induces deficits in vigilance and performance. Among the array of measures which may be used to counteract these effects, the authors described a protocol using the combination of small naps, and administration of a pharmacological aid. A detailed description of advantages and drawbacks of each one of these measures is given, illustrated by several examples extracted from different studies. Four aspects of pharmacological aid are reviewed: the effects of amphetamines and amphetamine-like substances, caffeine, eugregoric substances, and the effect of the association small nap + eugregoric substances. The use of these various aids is discussed, and findings show that each one of them finds an application in a specific context.

Evaluation of drowsiness during prolonged sleep deprivation.

Prolonged sleep deprivation is a relatively frequent situation during military training or warfare. A 60-hour sleep deprivation experiment was carried out on eight healthy volunteers of the French Air Force to assess drowsiness. Parameters used to assess drowsiness were questionnaires on behavior, measurement of sleep latency (MSLT), continuous electroencephalogram recording, and number of response failures or control losses observed during repeated psychomotor tests. Results showed a gradual decrement in arousal in all subjects and for all tests. These results, consistent with the literature, confirm the emergence of drowsiness after the 24th hour of uninterrupted wakefulness. This phenomenon had an increasingly negative effect on performance due to "micro-sleep" episodes which substantially reduced psychomotor performance.