Modafinil and caffeine improve vigilance of individuals deprived of sleep, study finds

A study on members of the Royal Netherlands Air Force found that 200 mg of modafinil and 300 mg of caffeine effectively counter the adverse effects of being awake for 17 hours on vigilance. The effect of modafinil seems to be longer-lasting than the effect of caffeine. The study was published in the Journal of Psychopharmacology.

Being able to stay awake and fully vigilant is of utmost importance for aviators. While drivers of ground vehicles can relatively easily stop and rest when they feel tired, this is not the case with pilots. For example, a voice recorder extracted in 2010 from a crashed Air India Express passenger flight recorded sounds of snoring just before the crash. The investigation concluded that the captain of the plane was asleep for more than 90 minutes of the 2-hour flight. It ascribed this development to his lack of sleep on the previous day.

The best way for aviators to stay vigilant is if they perform their duties only when they are well-rested. However, that is sometimes not possible. For this reason, research into chemical substances that could help these individuals remain vigilant is of substantial scientific importance. Two such possible substances are caffeine and modafinil.

Modafinil is a medication primarily used to promote wakefulness and alertness in individuals with sleep disorders like narcolepsy, sleep apnea, and shift work sleep disorder. It is a synthetic drug that was originally developed in France in the late 1970s and early 1980s. Modafinil is a prescription medication found on the market under different brand names including Provigil and Alertec.

Caffeine is a natural stimulant found in coffee and cacao beans, certain nuts and a number of other plants. It is a popular ingredient in beverages like coffee, tea, energy drinks, and soft drinks, as well as in some over-the-counter medications used to treat headaches and drowsiness.

Study author Yara Q. Wingelaar-Jagt and her colleagues wanted to determine the effects of a single dose of modafinil (200 milligrams) on vigilance during a limited period of sleep deprivation compared to the effects of placebo and a single dose of caffeine (300 milligrams). They expected that both caffeine and modafinil will successfully counteract the adverse effects of fatigue on vigilance (compared to placebo), but that the effects of caffeine will kick-in earlier. They conducted an experiment.

Participants were 32 healthy members of the Royal Netherlands Air force aged between 18 and 60 years who volunteered for participation. 5 of the participants were females and 21 of them were pilots. The study was conducted on 3 different days, one for each treatment. There were at least 7 days between test days.

On a test day, participants woke up as usual. They were free to drink caffeine drinks till 5:00 PM, the same as usual. At 6:00 PM, they started familiarizing themselves with vigilance testing equipment. At midnight, participants completed baseline testing. An hour later (1:00 AM) they took the medications. Depending on the testing condition, it was either a capsule containing 200 mg of modafinil, a capsule containing 300 mg of caffeine or an identically looking capsule without active components.

Neither the study participants nor the researchers working directly with them knew which capsule they were taking. It was a double-blind study. After taking the capsule, study participants completed assessments and tests once every hour till 4:00 AM, and after that at 6:00 AM and at 8:00 AM.  The order of study treatments (i.e. which capsule they take on which day) was randomized for each participant to counter any possible effect of the order of treatments.

During the night, participants completed two vigilance tests – the Vigilance and Tracking test (VigTrack) and the Psychomotor Vigilance task (PVT). They also completed an assessment of sleepiness (the Stanford Sleepiness Scale). Researchers took participants’ blood samples at 4 occasions during the night. They also reported on their belief about which medication was given to them. Participants were correct in guessing the substance they received 57% of the time.

Results showed that participants had much faster reaction times on the Vigilance and Tracking test when they were on modafinil and caffeine compared to when they received placebo. The results also depended on the time of the assessment. The highest difference between performance while under the effects of modafinil and caffeine compared to placebo were between 4:00 and 8:00 AM. Participants on modafinil made fewer mistakes on this test compared to when they received placebo.

The psychomotor test results also showed better performance when participants consume modafinil or caffeine compared to placebo. Their reaction times were faster and this effect started some 2 hours after taking the capsules. Additionally, performance was less impaired in early morning hours (6:00-8:00 AM) when participants took modafinil compared to what they were when participants took caffeine.

“The present study demonstrates that 200mg modafinil and 300mg caffeine significantly improve vigilance compared with placebo during an extended period of continuous wakefulness (mean 17.3 h), including the WOCL [the Window of Circadian Low, the period of the daily cycle when fatigue and sleepiness are greatest and people are least able to perform mental or physical work], without causing side effects. The most notable effects occurred in the early morning (between 4:00 and 6:00AM), although Psychomotor Vigilance Task parameters improved as early as 2 h after administration,” the study authors conclude.

The study sheds light on the effects of modafinil on vigilance after a night without sleep. However, it also has limitations that need to be taken into account. Notably, the study sample was very small and the majority of participants were military pilots i.e., individuals in excellent psychophysical condition. Results on a group more representative of the general population might not be the same.

The study, “Effects of modafinil and caffeine on night-time vigilance of air force crewmembers: A randomized controlled trial”, was authored by Yara Q. Wingelaar-Jagt, Charelle Bottenheft, Wim J. Riedel, and Johannes G. Ramaekers.


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