Stable interindividual differences in modafinil's effect on vigilance during sleep deprivation.

Area of Science:

• Pharmacology and Toxicology
• Human Factors and Aviation Psychology
• Sleep Medicine and Circadian Rhythms

Background:

• The off-label use of modafinil in military aviation is regulated, but safety concerns persist.
• Understanding individual differences in modafinil's effects is crucial for operational safety.
• Modafinil is used to counteract fatigue in demanding operational contexts.

Purpose of the Study:

• To investigate the stability of interindividual differences in modafinil's benefits and risks.
• To assess modafinil's impact on vigilance and sleepiness in military student pilots under extended wakefulness.
• To examine the relationship between cognitive performance and self-monitoring abilities.

Main Methods:

• A within-subject crossover design compared modafinil (400 mg) versus placebo in 11 healthy military student pilots.
• Participants underwent 24 hours of sustained wakefulness with repeated assessments of vital signs, mood, and vigilance (Psychomotor Vigilance Task - PVT).
• Genotyping for COMT and PER3 polymorphisms was performed on a subset of participants.

Main Results:

• Modafinil significantly improved PVT performance and reduced subjective sleepiness during sleep deprivation (2 AM and 4 AM).
• High stability (ICC = 0.90) was observed in interindividual differences in reaction time improvements.
• Reaction time performance correlated with self-monitoring scores only in the placebo condition.

Conclusions:

• Stable interindividual differences exist in modafinil's effectiveness against sleep deprivation-induced vigilance decrements.
• Further research is needed to quantify modafinil-induced overconfidence and rebound sleepiness in operational settings.
• Findings suggest consistent individual responses to modafinil, impacting risk-benefit assessments in military aviation.