**3.1 Fatigue:**

Definition of sleep

Physiology of sleep

Sleep disorders

Circadian rhythm and circadian desynchronosis (including jet lag)

Definition of fatigue

Causes of fatigue

Predisposing and contributing factors (individual, environmental,
operational)

Symptoms, signs, and performance effects of fatigue

Prevention and countermeasures

**[INSTRUCTION]{.underline}**

"I departed from a parallel taxiway instead of the runway. I never
thought I could ever do such a stupid, unsafe maneuver. Leading factor:
fatigue; Second: "That will never happen to me" attitude; Third:
complacency; Fourth: weather; Fifth: I was in a hurry to get home. We
had already been up more than 24 hours even though, technically, we were
legal ... This event has cautioned me about two things: 1) fatigue is
insidious, and 2) I'm not as good as I thought I was, but I'll get
better-for sure."

\-\--Anonymous corporate pilot, quotation in *Callback*, NASA's Aviation
Safety Reporting System bulletin, Number 277, October 2002.

**[INTRODUCTION]{.underline}**

Since World War II, flight operations have been increasingly performed
over longer distances, longer intervals, and across multiple time zones.
The biology governing the performance of men and women has not changed,
however. The timing, quality and quantity of sleep needed may vary among
individuals, but among all people, unalterable physiological needs and
constraints exist. Efforts are being made within aerospace to design and
employ behavioral and pharmacological interventions to overcome the
effects of fatigue and sleepiness in personnel required to operate in a
sleep deprived condition and at times when they would normally be
sleeping.

Complicating matters, however, is that ultra long haul aircraft that can
fly 20 hours non-stop are in development, necessitating the need for
more augmented or dual crews with appropriate sleeping compartments. The
development and implementation of automated flight systems may result in
new opportunities for crew resource management (CRM), allowing for fewer
pilots to be in the cockpit and more time for alternate pilots to get
adequate sleep. Unfortunately, the more automated systems may also
promote complacency and inattention because there is not enough to keep
the operators engaged with the aircraft.

Aviation accidents are caused by human error 80% of the time. The role
of fatigue and circadian rhythm disorders (desynchronoses) in these
mishaps is probably underestimated. The accident rate for long haul
commercial flights is higher than for short and medium haul flights,
leading to speculation that fatigue and sleepiness plays a more
significant role with the larger transmeridian changes. It has been
estimated that 15-20% of all transportation accidents are related to
fatigue, which surpasses that of alcohol and drugs^1^.

Recognition of the causes and signs of fatigue is central to safe and
effective air operations. Every flight operation has its own tempo, time
required to perform the major tasks, personnel structure, and number of
personnel. There are a number of different aerospace scenarios, ranging
from ferrying operations to air rescue, combat and space flight.
Prevailing cultural attitudes may pose a hindrance to adequate resting
and napping. Our society now sleeps about an hour or two less on average
than our ancestors a century ago. Sleep and the demand for productivity
are at odds, and adult napping is virtually frowned upon.

The sleep culture of modern society has fundamentally changed and as a
result, fatigue-related problems have reached significant proportions in
the population. Technological changes have led to sleep requirements
being pushed down on the needs scale. One-third of adults in a recent
survey reported significant daytime sleepiness on the Epworth Sleepiness
Scale, and 6% indicated they were severely sleepy^2^. Forty percent of
adults indicated they were so sleepy during the day that it interfered
with their daily activities, and 18% said they suffered from this type
of problem several days a week. More than half the people surveyed also
reported that chronic sleepiness adversely affected their mood, energy
levels, concentration ability, and overall health, as well as their
ability to pursue personal interests and maintain quality relationships
with their family and friends. Obviously, daytime sleepiness exerts a
negative impact on mental and physical well-being and general
productivity. A

National Sleep Foundation
([www.sleepfoundation.org](http://www.sleepfoundation.org/)) sponsored
survey found that the U.S. workforce complains that on-the-job
concentration, problem-solving, interpersonal relationships, and
performance suffer because of fatigue. Both personal and on-the-job
safety is adversely affected by sleepiness. Improperly managed pilot and
air traffic controller fatigue can become a significant problem in
flight environments that require alertness, complex judgment, and quick
reactions. Fatigue touches every aspect of life in modern society,
including aviation sectors in which requirements for unpredictable and
extended work episodes often occur at times when alertness tends to be
most compromised.

**[CAUSES AND EFFECTS OF SLEEP DEPRIVATION AND
DESYNCHRONOSES]{.underline}**

**The Role of the Body Clock:**

The internal circadian clock, located in the suprachiasmatic nucleus of
the hypothalamus, is one of two principal physiological determinants of
waking alertness and performance^4^. The circadian clock controls the
24-hour rhythm for a wide range of functions, including performance,
alertness, behavior, and mood. One prominent circadian pattern is
exhibited by the sleep/wake cycle, with biological programming for a
consolidated period of daytime wakefulness and nighttime sleep,
recurring in a regular 24-hour pattern. Alertness and the ability to
perform are related to two basic neurophysiological forces: the body\'s
circadian pacemaker (or biologic clock) and the drive or need for sleep
(based on the length of previous wakefulness). Sleepiness cycles over a
24-hour period, and during this period, humans are programmed for two
separate time frames of physiological sleepiness and two windows of
alertness. For most, maximal sleepiness occurs at the lowest point of
the circadian cycle, typically from about 3 to 5 AM, when the lowest
levels in many functions are observed, such as temperature, mood, and
performance. A second interval of sleepiness occurs at about 3 to 5 PM.
The two windows of intrinsic alertness occur at approximately 9 to 11 AM
and 9 to 11 PM.

Several factors affect the specific timing of these episodes of
alertness and sleepiness and the degree of change observed during these
times. The ability to adapt to a new time zone or shiftwork pattern
takes up to 3 weeks, depending on individual differences, the frequency
and magnitude of the time shifts. Environmental (light, activity) and
social factors (sleep habits, social interactions, work schedule) may
either assist or prevent the accommodation to a new schedule. Constantly
changing shifts are more disruptive because people rarely remain on the
schedule long enough to adjust.

Abruptly changing to a new schedule or time zone can result in both
internal and external desynchronization. External desynchronization
involves the internal clock being out of synch with external time cues.
Internal desynchronization involves the internal rhythms (e.g.,
temperature, sleep/wake, hormone secretion) being out of synch with one
another. It can take from a few days to weeks for full circadian
resynchronization. The adjustment time needed is dependent on factors
such as direction flown, number of time zones crossed, and light
exposure.

Light is perhaps the most powerful cue that sets the circadian clock.
Light exposure at times of clock sensitivity can be used to alter the
clock and reset it to a new time zone or shift schedule. It can take 48
to 72 hours with expert application of light/dark cues to readjust the
internal circadian clock. Therefore, there will not be significant
circadian adjustment during trips of less than approximately 3 days; no
matter what adaptation strategies are used.

**The Role of Acute and Chronic Sleep Loss:**

Human capability and performance can be reduced with sleep loss^5^.
Studies have shown that decision-making, reaction time, memory,
communication skills, mood, vigilance, alertness, and more can be
degraded by sleep loss and circadian disruption. Operationally, it is
important to note that these reductions may not occur as a smooth
function. Performance becomes more variable when humans fatigue, and the
onset of significant performance decrements can occur quickly. While
performance may be at an acceptable and consistent level at one point,
only moments later it can become irregular and significantly eroded.
Falling asleep represents the absolute performance failure. However,
performance can be reduced and can represent a safety risk well before
or in the absence of an unplanned sleep episode.

Sleepiness and fatigue cause reduced ability to function. Chronic sleep
restriction to fewer than 6 hours per night has been shown to impair
performance and increase the tendency to involuntarily fall asleep
during normal wakefulness. Besides the chronic sleep deprivation, it is
without doubt that many transportation workers are at serious risk for
sleepiness while operating because of circadian disruptions from
rotating between day and night duty periods.

Schedule rotation is a problem for aviation personnel as well. Studies
have shown that irregular work schedules, compared with consistent
daytime work schedules, are associated with an increase in vehicle
accidents, more frequent complaints about inadequate daily sleep, a
greater reliance on caffeine to boost performance, and an increase in
the probability that alcohol will be used as a sleep aid.

Lapses (the failure to respond to a situation) increase with increasing
levels of fatigue. Lapses may be associated with microsleeps (episodes
of sleep lasting 0.5 to 10 seconds), but can also occur without sleep
onset. The four sleep-related factors involved in fatigue-induced
performance impairments are the circadian phase of the biological clock,
the presence of acute sleep loss, the presence of cumulative sleep loss
and the presence of sleep inertia. Lapses increase 2 to 10 times during
night operations without pre-existing sleep loss. Acute sleep loss
(following a single night of sleep loss) results in 4 to 10 times more
lapses, while chronic sleep deprivation by reducing sleep 2-3 hours per
night for 1 week may increase lapses by 3 to 5 times normal.

Sleep inertia is the difficulty awakening from a sleep episode. Sleep
inertia results in increased lapses and is most likely to be present
after abrupt awakenings and awakening from stages 3 and 4 NREM sleep.
The potential for catastrophe due to lapses is enormous. An aircraft
going 250 kits on a glide path, for example, can travel over 400 feet
during a 1-second lapse. Microsleeps have been shown to occur in aircrew
during landing approaches in commercial carriers.

The degree of resulting fatigue and risk of mishaps are dependent on the
type of aircraft, mission, operations schedule, and environmental
conditions. Increased workload, noise, temperature extremes and
turbulence tend to exacerbate the effects of sleep loss and jet lag.
Reaction times may be markedly slowed, which can be critical when rapid
reactions are necessary. False responding also increases, i.e. the pilot
may take action when no action is warranted, especially when aware of
having missed signals. The resulting anticipation of another event and
over attention on individual signals or problems further reduces
situational awareness. Fatigue increases calculation errors, logical
errors and ineffective problem solving. The member is less able to think
of new solutions and repeatedly tries the same approach to a situational
problem.

Memory deficits progressively worsen with fatigue and sleep loss. The
sleepy and tired crewmember reads or hears instructions repeatedly but
cannot retain the information, leading to critical errors and
uncertainty about the status of the situation. Performance variability
results from increased lapses and errors of omission. Although the
member often becomes aware of the shortcomings in performance and
responds by trying to increase self-motivation and effort, performance
improvement is short-lived. He/she may perceive the operation as more
stressful and tiring as the effort continues. Ultimately, the
crewmember's motivation to perform well and avoid risks erodes.

No individual is immune to the effects of sleep loss and fatigue,
although there are individual differences in the ability to tolerate
sleep loss. After one night of sleep loss, half of healthy individuals
perform reasonably well, but the remainder exhibit moderate to severe
performance deficits. After 36 hours, there is little difference between
individuals in their ability to perform\-\--all have severe performance
deficits.

The ability of a fatigued crewmember to self assess alertness is also
limited^6^. In fatigued individuals, initial good performance early on
may give a false sense of security. As time goes by, performance
deteriorates. A crewmember is also more likely to overestimate his or
her ability to perform if asked whether he or she is tired or able to
perform. Relief from other crewmembers when signs of fatigue are
observed (eyelids drooping, yawning, irritability, forgetfulness) is
crucial.

Although fatigue once was thought to be a minor concern that could be
overcome with sufficient motivation, training, or experience, it is now
clear that the basis for this problem extends far beyond psychological
factors.

Sleep is a physiological need similar to hunger and thirst and adequate
undisturbed sleep is the only remedy for sleepiness. When aircrews try
to ignore the sleepiness, they become even sleepier and must expend
greater and greater amounts of energy to stay awake and complete tasks.
Fatigue from long work hours, sleep deprivation, and circadian
disruption has been recognized as a substantial cause of serious human
errors, and most recently, the effects of fatigue have received
heightened consideration in the aviation sector.

Research Studies in Real Aviation Settings

The NASA Fatigue/Jetlag Program was initiated in 1980 in response to a
Congressional inquiry about whether fatigue was a safety issue in flight
operations. In 1990, the program evolved into the NASA Fatigue

Countermeasures Program to emphasize strategies that would address the
issue. Each branch of the Department of Defense and the FAA has also
studied fatigue and its effects on safety and mission readiness.

The NASA Program used a broad range of research methodologies and
measures. Research projects included studies in controlled laboratory
situations, high-fidelity full-motion simulators, and field studies
during actual flight operations^7^. The range of measures included
subjective surveys and diaries, physiological measures of brain activity
and core body temperature, and performance variables. A number of other
scientists and groups have also conducted similar research.

To fully appreciate the impact of fatigue on overall safety, it is
necessary to understand that many of our current scheduling and crew
rest practices may be unintentionally contributing to degraded
alertness. While societal demand and technology have evolved
significantly, human physiology has remained unchanged. As humans, we
have intrinsic physiological requirements for sleep and a stable
internal biological clock. If sleep is lost or there is disruption of
the internal clock, there are significant decrements on waking
performance, alertness, and safety.

Humans were not designed to operate 24/7, which challenges the direction
of modern society*.* The scientific data are clear that there are risks
associated with presuming that human operators can function
round-the-clock with the same efficiency, safety, and consistency now
expected of our technology. Just as the machines have certain
capabilities and operating limitations, so do the humans who design,
implement, and operate them. The following are a few examples of data
obtained from real air operations.

A NASA field study was conducted with 74 commercial pilots from two
different airlines flying short-haul (flight legs less than 8 hrs)
operations^8^. A sleep/wake diary was completed for three days before
the trip, throughout the trip, and for three days after returning.

Core body temperature was monitored to examine circadian variables, and
wake/rest activity patterns were assessed with a wrist worn movement
device (autograph). A researcher accompanied the crews on the flight
deck during the trips. Overall, the trips averaged 10.6 duty hours and
involved 4.5 hours of flight time and 5.5 flight legs per trip day.
About one-third of the duty periods were longer than 12 hours, and the
average rest period (i.e., off-duty) was 12 hours long. The logbook data
revealed that during the trip schedule, pilots reported that they slept
less; awoke earlier; had more difficulty falling asleep; had lighter,
less restful sleep; and poorer overall sleep quality. Overall, 67% of
crewmembers had at least one hour less sleep per 24 hours during the
trip (compared to pre-trip amounts), and 30% averaged two hours of sleep
loss. Pilots reported consuming increased amounts of caffeine, snacks,
and alcohol during the trip schedule. They also experienced more
physical symptoms, including headaches, congested noses, and back pain.

Another field study involved 32 commercial pilots flying long-haul (\> 8
hrs) trips that crossed up to eight time zones per 24 hours^9^. Overall,
the average duty period was 9.8 hours long with an average layover of
24.8 hours. On two-thirds of the layovers, crewmembers slept twice,
though they still averaged 49 minutes less than their pre-trip amount.

Circadian consequences of time zone crossings were evident in a variety
of measures. Their circadian cycle moved to a 25.6 hr period, and about
20% of crewmembers had no discernable circadian temperature pattern.
Overall, the circadian cycle did not synchronize to the continual time
zone changes. There was more sleep loss associated with night flights
compared to day flights. Pilots reported consuming more caffeine and
snacks, but ate fewer meals during the trip schedule. Pilots had more
somatic complaints, including headaches, congested noses, and back pain
during trips. Logbook data and observer notes indicated that 11 % of
flight crewmembers took a nap on the flight deck when conditions
permitted.

A NASA study was conducted on 34 B-727 commercial pilots flying an 8-day
overnight cargo schedule^10^. The schedules involved crossing no more
than 8 time zones per 24 hours. Total sleep during trips averaged 1.2
hours less than pre-trip amounts, and the day sleeps were rated as
poorer than nighttime sleep episodes. Altogether, 54% of crewmembers
averaged more than one hour of sleep loss per 24 hours, and 29% of
crewmembers lost more than two hours per 24 hours, across the 8-day
schedule. All-night flight schedules did not result in a significant
circadian shift (e.g., a shift toward alertness at night and sleep
during the day), since there was only about a three-hour phase delay
(i.e., instead of a circadian nadir at 4 AM, it moved to about 7 AM).
Pilots consumed more snacks and experienced more physical symptoms, such
as congested noses, headaches, and burning eyes during trips.

There was evidence of the circadian timing system observed, e.g. the
length of morning sleep periods following an all-night duty period
coincided with the underlying circadian wake-up time.

On some long-haul flights, extra crewmembers are available to allow
pilot rest periods in onboard crew rest facilities on a rotating basis.
Flight crew members (N=1404) completed a survey at three different
commercial airlines flying several types of long-haul aircraft^11^.
Altogether, flight crew reported taking about 39.4 minutes to fall
asleep in the rest facility and averaging a total of 2.2 hours of sleep.
The crews also rated 25 factors for whether they interfered or promoted
good sleep in the crew bunk facility. The three factors that most
promoted good sleep were physiological readiness for sleep, physical
environment (e.g., bunk size, privacy), and personal comfort (e.g.,
blankets, pillows). There were five factors that most interfered with
good sleep: environmental disturbance (e.g., background noise,
turbulence), luminosity (e.g., lighting), personal disturbances (e.g.,
bathroom trips, random thoughts), environmental discomfort (e.g., low
humidity, cold), and interpersonal disturbances (e.g., bunk partner).

Case Studies in Aviation Accidents:

The societal risks associated with human fatigue engendered by around
the clock operations have been observed in a variety of ways. Fatigue
has been identified as causal or contributory in multiple high-profile
accidents. For example, official accident investigations have identified
fatigue as causal or contributory in the Exxon Valdez grounding,
Chernobyl nuclear accident, and the Space Shuttle Challenger.

In Guantanamo Bay, Cuba, in 1993, the crash of a DC-8 after a controlled
flight into the terrain was attributed to \"the impaired judgment,
decision-making, and flying abilities of the captain and flight crew due
to the effects of fatigue.\"

This occasion was the first time in history that the National
Transportation Safety Board (NTSB) cited fatigue as a causal factor in a
major U.S. aviation accident^12^. However, since then, there have been
other cases with similar determinations. The NTSB ultimately ruled that
a 1995 crash of another DC-8, which resulted in the deaths of three crew
members, was in part a result of inadequate crew rest before the
flight^13^. Authorities also found that fatigue contributed to the 1997
crash of Korean Air Flight 801, in which 228 people were killed when
their Boeing 747 collided with a hillside five miles from the end of a
runway in Guam^14^.

Additionally, after the 1999 Little Rock, Arkansas, crash of American
Airlines Flight 1420, the NTSB found that aircrew fatigue was a
contributing factor^15^. Eleven people died in this plane manned by
pilots who reportedly had been on duty for more than 13 hours; the first
officer had been awake more than 16 hours the day of the accident.
Although a tragic event, one positive result from this crash has been a
renewed interest in reviewing the adequacy of current flight-time
limitations with some consideration toward developing new
hours-of-service regulations for aviators. The flight and duty time
rules currently on the books were revised in 1985, but the basic tenets
originate in the 1940s.

**[SLEEP DISORDERS]{.underline}**

Many factors can significantly affect sleep quantity and quality, but
three deserve particular attention: age, alcohol, and sleep disorders.
Dramatic changes in sleep occur as a normal function of the aging
process. Stages 1 and 2 of non-Rapid Eye Movement Sleep (NREM) comprise
over half of sleep after childhood and are the lightest stages of sleep.
Stages 3 and 4 of NREM (also called deep NREM, delta or slow wave sleep)
and rapid eye movement (REM) sleep comprise the remainder of the sleep
and are considered the most restorative stages.

When approaching age 50 and older, five sleep-related changes typically
occur: 1) There is a significant reduction in deep sleep, with some data
suggesting that non-rapid-eye-movement (NREM) sleep stages 3 and 4
decreases or possibly disappears in the elderly. 2) There are more
frequent awakenings during sleep, so that sleep is disrupted and quality
is reduced. 3) Sleep becomes less consolidated, and it becomes
increasingly difficult to obtain the same quantity and quality of sleep
that was enjoyed when younger. 4) The ability to tolerate shiftwork
declines, and, 5) Most sleep disorders increase in prevalence and
severity with age.

Aggravating things, the most widely used sleep aid in America is
alcohol**,** yet it can disrupt both that quantity and quality of
sleep^16^. The specific amount of alcohol needed to disrupt sleep is
dependent on a variety of factors, such as body mass and tolerance.
However, the general effect is due to alcohol\'s potent suppression of
the nervous system in the first half of sleep. As the alcohol is
metabolized, rebound CNS excitability is seen and REM rebound occurs in
the second half of the night, causing awakenings to occur more often.
Nocturia is also increased. Therefore, alcohol consumed with the
intention of promoting good sleep can instead reduce both the quantity
and quality of sleep.

Yearly, at least a third of the adult U.S. population will complain
about a sleep disturbance. There are a variety of physiological and
psychological causes for these disorders. Often the sleeper is unaware
of the disorder, and complaints may focus on disturbed nocturnal sleep
or decreased waking function (e.g., sleepiness or performance problems).
Many sleep disorders can be effectively diagnosed and treated at
specialized sleep disorder centers by board-certified sleep experts.

Recognition and treatment of sleep disorders may lower the rate of
aviation accidents and improve operational effectiveness.

**Obstructive Sleep Apnea**^17^

One sleep disorder receiving particular attention in operational
settings is sleep apnea. Sleep apnea patients often complain of
excessive daytime sleepiness. Studies have demonstrated that individuals
with sleep apnea have a two to seven times increased risk for car
crashes, but data on its role in aviation mishaps is lacking. Mild to
moderate sleep apnea can cause the performance decrement equivalent to
that of a 0.05 to 0.08-blood alcohol content^18^.

Obstructive sleep apnea (OSA) results from repetitive partial or
complete upper airway collapse upon inspiration, resulting in loud
snoring, hypoxemia, and subsequently, brief arousals. It is typically
progressive, especially with weight gain. As OSA becomes worse,
oxyhemoglobin desaturations become more frequent, longer and lower.
Hypertension may develop or worsen, especially in the morning.

The repetitive brief arousals caused by sleep apnea lead to the same
effects caused by sleep deprivation. OSA patients typically complain of
daytime fatigue, sleepiness, morning tiredness, concentration
impairment, memory impairment, and irritability. Nocturia,
gastroesophageal reflux and morning headaches are also common symptoms.
The amount of sleep required to maintain function may begin to increase.
As in sleep-deprived individuals, those having OSA may tend to deny or
underestimate the extent of impairment caused by the illness.

Obstructive Sleep Apnea is caused by multiple airway anatomical and
medical problems. Allergic rhinitis, nasal septal deformity, nasal
polyps, maxillary hypoplasia, micrognathia, retrognathia, soft palate
elongation, adenotonsillar hypertrophy, and other causes of airway
reduction contribute to the development of OSA. All must be considered
and addressed if the illness is to be effectively treated. This disorder
should also be viewed as a chronic and relapsing illness, needing
periodic reassessment. Before treatment is attempted, OSA should be
verified and the severity quantified by polysomnography. There is wide
variation in individual impairment caused by OSA, and the true severity
of the illness is not predictable based on history alone. The patient's
report of improvement following treatment interventions is not reliable,
due to partial treatment response, placebo effects and fear of loss of
occupation or benefits. The Multiple Wakefulness Test, a modification of
the Multiple Sleep

Latency Test, assesses the ability to stay awake. It is probably less
useful than sleep testing during real and simulated driving and piloting
tasks, but the lack of simulator testing availability and validated
measures of fitness for duty makes the MWT the most widely used
assessment for alertness.

Weight loss is helpful in obese OSA persons, but unfortunately the
recidivism rate is high. Airway devices or surgical correction are
usually needed to correct the disorder. The devices offer rapidity of
treatment, reversibility, flexibility, low risk and low cost when
compared to surgeries. Compliance problems, unpredictable effectiveness,
and the possibility of relapse limit both surgical and non-surgical
approaches.

Nasal Continuous Positive Airway Pressure (CPAP) is highly effective,
however, compliance can be a problem. Nasal occlusion, drying,
claustrophobia, discomfort, and rhinitis often interfere with its use.
Oral appliances that protrude the mandible are effective in mild to
moderate cases of sleep apnea, and can be used in most operational
situations.

Nasal septal repair, turbinate reduction, and nasal polypectomy together
or alone are important adjunctive surgical treatments, but are rarely
curative when done without surgeries to enlarge the oropharynx and/or
hypopharynx. Even uvulopalatoplasty (UPP), currently the most commonly
performed procedure for OSA treatment, is successful much less than 50%
of the time when strict criteria (respiratory disturbance index of \<10)
for cure are used. The effectiveness of UPP is lower in the obese or
those with multiple airway anatomical problems.

Concomitantly performing a genial advancement can increase the chance of
cure. Maxillomandibular advancement is usually performed after UPP has
failed, but may be done as the primary procedure in some individuals
with maxillofacial problems. Glossectomy, hyoid suspension, and hyoid
anchoring may pose more risk of morbidity. In-office surgical procedures
that minimally alter the airway are unlikely to help OSA. Radiofrequency
Volumetric Tissue Reduction (RFVTR) applied to the tongue base has the
potential of being an additional assist in the treatment of OSA, but
still needs further investigation.

**Narcolepsy**^19^

An uncommon neurological illness, narcolepsy most often begins in youth.
It most cases, the sleepiness is extremely severe and pervasive.
Afflicted individuals often report the inability to stay awake even in
the most stimulating circumstances. Difficulty awakening in the morning
is common. Sleep attacks, or irresistible urges to sleep, are
characteristic and are often aborted or prevented by naps of less than
30 minutes. Narcoleptics often report dreaming during naps. Cataplexy, a
sudden weakness of voluntary muscles lasting up to five minutes, is
brought on by emotions such as laughter, anger or excitement.

There is no associated dizziness, or post-event fatigue. The weakness
can be generalized or affect specific muscle groups. Sleep paralysis can
occur in narcolepsy. The patient awakens fully, yet is unable to move
for a few seconds or minutes. Hallucinations are common in the
transition into and out of sleep. Cataplexy, sleep paralysis and
hallucinations are not always present in narcoleptics. The symptoms are
all manifestations of aberrant control of REM sleep related processes.

Only partial and temporary control of the sleepiness can be achieved
with stimulants such as modafanil, pemoline, methylphenidate and
amphetamines. Cataplexy, sleep paralysis and hypnagogic hallucinations
are improved by antidepressants and gamma hydroxybutyrate (sodium
oxybate), but these medications are prohibited for certain occupations.

Following an overnight polysomnogram to verify adequate sleep and
absence of sleep pathologies that could cause sleepiness and REM sleep
onsets during the nap trials, the diagnosis of narcolepsy is made by
performing a multiple sleep latency test (MSLT). Two or more REM sleep
onsets with evidence of pathological sleepiness are desirable to confirm
the diagnosis.

The MSLT is a better measure of the ability to sleep than the ability to
stay awake; therefore it should not be used as a test for ability to
maintain alertness or vigilance. Genetic testing for narcolepsy is not
diagnostic, but there is a genetic predisposition for the disorder. For
most afflicted individuals, the cause of narcolepsy is now believed to
be due to autoimmune-caused degeneration of CNS hypocretin-orexin cells,
triggered by unknown environmental causes in susceptible individuals.
Deficiency of hypocretin/orexin may be commercially measurable in the
near future, adding another diagnostic tool for the evaluation of
narcolepsy.

**Insomnia**^20^

Chronic insomnia affects 10 to 30% of the population. Its prevalence and
importance in the aviation population is less certain. Studies of
performance in chronic insomniacs have given mixed results, but more
recent studies suggest that performance impairments and increased
accidents do occur as a result. Insomnia is a complaint that may have
multiple causes.

Insomnia due to anxiety and depression, for example, has more bearing on
flight operations than insomnia due to sleep state misperception, in
which there is adequate sleep, but impaired ability to perceive that
sleep has occurred. More senior flight personnel have more difficulty
adapting to unfamiliar (hotel insomnia), uncomfortable, noisy, or bright
sleeping accommodations. Nearly all insomniacs develop poor sleep habits
and frustration, which may perpetuate the problem. Therefore, good sleep
habits and other behavioral techniques are essential to the effective
treatment of insomnia.

Good Sleep Habits

-   Use the bed for sleep only\-\--avoid watching TV, music, business,
    arguing in bed.

-   Avoid looking at the time.

-   Avoid alcohol, caffeine, and heavy meals 3 hrs before bed.

-   Schedule a worry time, planning session, and wind-down time before
    getting into bed.

-   Make lists of things to do the next day, but not in bedroom.

-   Make the bedroom quiet, comfortable, dark and secure. Use white
    noise generators that make a fanlike noise if the environment is
    noisy. No radios, waterfalls, birds, etc. Minimize disruptions, e.g.
    pets.

-   Get out of bed after lying awake for more than 20 minutes\-\--do
    something boring or run through relaxation techniques.

-   Avoid exercise and hot baths within 3 hours of bedtime.

-   Exercise (aerobic) regularly, in the morning or afternoon.

-   Keep a regular bedtime and get up time even on days off.

-   Do not spend excessive amounts of time in bed, e.g., if you can
    sleep only 7 hours, spend no more than 7.5 hours in bed.

-   Avoid excessive napping, which can interfere with the ability to
    sleep at night.

**Restless Legs Syndrome**^21^

In addition to psychological causes of insomnia, physical disorders also
commonly contribute to insomnia. Restless legs syndrome (RLS) is an
annoying but non-painful condition, which usually manifests itself in
the evening hours, or with prolonged sitting or lying. It is an
extremely common cause of insomnia, ranging from 6 to 13% of men and 10
to 17% of women. Involuntary jerks and twitches are frequently observed
while awake, and usually there are rhythmic leg jerks occurring about
every 20-40 seconds after sleep onset (periodic limb movements of sleep
(PLMS).

The afflicted individual experiences an overwhelming need to move the
legs, which gives temporary relief. Caffeine, alcohol, anticholinergic
medicines, antihistamines, antidepressants, antipsychotics, diuretics,
decongestants, and theophylline can aggravate the condition.

Iron deficiency, anemia, uremia, vitamin deficiencies and electrolyte
abnormalities can aggravate RLS. Iron supplements have been reported
helpful, but because of the risk of iron overload disorders it is
recommended that ferritin and iron panels be obtained and followed. A
number of drugs have been reported effective in small case studies.
Clonazepam, dopamine agonists (levodopa, bromocriptine, pergolide,
pramipexole) and narcotic analgesics have been demonstrated to be the
most effective, but the habituating medications are contraindicated for
flight duty.

**[FATIGUE COUNTERMEASURES]{.underline}**

Some widely held yet inaccurate assumptions about fatigue and circadian
rhythms are problematic or dangerous when they are applied to aircrew
scheduling practices. Dinges^22^ identified six myths that are
particularly hazardous in aviation operations:

**Myth 1.** If an airframe can be readied for service at a moment\'s
notice, day or night, the pilot should be ready to go as well.

**Myth 2**. Good aircraft maintenance will ensure a high degree of
operational safety.

**Myth 3**. A high degree of training, combined with past experience
with sleep deprivation and shift work, is the key to avoiding
performance problems associated with fatigue from overwork and rotating
duty schedules.

**Myth 4**. Increased payer rewards can overcome fatigue by increasing
the motivation of sleepy crews

**Myth 5.** Determining how much rest or sleep employees will need to
avoid performance problems is a straightforward matter when establishing
new work/rest schedules

**Myth 6**. Some people believe that fatigue really shouldn\'t be a
concern because fatigued aircrews often safely complete trips without
having accidents.

Dinges pointed out the imperative of dispelling these myths at the
management and operational levels of any organization. Properly dealing
with these issues could save lives by improving both safety and
performance. Managers must make a concerted effort to educate themselves
and their employees about the nature and effects of fatigue, support
efforts to enhance an understanding of fatigue-related problems, and
develop effective and feasible countermeasures.

Current and future job demands (long work hours and irregular work
schedules) are likely to continue or possibly even worsen, therefore
pilots, crews, and management must be prepared to effectively deal with
fatigue to sustain productivity, safety, and personal well being.
Unfortunately, this goal is made difficult because sufficient knowledge
about the causes of fatigue, the impact of fatigue on performance in
individuals, and the types of strategies that are effective for
controlling fatigue in flight operations are lacking.

It has been suggested that breaks improve performance by allowing
physiological recovery, reducing boredom, and increasing worker
satisfaction. The Hawthorne experiments indicated that job performance
and productivity improved when work breaks were introduced. Angus^23^
reported that breaks were beneficial for temporarily overcoming fatigue
in sustained operations. On the other hand, activity breaks have been
evaluated to determine their effectiveness in promoting alertness and
performance during flight operations.

Breaks

Twenty-eight pilots studied in a B747-400 simulator were involved a
6-hour uneventful night flight^24^. Pilots were provided either five
regularly scheduled 7-minute breaks (Treatment) or a single, mid-flight
break (Control), which involved getting out of their cockpit seat,
walking, and interacting socially. Pilots in the Treatment condition
showed improved subjective sleepiness ratings up to 25 minutes after the
break compared to Controls. However, the objective performance tests did
not show improved results for the Treatment vs. Control conditions and,
therefore, did not parallel the subjective findings that the pilots
reported feeling less sleepy. It is apparent that more work needs to be
done in evaluating rest breaks during daytime, night time and sleep
deprived conditions to assess the impact on flight operations.

Cockpit Rest Periods

Laboratory-based studies have demonstrated that naps can improve
performance and alertness. NASA pilot reporting data have indicated that
spontaneous, uncontrolled sleep episodes were occurring in flight.
Therefore, NASA conducted a field study to examine the effectiveness of
a planned cockpit rest period to improve pilot alertness and performance
during actual flight operations^25^. Twenty-one B747-200 flight crew
participated in the study involving a 12 day trans-Pacific trip schedule
with eight flight segments of about nine hours each, with approximately
24 hours layover between flights. Group 1 was allowed a 40-minute
planned in-flight cockpit nap opportunity during a single flight
segment, one crewmember at a time on a predetermined rotation (Nap
Group). Group 2 had a 40 minute control condition identified, but were
not allowed to nap during that time (Control Group). Both groups had the
same measures performed, including subjective sleep/wake diaries,
physiological measures of brain and eye movement activity (i.e. EEG,
EOG), and vigilance performance using a sustained attention task.

On average, using standard EEG criteria, the Group 1 (Nappers) fell
asleep in 5.6 minutes and slept for 25.6 minutes. Overall, there was a
34% improvement in performance for Group 1compared to Group 2 (Controls)
and a 54% improvement in physiological measures of alertness during the
last 90 minutes of flight. Overall, the Control Group had 120
\"microsleeps\" of five seconds or longer during that time, including 22
during the final 30 minutes of flight that involves touchdown. The
Nappers had a total of 34 micros1eeps, with none occurring during the
final descent and landing phase of flight. Importantly, there were no
differences in the subjective ratings of alertness between groups,
though the objective performance and physiological alertness measures
showed significant improvements in the Nappers.

Proper flight schedules

Because subjective complaints of sleepiness, fatigue-related performance
problems, and physiological indices of impaired alertness have been
shown to be particularly problematic for personnel who work
(physiological) nights and early mornings. One of the most obvious
countermeasures for fatigue is to minimize the amount of work occurring
at these times^26^. Because this solution usually is not possible, every
effort should be made to construct duty schedules that allow sufficient
time for sleep between work periods, eliminate double shifts, shorten
the length of flights, schedule work periods that ensure people have
opportunities to sleep at the most conducive times of day (sleep occurs
more easily during the late night/early morning and mid-afternoon), and
develop fixed shifts. Rotating shifts, regardless of how they rotate
(day-to-evening-to-night, or day-to-night-to-evening) are the most
disruptive.

Sufficient sleep

The most effective strategy for minimizing fatigue on the job is to
ensure adequate sleep before the duty period. Research has shown that
sleep restriction severely degrades performance in a dose-response
manner (i.e., the less sleep, the greater the performance
decrement)^5,27^. Although it has been suggested that five hours of
sleep per night may be sufficient to maintain normal functioning,
performance and alertness deteriorate after restricting sleep to six
hours per night, and uncontrolled sleep attacks occur when only four
hours of sleep per night are allowed. Although personnel may think they
can adjust to chronic sleep restriction, no objective proof
substantiates this belief.

Currently, at least seven hours of sleep per day appears to be the
minimum required to sustain adequate alertness in most people. However,
sleep needs vary widely, and individual requirements range from about
four to ten hours. To determine how much sleep is necessary to maintain
daily alertness, crewmembers should adjust the amount of sleep they
receive gradually and adhere to any new schedule for about 1 week before
deciding whether more nightly sleep is needed. The focus should be on
how much sleep is necessary to remain awake in sedentary situations,
such as watching television, reading, riding in a car, attending
meetings, driving, and performing routine work, because these are the
types of situations in which physiological sleepiness most likely
becomes evident. Also, staying awake in the afternoons often is more
difficult than at other times of the day, especially if chronic sleep
restriction is a problem.

Naps

In situations in which sleep is disrupted frequently or missed
altogether, scheduled naps can serve as performance maintenance or a
recuperative function to attenuate fatigue until normal sleep is
possible^23,28^. This countermeasure is the best for fatigue besides
full, eight-hour periods of restful sleep. Short naps can be used to
promote alertness during long work periods that allow very little time
to sleep. Napping has been suggested as a viable fatigue countermeasure
in several situations, including aviation. Although two-hour naps are
clearly helpful in attenuating performance declines associated with
continuous work without sleep, even short naps (5-20 minutes) have been
found to enhance productivity and safety in sleep-deprived workers.

Scheduled napping of almost any duration offers a significant
performance advantage, although its efficacy is affected by a variety of
factors:

Creating a suitable nap environment is essential. A small, dark,
comfortable place where noise and distractions are minimized is best;
otherwise sleep masks, foam earplugs, or a fan can reduce environmental
sources of sleep disruption. Naps should be taken at appropriate times
in the 24-hour period because circadian rhythms affect the ability to go
to sleep (on average, whenever possible, it is best to take nighttime
naps between 1AM and 6 AM and daytime naps between 2PM and 5 PM). Naps
should be as close as possible to the beginning of the sleep deprivation
period because sleep debt should be avoided. Naps are most effective if
they occur before or soon after the start of the sleep-deprivation
period; later naps, although not optimal, can substantially recover
performance and alertness that has been lost.

Naps should be as long as possible, but keep in mind that at least 15 to
20 minutes should be allowed for sleep inertia (post-sleep grogginess)
to dissipate before returning to flight-related duties. Naps during
circadian dips are easiest to initiate but the most difficult ones from
which to awaken, and once awake, a person may take several minutes to
attain adequate alertness. Naps of 40 minutes to two hours are
recommended.

Stimulant medications

Stimulants and sedatives are currently used in U.S. military and foreign
commercial operations. There may be a role for stimulants such as
modafanil, pemoline, methylphenidate and amphetamines in defined
settings. The same is true for short and intermediate acting sedatives.
Even short-acting sedatives can impair next-day performance, however,
and reasonable concerns exist about the effect of stimulants on sleep,
emotions and performance.

Stimulants have both disadvantages and advantages related to
effectiveness, availability, abuse potential, and side effects. Caffeine
is widely available and clearly effective for attenuating sleepiness,
especially in people who don\'t normally consume large quantities^29^.
It is easily obtained (from soft drinks, coffee, and tea), and is
socially acceptable. However, it is unlikely that caffeine is sufficient
to maintain the alertness of sleep-deprived people who ingest it
frequently, and in sensitive individuals or overdoses, it can cause GI
disturbance, nervousness, tremor, irritability, headaches, and
tachycardia. Side-effects that typically occur with caffeine are also
observed with other stimulants discussed below.

Pemoline is a less well studied controlled stimulant with a slower onset
of action than that of other stimulants^30^. Also, in rare instances
pemoline has caused hepatic necrosis, and has fallen out of favor for
use in most clinical settings.

Modafinil is a new controlled stimulant that appears (at high doses) to
produce alertness levels similar to those produced by amphetamines^31^.
Because modafinil reportedly has a low abuse potential and few side
effects at lower doses, it may be an effective compound for attenuating
sleepiness in occupational settings. However, adequate studies must be
performed before modafinil is considered feasible for aviator
performance maintenance.

To date, sufficient data are not available from field settings and at
normal doses may not confer a significant advantage over caffeine^32^.

Methylphenidate is an effective stimulant that, although available for
many years, has not been extensively researched in aviation settings.
Like the amphetamines it is considered to have a high abuse potential
and is stringently regulated. Its effects on the cardiovascular system
do not appear to be as problematic as found with the amphetamines, but
more than with pemoline or modafinil.

Dextroamphetamine has been the most heavily researched stimulant on the
market. It has been available since the 1950s and has been shown
repeatedly to improve the alertness and performance of fatigued
individuals both in laboratory and field settings^33,34^.

While it appears that several compounds can stave off the effects of
fatigue, their chronic use is ill-advised because of a lack of data on
their long-term feasibility in applied situations, the potential of drug
tolerance that eventually could make the compounds ineffective, or their
known side effects. Broad reliance on the prescription stimulants is not
recommended because of the difficulty controlling administration in
civil aviation operations. Indiscriminate use will lead to abuse and
possibly addiction with all of these compounds. However, for the time
being, U.S. private pilots and flight crews are prohibited from using
medications discussed above. Therefore, other countermeasures must be
considered.

Bright light and melatonin

For shift workers, a possible option is the use of bright lights or
melatonin to resynchronize the body\'s rhythms to different work/rest
routines, especially to the night shift^35,36^. Theoretically, because
most fatigue-related decrements in performance and alertness occur on
the night shift, and many of these problems have been attributed to the
fact that the body\'s rhythms cannot effectively synchronize to night
work, any strategy that can promote adaptation to night duty should
improve nighttime performance.

The timing of light exposure exerts a major effect on circadian rhythms,
and research has shown that bright light can produce large phase shifts
when the exposure is timed in conjunction with a new sleep/wake cycle.
In its most simplified fashion, this would involve exposing personnel
changing from day shift to night shift to bright light for at least two
hours in the evening (ideally, before work, beginning at approximately 8
PM) and exposing night workers who are transitioning to the day shift to
bright light after about 9 AM. In addition, because melatonin levels
exert an effect on the body\'s clock, research has shown that proper
timing of melatonin administration may also influence the phase of the
circadian timing system.

The best time to administer melatonin is directly opposite to when
bright light exposure should occur. Therefore, day crews attempting to
adjust to the night shift should take melatonin around 9 AM (to promote
daytime sleep), and night crews attempting to transition to the day
shift should take melatonin at about 8 PM (to promote evening sleep).
The intervention times suggested above are based on assumptions about
the average timing of peaks and troughs in the body\'s temperature and
hormonal rhythms, and these are not consistent for everyone.

The only way to ensure the proper use of light and melatonin is to
evaluate each individual\'s circadian rhythms before employing such
interventions. Also, it is crucial to minimize conflicting influences
(eg, artificial bright light at night followed by sunlight exposure on
the way home from the flight line in the morning) to facilitate the
efficacy of these strategies. Although both techniques are theoretically
suitable for countering fatigue in personnel who work rotating shifts,
their application may not be feasible in most applied settings,
particularly those that employ shift rotations or compound time zone
transitions that occur within three days.

Exercise

Evidence indicates that exercise may be an effective, if only temporary,
method for increasing alertness and arousal^37^. Moderate physical
exercise has been found to improve cognitive performance on a continuous
attention task in non-sleep-deprived volunteers, and fairly stressful
exercise enhances cognitive vigilance in sleep-deprived subjects. In
addition, physiological indications of sleepiness were reduced in
sleep-deprived helicopter pilots who engaged in repeated ten-minute
bouts of moderately difficult physical activity^38^. However, it seems
that even if exercise promotes alertness in the short term, the effects
are relatively short-lived (lasting only 10-30 minutes).

Therefore, in situations where frequent exercise breaks are feasible,
the use of this countermeasure may be appropriate; however, such a
requirement no doubt will make this an unacceptable alternative in most
aviation settings. Also, it should be noted that heavy exercise,
although providing stimulation during the activity itself, may make
sleepiness and/or fatigue more pronounced later in the work period.

Temperature and noise

Two common techniques sometimes used in an attempt to improve alertness
during driving and other types of tasks are exposure to cold air and
listening to the radio. Unfortunately, little evidence supports the
efficacy of either of these strategies. Fagerstrom and Lisper^39^
reported that listening to a car radio slightly improved reaction times
in extroverted or inexperienced drivers, but Reyner and Horne^40^ found
that listening to audio tapes or radio programs had only marginal
effects on the driving performance of partially sleep-deprived subjects.

Cold air applied to the faces of these drivers was similarly
ineffective. Also, while the radio temporarily decreased ratings of
self-reported sleepiness more than the cold air, the effect was not
associated with improvements in physiological measures of alertness. The
use of either strategy is not recommended. If used at all, they should
be restricted to times when a small, temporary boost in alertness is
necessary only to inhibit fatigue until a more effective countermeasure
can be applied.

Physical fitness

Military organizations historically have sought to reduce the impact of
sustained work on personnel by ensuring high levels of physical fitness.
Although it stands to reason that fit people will be able to withstand
longer periods of physical labor, little evidence exists that the same
applies to the performance of cognitive tasks. However, Harmii et al.
found that female night workers\' subjective complaints of fatigue were
reduced after objective improvements in physical fitness^41,42^.
Unfortunately, this did not appear to translate into performance changes
on a short-term memory task. These results were partially confirmed by
Angus et al, who found that highly fit individuals were no better than
those of average fitness in sustaining intense cognitive work during
sleep deprivation^23^. Thus, physical training programs are unlikely to
effectively minimize the effects of fatigue on mental tasks.

Increasing environmental stimulation through physical activity, rest
breaks, and other techniques appears to exert beneficial effects on
alertness; however, the most effective countermeasures for fatigue are
those that minimize circadian disruptions and remedy sleep deprivation,
i.e. proper work schedules, strategic naps, and sufficient sleep
periods. Although other approaches are effective for minimizing
on-the-job sleepiness, such as avoiding shift work and relying on
pharmacological interventions, these are not feasible in most aviation
settings.

Specific Recommendations for Aircrews, Groundcrews and Air Traffic
Controllers

Applying the previously discussed fatigue-management principles to
improve the alertness of pilots and crews requires minor modifications
because of their unique work situations. However, these same basic
integrated strategies are applicable across a variety of settings.

**Adhere to a consistent sleep routine even on days off**

This means that aviation personnel (especially those working nights)
should avoid reverting to a daytime schedule during the weekends or on
days off. Also, they should not sleep longer than usual on non-work
days. Either of these behaviors can have a deleterious effect on
performance because they upset the body's biologic clock or lead to
sleep difficulties or fatigue problems later on.

Get the best sleep possible in advance of any trip (or long work shift)

Family and friends should be kept informed about work schedules so they
can avoid interrupting the sleep period. Crew members themselves should
take several actions to maximize their sleep quality, such as making
sure the bedroom is cool, dark, and comfortable; minimizing distracting
noise by unplugging the telephone, disconnecting the doorbell, and using
a fan or earplugs to cover sleep-disrupting sounds; and avoiding
smoking, caffeinated drinks, and alcohol before bedtime because these
can disturb sleep. Also, they should avoid medications that contain
caffeine.

If possible, take a nap immediately before a work shift (especially a
night shift)

One of the primary determinants of sleepiness is the amount of time that
has elapsed between the duty period and the last sleep period. Naps
lasting from 40 minutes to two or four hours are known to be helpful as
long as enough time is allowed for sleep inertia to dissipate on
awakening (15 to 20 minutes should be sufficient). As was mentioned
earlier, some of the best times for naps are between 1 and 6 AM or 2 to
5 PM because sleep occurs more easily at those times.

Minimize boredom

Sedentary activities tend to make people sleepy, so efforts should be
made to increase environmental stimulation. Although most of these
strategies are only minimally effective, it might be helpful when
possible to do brief shoulder, arm, or leg stretches; engage in
conversation; and take breaks whenever the opportunity arises. However,
remember that any of these techniques cannot be expected to help for
more than a few minutes. So if sleepiness becomes a problem, the only
really effective strategy is to take a nap (perhaps between flights).

When alertness begins to deteriorate, use caffeine for a temporary boost

A typical cup of coffee has about 100 mg of caffeine, and research has
shown that 200mg doses can help reduce sleepiness temporarily. Tea and
many soft drinks also contain caffeine but less than the amount found in
coffee. Although caffeine is an effective stimulant, it is important to
remember that the more someone normally uses caffeine, the less
effective it will be. The alerting effects take a while to begin (30
minutes to an hour), and they may not last for more than an hour or two.
Caffeine should not be considered a replacement for sleep. Naps are far
more effective in the long run. Naps are defined as intentional sleep
lasting less than half the length of the major sleep period.

[Concluding Remarks]{.underline}

Society has increasingly changed sleep amount expectations and work
demand to 24/7 operations causing sleep disruption and reduction.
Extensive research into fatigue by the DOT and DOD has yielded important
information about the resulting desynchronoses and techniques to improve
performance and safety during prolonged and/or nighttime flying and
shiftwork. Basic principles to keep in mind are summarized below.

What Aerospace Personnel can do:

-   Do not overwork or under-sleep before flying

-   Take naps before and at the beginning of flights at night to improve
    performance during and at the end.

-   Get two nights of normal sleep before to improve performance before
    beginning night flying or continuous operations.

-   Get two nights of normal sleep at the end of an operation to recover
    from the effects of sleep deprivation.

-   When on night shift or flying across multiple time zones, take naps
    during the day, especially in the mid-afternoon sleepiness phase.

-   Realize that naps are a stopgap approach to improve performance and
    safety for limited periods of time, not an indefinite substitute for
    long sleep periods during biological night.

-   Attempt to anchor sleep when sleeping in a different time zone by
    getting some of the sleep during home base sleeping hours.

-   Remember, the longer the nap, the better the improvement in
    performance.

-   Also remember, the longer the nap, the longer it takes to awaken
    (more sleep inertia). At least 20 minutes should be allowed to
    awaken from a nap to allow dissipation of sleep inertia.

-   When possible, engage in conversation, stretch and move about to
    improve alertness.

-   Use caffeine to help maintain alertness, but keep in mind that it
    will disrupt sleep if used too close to your desired sleep time.

-   Alcohol use may interfere with sleep quality and
    performance\-\--avoid it when working shifts or in the days leading
    up to night operations.

-   Learn and use relaxation techniques and sleep hygiene to assist
    napping and adjustment to new circadian schedules.

-   Maintain a meal schedule with healthy and nutritional food to
    minimize gastrointestinal problems associated with night operations.

-   Recognize the signs of sleepiness in yourself and your crew. Speak
    up when you or your crew need rest or sleep.

-   If you have reached the point that you think you cannot cope
    adequately with changing schedules, consider reassignment or a
    different occupation.

-   If you have a sleep disorder, seek treatment.

-   What Employers of Aerospace Personnel can do:

-   Minimize night flights and rotating shifts; institute fixed shifts
    in place of rotating shifts

-   Keep duration of operations for any single operator to less than ten
    continuous hours

-   Tailor the length of duty to the strenuousness of the operation
    (e.g. air rescue, combat, rotary wing operations should have fewer
    hours on duty than transport operations)

-   Provide sleeping environments as free from noise, light, temperature
    extremes, and interruptions as possible.

-   Lying down and sleeping is more beneficial than trying to sleep
    chest elevated, therefore, provide sleeping arrangements for crews
    that allow the best sleeping position.

-   Provide one or two nights off in a long series of night operations
    to help restore function.

-   Allow at least 2 days between completed night flights and shift
    transitions in normal, non-urgent operations

-   Sanction and support napping before and during night and
    transmeridian flight operations, especially the longer and harder
    ones.

-   Adjust the length of the naps allowed and the amount of time needed
    to get over sleep inertia based on the amount of sleep loss and
    circadian disruption incurred.

-   Assess individual crewmembers' ability to tolerate shiftwork and
    jetlag, particularly as they age. Try to fit duty schedule to
    ability to function.

-   Identify sleep disorders in personnel and facilitate effective
    treatment.

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