Slow release caeine and prolonged (64-h) continuous wakefulness: eects on vigilance and cognitive performance M. BEAUMONT 1 , D. BATEJAT 1 , C. PIERARD 1 , O. COSTE 1 , P. DOIREAU 2 , P. VAN BEERS 1 , F. CHAUFFARD 3 , D. CHASSARD 4 , M. ENSLEN 3 , J. B. DENIS 2 and D. LAGARDE 5 1 Department of physiology, Institut de MeÂdecine AeÂrospatiale du Service de Sante des ArmeÂes (IMASSA), BreÂtigny sur Orge Cedex, France, 2 CPEMPN, HIA Percy, Clamart Cedex, France, 3 Nestec SA ± Nestle Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland, 4 Institut Aster, Paris, France and 5 DGA/DSP/STTC/DTSH, Arme es, France Accepted in revised form 02 July 2001; received 31 January 2001 INTRODUCTION In everyday life, prolonged sleep deprivation (SD) and wakefulness-sleep rhythm disruptions occur frequently. These situations often lead to an impairment of vigilance and performance, which in turn lead to a decrease in ecacy (Cajochen et al. 1995; Lagarde and BateÂjat 1994; Linde and BergstroÈm 1992; Lorenzo et al. 1995). The degradation in alertness and performance which occurs during the early morning hours can be alleviated by the ingestion of psycho- stimulants such as caeine (Bonnet and Arand 1992, 1994; Bonnet et al. 1995; Linde 1994; Lorist et al. 1994; Muelbach and Walsh 1995; Walsh et al. 1990). However, the results obtained with the use of caeine to enhance vigilance and performance level vary greatly. Sometimes, the results are very positive; an increase in performance mainly in visual vigilance tasks (Fine et al. 1994) can be observed as well as an increase Correspondence: Dr Maurice Beaumont, Department of Physiology, Imassa, BP No. 73, F-91223 BreÂtigny-sur-Orge Cedex, France. Tel.: 33-1-69883321; fax: 33-1-69883302; e-mail: mbeaumont@imassa.fr J. Sleep Res. (2001) 10, 265±276 SUMMARY 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 eciency. This study investigated the eects of a slow- release caeine [(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. KEYWORDS cognitive performance, sleep deprivation, slow release caeine, vigilance Ó 2001 European Sleep Research Society 265