Caffeine improves reaction time, vigilance and logical reasoning during extended periods with restricted opportunities for sleep.

Gary H Kamimori,Charmaine M Tate,Phil Niro,David M Voss,Harris R Lieberman,Tom M Mclellan

doi:10.1007/s00213-014-3834-5

Abstract

RationaleVarious occupational groups are required to maintain optimal physical and cognitive function during overnight periods of wakefulness, often with less than optimal sleep. Strategies are required to help mitigate the impairments in cognitive function to help sustain workplace safety and productivity.ObjectivesTo test the effectiveness of repeated 200 mg doses of caffeine on cognitive function and live-fire marksmanship with soldiers during three successive nights of sustained wakefulness followed by 4-h afternoon sleep periods.MethodsTwenty Special Forces personnel (28.6 ± 4.7 years, 177.6 ± 7.5 cm and 81.2 ± 8.0 kg) were randomly assigned to receive four 200-mg doses of caffeine (n = 10) or placebo (n = 10) during the late evening and early morning hours during three successive days. An afternoon 4-h sleep period followed. The psychomotor (PVT) and field (FVT) vigilance, logical reasoning (LRT) tests and a vigilance monitor assessed cognitive function throughout the study. Live-fire marksmanship requiring friend–foe discrimination was assessed.ResultsCaffeine maintained speed on the PVT (p < 0.02), improved detection of events during FVT (p < 0.001), increased number of correct responses to stimuli as assessed by the vigilance monitor (p < 0.001) and increased response speed during the LRT (p < 0.001) throughout the three overnight testing periods. Live-fire marksmanship was not altered by caffeine.ConclusionsA total daily dose of 800 mg caffeine during successive overnight periods of wakefulness is an effective strategy to maintain cognitive function when optimal sleep periods during the day are not available.

Highlights

Many occupational groups, such as shift workers, long-haul truck drivers, emergency responders and deployed military personnel, must maintain optimal cognitive and physical performance over several consecutive days; often, this occurs with inadequate sleep opportunities provided at non-optimal periods during the day
Strategies to counter the impairments in cognitive function that accompany sleep loss (Belenky et al 2003; Lieberman et al 2002, 2005; Thomas et al 2000) are needed to help sustain workplace safety and productivity
A relatively high 600-mg dose of caffeine is as effective as prescription medications such as modafinil and amphetamines for improving cognitive function and countering sleep loss during periods of prolonged wakefulness (Wesensten et al 2002, 2004, 2005a)

Summary

Introduction

Many occupational groups, such as shift workers, long-haul truck drivers, emergency responders and deployed military personnel, must maintain optimal cognitive and physical performance over several consecutive days; often, this occurs with inadequate sleep opportunities provided at non-optimal periods during the day. Under these conditions, strategies to counter the impairments in cognitive function that accompany sleep loss (Belenky et al 2003; Lieberman et al 2002, 2005; Thomas et al 2000) are needed to help sustain workplace safety and productivity. Caffeine is a viable candidate to sustain productivity and safety in the workplace during periods of extended operations that restrict sleep

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Discussion

Conclusion