Modafinil improves alertness, vigilance, and executive function during simulated night shifts.

STUDY OBJECTIVES: To assess the effect of 200 mg of modafinil compared to placebo on alertness, neurobehavioral performance, and executive function during 4 consecutive simulated night shifts.

DESIGN: Double-blind, randomized, parallel groups.

SETTING: Sleep research facility.

PARTICIPANTS: 32 male and female volunteers between the ages of 18 and 55 years.

INTERVENTIONS: 200 mg of modafinil or placebo given nightly on the 4 consecutive simulated night shifts.

MEASUREMENTS AND RESULTS: Subjects were randomly assigned to 1 of the 2 treatment conditions, following medical, psychiatric, and polysomnographic screening. On 4 consecutive nights, subjects took study drug at 2200, and then from about 2300 to 0730 participated in a simulated night shift that included the Maintenance of Wakefulness Test, Psychomotor Vigilance Test, Digit Symbol Substitution Test, measures of subjective alertness, and multiple executive-function measures. At 0800, daytime sleep periods were recorded polysomnographically for 6 to 8 hours. Alertness--as measured by the MWT, vigilance and reaction time as indexed by Psychomotor Vigilance Test lapses, and slowest 10% of reaction times--and 3 executive-function tasks showed significant enhancement with modafinil versus placebo. Subjective sleepiness at night and some performance measures did not show consistent treatment differences. Daytime sleep showed minimal differences between conditions.

CONCLUSIONS: The physiologic sleepiness and neurobehavioral deficits that occurred during the hours of a typical night shift were clearly attenuated by modafinil. Modafinil also had beneficial effects on some measures of executive function.