Sleep Deprivation

What did early animal sleep deprivation studies find?

Prolonged sleep deprivation eventually resulted in death in dogs, rabbits, and rats.

Why were early animal SD findings hard to interpret?

Researchers could not tell whether death was caused by sleep loss itself or by the methods used to keep animals awake.

Before the 1960s, how long were most controlled human SD studies?

Less than 120 hours, or about 5 days.

What did the 205-hour sleep deprivation study find in humans?

Fatigue increased and cognitive/psychomotor functioning decreased, but no clear physiological harm was detected.

Who was Randy Gardner?

A teenager who stayed awake for an extremely long period in a non-scientific sleep deprivation experiment.

How did Randy Gardner describe the end of his experience?

He compared it to “late stage Alzheimer’s,” with major cognitive decline and emotional irritability.

What happened after Randy Gardner finally slept?

He slept a little over 14 hours and woke up groggy but not unusually so.

What are animal models of SD used for?

To study the physiological consequences of sleep deprivation in a controlled way.

What are constant and intermittent locomotion paradigms?

Methods that keep animals awake by requiring movement.

What did Rechtschaffen’s rat studies help show?

Death was an outcome of sleep deprivation itself, not just experimental conditions.

What was the purpose of the Bergmann-Rechtschaffen disk apparatus?

To minimize confounds in rodent sleep deprivation studies.

How does the Bergmann-Rechtschaffen disk apparatus work?

Two rats are placed on a rotating disk; one is sleep-deprived when EEG shows sleep onset, while the other is yoked as a control.

What is a yoked control animal?

An animal exposed to the same movement demands but not the same amount of sleep loss.

Why is the yoked control useful?

It controls for movement and fatigue, helping isolate the effects of sleep deprivation.

How long did rats survive total sleep deprivation in this model?

About 19 days.

Why should we be cautious comparing survival time across species?

Rats and humans differ greatly in survival time without food or water, so duration alone is not directly comparable.

What is more useful than survival duration in animal SD studies?

Studying the pathology and effects on tissues and body systems.

What happens to body weight during prolonged SD in rats?

Rats lose weight despite increased food intake.

Why might SD cause weight loss?

Increased energy demands from immune abnormalities, oxidative stress, and cell injury.

What happens to infection resistance during prolonged SD?

Resistance decreases, and bacteria may appear in normally sterile organs.

What endocrine changes occur with SD?

Anabolic hormones such as thyroid-stimulating hormone, insulin, and growth hormone are suppressed.

What is the overall conclusion from animal SD models?

Sleep deprivation has slow, widespread, insidious effects on both brain and body systems.

Why must human sleep have enough duration and continuity?

To support waking alertness, attention, cognitive performance, and health.

What is habitual short sleep associated with?

Sleepiness, accidents, cognitive deficits, obesity, diabetes, hypertension, and all-cause mortality risk.

What percentage of U.S. adults chronically sleep less than 7 hours on weekdays?

About 35–40%.

Why is chronic partial sleep deprivation important?

It is common and its effects cannot simply be predicted from acute total sleep deprivation studies.

What medical conditions can disrupt sleep or cause SD?

GERD, renal disease, infectious disease, cancer, fibromyalgia, chronic pain, and chronic fatigue.

What substances or drugs can affect sleep?

Antihistamines, cardiovascular medications, nicotine, alcohol, and caffeine.

What does MSLT stand for?

Multiple Sleep Latency Test.

What does the MSLT measure?

How quickly someone falls asleep during scheduled daytime naps.

How many nap trials are in the MSLT?

Five scheduled naps.

How far apart are MSLT nap trials?

Each begins 2 hours after the start of the previous nap trial.

What happens during an MSLT nap trial?

The person lies quietly and tries to sleep while sleep latency is measured.

When does an MSLT nap trial end if the person falls asleep?

They are awakened 15 minutes after falling asleep.

When does an MSLT nap trial end if the person does not fall asleep?

The trial ends after 20 minutes.

What is chronic sleep restriction?

Repeatedly getting less sleep than needed over many days or weeks.

Why can chronic sleep restriction be dangerous?

People may underestimate their impairment while alertness and safety decline.

What are the three main categories of human SD experiments?

Total sleep deprivation, sleep restriction, and sleep fragmentation.

What is total sleep deprivation?

Staying awake for an entire sleep period or longer.

What is sleep restriction?

Limiting sleep time, often over several nights.

Why do sleep restriction studies have ecological validity?

They resemble real life more than staying awake all night.

What is sleep fragmentation?

Repeated disruption of sleep continuity, even if total sleep time is not greatly reduced.

What is one major cognitive effect of SD?

Psychomotor impairment.

How can SD-related psychomotor impairment compare to alcohol?

It can be equivalent to impairment from alcohol above the legal limit.

What is a lapse of sustained attention?

A brief failure to respond or stay alert during a task.

What cognitive changes are most reliable after SD?

Attention lapses, response disinhibition, and impaired sleep-dependent memory consolidation.

Why is measuring cognitive effects of SD difficult?

SD increases variability within and between people.

What is state instability?

Fluctuation in performance within the same person during sleep deprivation.

What is differential vulnerability?

Some people are more impaired by sleep loss than others.

What does PVT stand for?

Psychomotor Vigilance Task.

What does the PVT measure?

Behavioral alertness and sustained attention.

Why is the PVT useful in SD research?

It is sensitive to sleep loss and not strongly affected by aptitude or learning.

What real-life abilities does the PVT relate to?

Vigilant attention needed for learning, driving, and safety.

What happens to PVT performance during sleep restriction?

Lapses increase over days as sleep debt accumulates.

What does “dose-response” mean in sleep restriction studies?

Less sleep leads to greater impairment.

What is TIB?

Time in bed.

What did 4-hour and 6-hour TIB studies show?

Performance worsened over time, especially with less sleep.

What happens to performance during extended total SD?

It gets worse as sleep debt builds, with fluctuations across the circadian cycle.

When are SD performance lapses often worst?

During the early morning hours.

Can performance recover after total sleep deprivation?

Recovery can be fairly rapid after sleep, especially compared with chronic restriction.

What is sleep extension?

Increasing sleep time before a period of sleep restriction.

What effect did prior sleep extension have before sleep restriction?

It reduced the buildup of performance deficits and sped recovery.

What did the medical student study compare?

Sleep and cognitive function during vacation versus school.

What happened to medical students during school periods?

They slept less and showed worse attention/executive functioning measures.

What did the surgeon sleep-loss study test?

Microsurgical performance after normal sleep versus sleep restriction.

Who participated in the surgeon study?

Junior surgery fellows and senior surgeons.

How much sleep opportunity was used in the restricted condition?

3 hours time in bed.

What happened to junior surgeons after sleep restriction?

Their performance worsened; they took longer and had more tremors.

What happened to senior surgeons after sleep restriction?

Their dexterity appeared unchanged in the reported conclusion.

Why should the senior surgeon conclusion be questioned?

Small samples and individual differences may hide important effects.

What is AHI?

Apnea-Hypopnea Index.

What does AHI measure?

Severity of breathing disruptions during sleep, often used as a marker of OSA.

What happened to surgeons with high AHI after sleep deprivation?

They took 26% longer to complete surgery compared with baseline.

What are individual differences in vulnerability to sleep loss?

People vary greatly in how impaired they become after the same amount of sleep loss.

Are vulnerability differences explained by demographics, IQ, or sleep need?

No, not fully.

Is vulnerability to SD thought to have genetic influences?

Yes, it may be a polygenic trait.

What is familial natural short sleep?

A genetic trait where people naturally sleep only 4–6 hours and still feel well rested.

How are familial natural short sleepers different from chronically sleep-restricted people?

They feel rested and may not show the same health risks linked to sleep restriction.

What did NPSR1 mutation studies in mice find?

Mutant mice had more mobility time and shorter sleep duration.

How did NPSR1 mutant mice respond to SD?

They were more resistant to cognitive impairment induced by sleep deprivation.

What social behavior did later SD studies examine?

Helping behavior and altruism.

What did Experiment 1 on helping behavior test?

Participants completed helping measures after sleep and after one night of SD.

What did Experiment 1 find?

Sleep deprivation reduced willingness to help others.

What happened to the social cognition network after SD?

Functional connectivity was reduced.

What did Experiment 2 on helping behavior examine?

Sleep diaries and helping questionnaires across 4 days in daily life.

What did Experiment 2 find?

Worse sleep efficiency predicted lower desire to help the next day.

What did Experiment 3 use as a societal measure of helping?

More than 3 million charitable donations.

What real-world sleep loss did Experiment 3 examine?

The 1-hour sleep opportunity loss after spring daylight saving time.

Why is sleep difficult in outer space?

Light, noise, temperature, microgravity, and unusual environments interfere with sleep.

What sleep problem did Neil Armstrong reportedly have on the moon?

He was unable to sleep all night.

How much did Buzz Aldrin reportedly sleep on the moon?

Only a couple of hours of drowsing.

What has NASA done to improve astronaut sleep?

Developed light- and sound-attenuated sleep stations on the ISS.

Are sleep problems still common in astronauts?

Yes, sleep deprivation and fatigue remain common complaints.

How much protected sleep time does NASA mandate?

8.5 hours per night.

What is common during spaceflight despite sleep protections?

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