Sleep and Executive Performance: The Hidden Impairment

The Van Dongen Study

Hans Van Dongen, Greg Maislin, Janet Mullington, and David Dinges published "The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology from Chronic Sleep Restriction and Total Sleep Deprivation" in SLEEP in 2003 (Vol. 26, No. 2, pp. 117–126).

The study randomized participants to spend either 4 hours, 6 hours, or 8 hours in bed per night for 14 consecutive days. A separate group underwent total sleep deprivation. Cognitive performance was measured multiple times daily using the psychomotor vigilance task (reaction time) and digit symbol substitution (a measure of processing speed and attention).

Performance in the 4-hour and 6-hour groups declined progressively across the 14 days with no stabilization. The impairment continued to accumulate across the entire study period. There was no adaptation or tolerance to the sleep restriction. The 8-hour group showed no significant performance decline across the same period.

The Underestimation Problem

The most consequential finding in the Van Dongen study is not the performance impairment itself. It is the divergence between objective impairment and subjective awareness of it.

Participants rated their sleepiness daily using the Karolinska Sleepiness Scale. The 4-hour and 6-hour groups showed only modest increases in subjective sleepiness ratings across the 14 days. Critically, participants in these groups reported similar levels of sleepiness to each other. They did not subjectively differentiate their conditions despite the 4-hour group showing substantially worse objective performance. And neither restriction group reported the level of subjective sleepiness that matched their objective cognitive impairment.

The practical interpretation: people who chronically sleep 6 hours per night feel somewhat tired but functional. They are not experiencing the dramatic subjective impairment that would signal a problem to them. Their felt competence is relatively intact; their actual performance on attention-demanding, time-sensitive tasks is severely compromised. The person who is most impaired by their sleep pattern is the least positioned to self-diagnose it.

Executive Function and High-Stakes Decisions

The cognitive functions most impaired by sleep restriction are precisely those most required for senior leadership: sustained attention, working memory, emotional regulation, and judgment under uncertainty. The psychomotor vigilance task captures sustained attention, which is the ability to maintain performance on a demanding task over time. Sleep-restricted participants show increasing lapses (failures to respond within the allowed window) that accumulate across the study period.

• Risk assessment and negotiation. Sleep-restricted individuals show reduced sensitivity to social cues, increased risk tolerance, and less accurate probabilistic reasoning. These are the functions most needed in high-stakes negotiations, investment decisions, and crisis responses, exactly the contexts in which senior leaders who sleep less tend to be most active.
• Emotional regulation. Amygdala reactivity to threatening stimuli increases with sleep restriction, while prefrontal regulatory capacity decreases. The result: sleep-restricted executives tend to over-react to negative information and under-regulate conflict responses, a pattern that produces worse decisions precisely in the emotionally loaded situations that most require good judgment.
• Meetings and scheduling. The timing of high-stakes meetings matters because cognitive performance tracks circadian rhythms and sleep pressure. Scheduling the most demanding cognitive work (complex decisions, adversarial negotiations, sensitive personnel matters) at times when sleep-restricted cognitive performance is at its nadir compounds the impairment. The executive who sleeps 6 hours and schedules their hardest work at the end of the day is stacking two performance penalties.