Comparison of effects of modafinil and caffeine on fatigue-vulnerable and fatigue-resistant aircrew after a limited period of sleep deprivation
What this study found
Both modafinil and caffeine improved fatigue-related performance versus placebo during sleep deprivation. For both active treatments, the strongest effects were seen for Psychomotor Vigilance Task outcomes, with significant main effects of treatment for mean reaction time (F(2,9)=11.448, p<0.001) and number of lapses (F(2,9)=24.101, p<0.001). Pairwise comparisons favored modafinil versus placebo for PVT mean reaction time (p<0.001) and lapses (p=0.036), and favored caffeine versus placebo for PVT mean reaction time (p<0.001) and lapses (p<0.001). Subjective sleepiness and Vigil Track…
- Study & population
- Healthy adult aircrew from the Royal Netherlands Air Force completed a controlled sleep-deprivation protocol in a comparative intervention study.
- Intervention
- Modafinil was given as 200 mg capsules once immediately after midnight on each trial day.
- Key limitation
- The active-arm sample sizes were modest, and the sleep-deprivation exposure was limited, which restricts precision and longer-term inference.
View source
Open PDFOriginal abstract
Introduction: Literature suggests pilots experience fatigue differently. So-called fatigue-resistant or -vulnerable individuals might also respond differently to countermeasures or stimulants. This study, which is part of a larger randomized controlled clinical trial, aims to investigate the effect of caffeine and modafinil on fatigue-resistant and -vulnerable pilots. Methods: This study included 32 healthy employees of the Royal Netherlands Air Force, who completed three test days, separated by at least 7 days. After a regular work day, the subjects were randomly administered either 300 mg caffeine, 200 mg modafinil or placebo at midnight. Hereafter the subjects performed the psychomotor vigilance test (PVT), vigilance and tracking test (VigTrack) and Stanford sleepiness scale (SSS) six times until 8 a.m. the next day. Subjects were ranked on the average number of lapses on the PVT during the placebo night and divided into three groups: fatigue-vulnerable (FVUL), -intermediate (FINT) and -resistant (FRES), with 11, 10 and 11 subjects in each group, respectively. Area under the curve (AUC) of the PVT, VigTrack and SSS during the test nights were calculated, which were used in univariate factorial analysis of variance (ANOVA). Tukey’s HSD post hoc tests were used to differentiate between the groups. Results: A significant effect of treatment was found in the ANOVA of both PVT parameters, VigTrack mean reaction time and SSS. There was a statistically significant effect of fatigue group on all PVT parameters and VigTrack mean percentage omissions, where FINT and FRES scored better than FVUL. There was a significant interaction effect between treatment and fatigue group for PVT number of lapses. This is congruent for the AUC analyses in which for all parameters (except for the SSS) the performance of the FVUL group was consistently worse than that of the FINT and FRES groups. Discussion: This study demonstrates that the performance of individuals with different fatigue tolerances are differently affected by simulants after a limited period of sleep deprivation. The classification of fatigue tolerance through PVT lapses when sleep deprived seems to be able to predict this.