***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Thirty healthy volunteers were r and omly assigned to either a caffeine or a placebo group to investigate the alerting effects of caffeine at night . Subjects adhered to a simulated night-shift schedule for 5 consecutive nights . On the first 3 nights , 2 mg/kg caffeine was added to decaffeinated coffee at 2220 and 0120 hours for the caffeine group . On nights 4 and 5 both groups received placebo . Each night , subjects completed five 60-minute sessions of a computerized simulated assembly line performance task ( SALT ) , a multiple sleep latency test ( MSLT ) and question naires . Daytime sleep was recorded in the laboratory between 0900 and 1700 hours each day following nighttime testing . Caffeine decreased physiological sleep tendency on the night shift compared with placebo ; however , the two groups performed at equivalent levels on the SALT . On nights 4 and 5 , when both groups received placebo , there were no differences between the groups on the MSLT , suggesting the absence of a discontinuation effect . There were no differences on daytime polysomnograms between the groups STUDY OBJECTIVES To evaluate the effects of napping , caffeine , and napping plus caffeine on performance and alertness in both laboratory and field setting s. DESIGN ( 1 ) Laboratory Study : parallel-groups design with r and om assignment to 1 of 4 experimental conditions . ( 2 ) Field Study : crossover design . SETTING Sleep laboratory and field setting s. 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 Chewing has been shown to alleviate feelings of sleepiness and improve cognitive performance during the day . This study investigated the effect of chewing on alertness and cognitive performance across one night without sleep as well as the possible mediating role of cardiac autonomic activity . Fourteen adults participated in a r and omized , counterbalanced protocol employing a chewing , placebo and caffeine condition . Participants completed tasks assessing psychomotor vigilance , tracking , grammatical reasoning , alertness and sleepiness each hour across the night . All participants received either placebo or caffeine ( 200 mg ) , while the chewing condition also chewed on a tasteless and odorless substance for 15 min each hour . Heart rate ( HR ) , root mean square of the successive differences in R-R intervals on the ECG ( RMSSD ) , and preejection period ( PEP ) were simultaneously recorded . Alertness and cognitive performance amongst the chewing condition did not differ or were in fact worse when compared with placebo . Similarly , measures of HR and RMSSD remained the same between these two conditions ; however , PEP was reduced in the later part of the night in the chewing condition compared with a relative increase for placebo . Caffeine led to improved speed and accuracy on cognitive tasks and increased alertness when compared with chewing .  Relative increases in RMSSD and reductions in HR were demonstrated following caffeine ; however , no change in PEP was seen . Strong associations between cardiac parasympathetic activity and complex cognitive tasks , as well as between subjective alertness and simpler cognitive tasks , suggest a differential process mediating complex versus simple cognitive performance during sleep deprivation 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 , r and omized , 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 objective ly 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 Abstract . The aim of this work was to investigate the potential chronobiotic properties of slow-release caffeine , in comparison with melatonin , on resynchronization of endogenous melatonin and cortisol secretions after an eastbound flight by jet incurring a time loss of 7 h. A group of 27 reservists of the US Air Force received either slow-release caffeine ( 300 mg ) , melatonin ( 5 mg ) or placebo before , during and /or after the transmeridian flight . Saliva and urine were sample d before the flight in the United States ( from day –2 to day 0 ) and after the flight in France ( from day 1 to day 10 ) . Saliva was collected once a day on waking to determine saliva melatonin and cortisol concentrations . In addition , concentrations of caffeine in saliva were determined three times a day and of 6-sulphatoxymelatonin in urine collected overnight to check that the treatment regimes had been complied with . From day 3 to day 5 , post-flight saliva melatonin concentrations were significantly different from control values in the placebo group only . During treatment with melatonin , the mean urinary 6-sulphatoxymelatonin concentration in the melatonin group was more than twice as high as in the two other groups . In the slow-release caffeine group and the melatonin group , mean saliva cortisol concentrations were significantly lower than control from day 2 to day 5 , whereas the placebo group had a mean saliva cortisol concentration significantly lower than the control value from day 2 to day 9 . In conclusion , these results indicate that administration of slow-release caffeine , as well as of melatonin , allows a faster resynchronization of hormone rhythms during the 4 days following an eastbound flight incurring the loss of 7 The effect on performance overnight of a 1 h nap taken at 0200 h was studied in six young female subjects . The subjects completed three schedules , including one with a nap and two without a nap , during which either a placebo or 300 mg caffeine was ingested at 2315 h. Performance was measured from 1700 h in the evening until 1030 h the next morning . Caffeine  improved performance overnight on almost all tasks compared with placebo . The nap had some limited beneficial effect compared with placebo , but most tasks remained impaired INTRODUCTION Interventions to maintain performance are necessary to meet dem and ing mission requirements during sustained and surge aviation operations . Tube foods are the only foods that can be consumed during a U-2 mission due to the confining and encapsulating nature of required support equipment . Caffeine is a safe and effective strategy to enhance cognitive performance and is an ingredient in some tube foods . The objective of this study was to determine whether moderate doses of caffeinated tube foods would enhance performance in a simulated U-2 mission . METHODS Volunteers were 12 healthy USAF male pilots . The study used a double blind , placebo-controlled , two-factor , repeated- measures ( five iterations per night ) design . Caffeinated ( 200 mg each ) or placebo tube food was consumed at 00:00 and 04:00 . Dependent measures assessed included st and ardized tests of cognitive performance , vigilance , and mood design ed to simulate the dem and s of a nighttime U-2 mission . RESULTS Statistically significant ( p < 0.05 ) improvements in performance due to caffeine administration compared with placebo were present in all five cognitive tasks either as main effects , interactions , or absence of significant degradation in the caffeine treatment condition compared with the placebo condition . A majority of sleep deprivation-induced performance decrements were attenuated by 200 mg of caffeine in tube food consumed every 4 h , and in some cases , performance was improved beyond baseline levels . CONCLUSIONS Caffeinated tube food maintained cognitive performance representative of U-2 long- duration mission tasks at or near baseline levels for a 9-h overnight period in qualified USAF pilots . Side effects were minor and did not differ between placebo and caffeine conditions CONTEXT In their first year of postgraduate training , interns commonly work shifts that are longer than 24 hours . Extended- duration work shifts are associated with increased risks of automobile crash , particularly during a commute from work . Interns may be at risk for other occupation-related injuries . OBJECTIVE To assess the relationship between extended work duration and rates of percutaneous injuries in a diverse population of interns in the United States . DESIGN , SETTING , AND PARTICIPANTS National prospect i ve cohort study of 2737 of the estimated 18,447 interns in US postgraduate residency programs from July 2002 through May 2003 . Each month , comprehensive Web-based surveys that asked about work schedules and the occurrence of percutaneous injuries in the previous month were sent to all participants . Case-crossover within-subjects analyses were performed . MAIN OUTCOME MEASURES Comparisons of rates of percutaneous injuries during day work  ( 6:30 am to 5:30 pm ) after working overnight ( extended work ) vs day work that was not preceded by working overnight ( nonextended work ) . We also compared injuries during the nighttime ( 11:30 pm to 7:30 am ) vs the daytime ( 7:30 am to 3:30 pm ) . RESULTS From a total of 17,003 monthly surveys , 498 percutaneous injuries were reported ( 0.029/intern-month ) . In 448 injuries , at least 1 contributing factor was reported . Lapse in concentration and fatigue were the 2 most commonly reported contributing factors ( 64 % and 31 % of injuries , respectively ) . Percutaneous injuries were more frequent during extended work compared with nonextended work ( 1.31/1000 opportunities vs 0.76/1000 opportunities , respectively ; odds ratio [ OR ] , 1.61 ; 95 % confidence interval [ CI ] , 1.46 - 1.78 ) . Extended work injuries occurred after a mean of 29.1 consecutive work hours ; nonextended work injuries occurred after a mean of 6.1 consecutive work hours . Injuries were more frequent during the nighttime than during the daytime ( 1.48/1000 opportunities vs 0.70/1000 opportunities , respectively ; OR , 2.04 ; 95 % CI , 1.98 - 2.11 ) . CONCLUSION Extended work duration and night work were associated with an increased risk of percutaneous injuries in this study population of physicians during their first year of clinical training Abstract Objectives To examine the association between self assessed driving while sleepy and the risk of serious road traffic accidents ( RTAs ) .  Design Prospect i ve cohort study . Setting France . Participants 13 299 of the 19 894 living members of the GAZEL cohort , workers and recent retirees of a French national utility company followed up since 1989 . Main outcome measures  Frequency of driving while sleepy in the previous 12 months , reported in 2001 ; rate ratios for serious RTAs in 2001 - 3 , estimated by using generalised linear Poisson regression models with time dependent covariates . Results The risk of serious RTAs increased proportionally with the frequency of self reported driving while sleepy . After adjustment for sociodemographic characteristics , driving behaviour variables , work conditions , retirement , medical conditions and treatments , depressive symptoms , and sleep disorders , the adjusted rate ratios of serious RTAs for participants who reported driving while sleepy in the previous 12 months “ a few times ” or “ once a month or more often ” were 1.5 ( 95 % confidence interval 1.2 to 2.0 ) and 2.9 ( 1.3 to 6.3 ) respectively compared with those who reported not driving while sleepy over the same period . These associations were not explained by any reported sleep disorders . Conclusions Self assessed driving while sleepy was a powerful predictor of serious RTAs , suggesting that drivers ' awareness of their sleepiness while driving is not sufficient to prevent them from having RTAs . Messages on prevention should therefore focus on convincing sleepy drivers to stop driving and sleep before resuming their journey Context The effectiveness of coffee drinking and napping to maintain alertness during nighttime driving is unknown . Contribution Twelve healthy young men drove 125 miles on a straight highway in 4 sessions : 1 session 
    Output:
    
The trials assessing the impact on errors found that caffeine significantly reduced the number of errors compared to placebo .
Based on the current evidence , there is no reason for healthy individuals who already use caffeine within recommended levels to improve their alertness to stop doing so .