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The International Journal of Applied Aviation Studies 244
International Journal of Applied Aviation Studies, Volume 7, Number 2
Copyright © 2007, FAA Academy, Oklahoma City, OK
Requests for reprints should be sent to Kay Chisholm, FAA Academy, AMA-530-D, P.O. Box 25082,
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The International Journal of Applied Aviation Studies 244
The Effects of Low Dose Caffeine on Pilot Performance
Tom J. Caska
and
Brett RC. Molesworth
University of New South Wales
Department of Aviation
UNSW Sydney NSW 2052
b.molesworth@unsw.edu.au
+61 2 9385 6757 (Telephone)
+61 2 9385 6637 (Facsimile)
Abstract
Pilots often use caffeine, in the form of coffee, during critical phases of flight to enhance
performance. This study investigates the effects of low dose caffeine on pilots’ perfor-
mance during a crucial segment of flight. Thirty pilots were randomly divided into three
groups (0mg/kg, 1mg/kg, & 3mg/kg of caffeine). The pilots performed two simulated in-
strument landing systems approaches. Caffeine was administered between the two flights
and pilots’ performances were measured and compared. The results failed to reveal any
differences between the three groups. In contrast, a group by sleep interaction was signifi-
cant. The results suggest for a normal well-rested person, caffeine at relatively low doses,
similar to that used by pilots, has no measurable effect on performance. In contrast, for a
person not well rested, caffeine in low doses noticeably improves performance. Results
are discussed from an applied perspective and alternate methods of enhancing perfor-
mance are reviewed. Recommendations are made for future studies in this field.
Throughout the history of aviation, human error has been the causal factor of
many accidents and incidents worldwide (Nagel, 1988). Certain phases of ight
pose greater risks than others, for example the descent, approach, and landing
phases of ight (Graeber, 1988). According to Boeing’s statistical summary of
commercial jet airplane accidents from 1959 to 2005, the greatest number of fatal
accidents occurred during the landing phase of ight (Boeing, 2006). The major
contributing factor to these incidents was cited as ‘crew error’ or otherwise known
as ‘human error’.
During critical phases of ight, such as landing, the pilot and crew experience
high workloads and are often required to make rapid decisions with a high level
of accuracy. They are also required to be cognisant of their surrounding, including
The International Journal of Applied Aviation Studies
245
the performance of the aircraft and any other aircraft in the vicinity, while at the
same time perform numerous other tasks crucial to the ight. Attention to detail
and high levels of concentration are critical to the operation. However, after a long
and potentially fatiguing trans-continental ight or a busy domestic schedule, the
pilot and crew may nd that they are unable to perform their usual duties with the
same degree of accuracy and efciency (Caldwell, 1997). This scenario can be
further intensied with increasing workload during an instrument approach in bad
weather or with unforseen circumstances. To help combat these particular
situations, pilots often employ various coping strategies such as planning energy
use, active coping, mental withdrawal, communicating with other crew members,
and coffee drinking (Petrie & Dawson, 1997). It is the latter of these coping
strategies that is the focus on this research, and specically how caffeine at low
doses improves pilots’ performance.
According to Petrie and Dawson, (1997) and Caldwell, (1997) caffeine is widely
used to help alleviate the symptoms of fatigue and increase alertness. While coping
strategies such as planning energy expenditure, and active coping are more
effective than caffeine over the longer term (Petrie & Dawson, 1997), anecdotal
evidence derived from the aviation industry suggests that the availability and
immediacy of caffeine makes it an attractive contingency for those situations
involving unpredictable high workload or less than ideal planning.
Caffeine intake by pilots generally occurs through drinking coffee or tea, and
to a lesser extent through the consumption of cola or energy beverages. A typical
serving of coffee or tea contains between 30 and 120 mg of caffeine, while cola
based drinks contain between 20 and 90 mg of caffeine per serving (Segall, 2000;
D’Anci & Kanarek, 2006) (see Table 1 for typical caffeine content per 12oz serving
for an individual weighing 176lb). In the case of coffee, the quantity of caffeine per
serving can vary dramatically based on the duration in which the coffee has been
roasted and the way the beverage has been brewed. In terms of the duration of
roast, the lighter roasts, which have been roasted for a short duration, contain
signicantly more caffeine than the darker roasts, which have been roasted for a
longer duration (D’Anci & Kanarek, 2006).
Table 1
Caffeine content per 12oz serving for an individual weighing 176lb/80kg.
Product
Caffeine per
12oz/340mls
serve (mg)
Equivalent servings for an 176lb/80kg person
(cups)
Experimental Groups
0 mg/kg 1 mg/kg 3 mg/kg
Coffee
Brewed 200 0 0.4 1.2
Instant 30-120 0 2.6 - 0.6 8.0 - 2.0
Tea
Leaf or
bag 30-120 0 2.6 - 0.6 8.0 - 2.0
Cola beverage `
Regular 30-90 0 2.6 - 0.8 8.0 - 2.6
Diet 39-50 0 2.1 - 1.6 6.2 - 4.8
Effects of Caffeine on Pilot Performance 246
According to Fredholm, Battig, Holmen, Nehlig, and Zvartau, (1999) caffeine
is the most widely consumed behaviourally active substance in the world. Caffeine,
while common to many widely consumed drinks including tea, coffee, cola
beverages and some energy drinks, it is also present in some foods including,
chocolate and certain candies. Caffeine can even be found in some medicines
such as non-narcotic analgesics including aspirin (Daly, 1993).
While the vast majority of the empirical research examining the effects of
moderate to high dose caffeine use (between 4 and 7 milligrams per kilogram) on
human behaviour concludes in favour of the drug for enhancing performance
such as vigilance (Smith, Kendrick, Maben, & Salmon, 1994), sustained attention
(Smith et al., 1994), mood (Herz, 1999), self-rate alertness (Kohler, Pavy, Van
Den Heuvel, 2006), physical performance, (McLellan, Bell, & Kamimori, 2004;
Tucha, Walitza, Mecklinger, Stasik, Sontag, & Lang, 2006; Wiles, Coleman, Teg-
erdine, & Swaine, 2006) and decision-making (Lyvers, Brooks, & Matica, 2004),
research examining its effect at low dosages, typically what is consumed by pilots
appears less conclusive. Specically, while Smit and Rogers (2000) found that as
little as 12.5mg of caffeine can signicantly improve cognitive performance
(reaction time, rapid visual information processing), and mood amongst subjects
from the general population, Gillingham, Keef, Keillor, and Tikusis, (2003) found
that 300mg of caffeine had no effect upon marksmanship accuracy and precision
with military reservists. The inconsistency in results between low dose caffeine
studies are further illustrated by Lieberman, Wurtman, Emde, Roberts, and
Coviella, (1987) who found that as little as 32mg of caffeine signicantly improved
auditory vigilance and visual reaction time with healthy male subjects, while Tucha
et al., (2006) found that 1.5mg/kg or 3.0mg/kg of caffeine failed to improve hand
writing dexterity in right handed adults.
In contrast to the mixed results pertaining to the effects of caffeine at low
doses under normal operating conditions, studies, which involve the administration
of caffeine under conditions where participants experience sleep deprivation or
exposure to severe environmental and operational stress, repeatedly demonstrate
the benecial effects of caffeine in a dose-dependent manner (Lieberman,
Tharion, Skukitt-Hale, Speckman, & Tulley, 2002; Kamimore, Johnson, Thorne, &
Belenky, 2005; McLellan et al., 2004). Specically, Lieberman et al. (2002) found
that the administration of 100, 200, or 300mg of caffeine following 72 hours of
sleep deprivation to US Navy Seal trainees mitigated many of the adverse effects
associated with the lack of sleep. According to Lieberman et al. (2002) the most
notable improvements occurred with visual vigilance, choice reaction time, and
alertness in a dose-dependent manner.
Caffeine administered in repeated dosages throughout the day has also been
shown to consistently improve performance (Brice & Smith, 2002; Hindmarch,
Rigney, Stanley, Quinlan, Rycroft, & Lane, 2000). Moreover, Brice and Smith
demonstrated that four 65mg doses of caffeine over a ve hour period (1000,
1100, 1200, and 1300 hours) is consistent with one 200mg dose in terms of
improving alertness and performance on simple and choice reactive tasks, as
well as more complex dual tasks involving tracking and target detection.
The International Journal of Applied Aviation Studies
247
Caffeine affects the central nervous system and alters brain functions on both
a molecular and cellular level (Daly, 1993). Caffeine achieves this by acting as an
antagonist at adenosine receptors. Adenosine receptors are found throughout the
body including the heart, gastrointestinal tract, blood, and respiratory system.
Adenosine receptors are responsible for the uptake and transmission of adenosine.
Adenosine is formed during the breakdown of adenosine triphosphate and is said
to be the primary energy source for the majority of the cells in the human body
(D’Anci & Kanarek, 2006). Adenosine is considered to be a neuromodulator, which
achieves its behavioural effect by “inhibiting the conduction of messages at
synapses that use other neurotransmitters such as dopamine and norephinephrine”
(D’Anci & Kanarek, 2006. p189). Therefore, caffeine can be described as a drug
that cancels out the neuromodulatory effect of adenosine, hence causing an
increase in the stimulation of neuronal activity which in turn results in increased
heart rate, blood pressure and a reduction in the feeling of fatigue.
Once consumed, the peak effect of caffeine generally occurs within 15 minutes
and in some cases may take 2 hours (Arnaud, 1993; D’Anci & Kanarek, 2006). The
half-life of caffeine varies among individuals, and is about 3 to 7 hours in healthy
adults (D’Anci & Kanarek, 2006). In regular caffeine users, the positive stimulant
effects of caffeine can be reversed in the short term if the use of the drug is ceased.
Mild withdrawal symptoms of caffeine can include headaches, irritability, mental
confusion, nervousness, reduction in energy, and fatigue (D’Anci & Kanarek, 2006;
Daly, 1993). Typically, these symptoms begin 12 to 24 hours after the last
administration of the drug (Dews, O’Broem, & Bergman, 2002). According to Smit
and Rogers, (2000) studies that examine the effects of caffeine on performance,
where participants are required to abstain from consuming caffeine for an excess
of 12 hours prior to the research, may not fully be aware if the results obtained
were due to the effects of caffeine, or a reversal of the negative consequences of
caffeine withdrawal.
The purpose of the current study was to examine the impact of caffeine on
pilots’ performance under conditions that reected as much as possible, those
commonly experienced by pilots. Therefore, only caffeine in dosages equivalent to
that typically consumed on the ight deck was investigated (between one and
three cups). Furthermore, since anecdotal evidence suggests that pilots tend to
consume caffeine directly prior to a crucial phase of ight such as at the top of
descent, the effects of caffeine was investigated within a time frame reective of
this environment (between 20 and 30 minutes from touchdown). Since caffeine
withdrawal has also been identied as a factor that impacts on the results of
caffeine based studies, all participants were asked to abstain from consuming
caffeine products for a period of six hours prior to the research. In addition, the
conditions surrounding the experiment were controlled, as much as possible, to
ensure the pilot participants were not sleep deprived or fatigued. Finally, as part of
the recruitment process, and solely for ethical reasons, all potential participants
were informed prior to the study that the research was concerned with the effects
of caffeine on pilots’ performance. While providing participants information about
the purpose of the study is not unique to this research (see Kamimore et al., 2005;
Smit & Rogers, 2000; Lyvers et al., 2004; Tucha et al., 2006), it is important to
acknowledge that this may have inuenced participants, resulting in a ‘placebo
effect’. Nevertheless, the researchers viewed the potential risk of this occurring to
248
be signicantly less than the risk associated with administering a drug (i.e., irreg-
ular heartbeats (arrhythmia), increase blood pressure, respiratory problems, renal
and nervous system problems (Daly, 1993; D’Anci & Kanarek, 2006)) albeit legal,
to unsuspecting participants.
Employing a between-subjects repeated measures experimental design,
pilots were asked to y two simulated Instrument Landings Systems (ILS)
approaches with the administration of caffeine occurring between the two ights.
Data relating to pilots’ performance in terms of mean deviation from the glide path
both horizontally and vertically were calculated and then compared between the
two ights.
Method
Participants
Thirty participants were recruited from the University of New South Wales
Aviation ight training school and various other ight training schools located at
Bankstown airport. All participants were required to hold a current Class 1 Avia-
tion Medical Certicate, indicating they were medically t for ying. The partici-
pants were randomly divided into three groups (0mg/kg, 1mg/kg, & 3mg/kg). The
mean age was 23.13 (SD = 4.21) years and the mean total ight experience was
704.53 (SD = 1125.85) and the mean total instrument ying experience was 47.67
(SD = 108.43). In order to determine if there were any differences between the
three groups in terms of age or ight experience, a series of univariate analyses
of variance were conducted. With alpha set a .05, the results of a univariate
analysis of variance failed to reveal any statistically signicant differences between
groups in terms of age F(2,27) = .065, p= .937, η2 = .005, total hours ying expe-
rience F(2, 27) = .095, p = .910, η2 = .007, and total instrument ying experience
F(2, 27) = .155, p =.857, η2 = .011. As a result, it can be concluded that the three
groups (0mg/kg, 1mg/kg, and 3mg/kg) were not signicantly different in terms of
the age, mean ying experience, and mean instrument ying experience.
Design
The experiment was a single blind, between-subjects repeated measures
design. The aim of the experiment was to examine pilots’ performance (psycho-
motor and cognitive performance) in response to low caffeine dosages while
operating a computer based ight simulator. The study comprised one indepen-
dent variable, with three levels (0mg/kg, 1mg/kg, and 3mg/kg of caffeine). The
dependant variables were the horizontal and vertical deviations from the pre-
scribed approach path for runway 34 right into Sydney (Kingsford Smith) Interna-
tional for the baseline and post-treatment ights (see Figure 1).
Effects of Caffeine on Pilot Performance
The International Journal of Applied Aviation Studies
249
Figure 1. Prescribed ILS approach for runway 34R into Sydney International,
Australia (Airservices Australia, 2005).
Participants’ horizontal precession (deviation from localiser) on the instrument
landing system was calculated by analysing ight data obtained by X-planes
data-out feature. Similar to the horizontal precision, vertical precision (deviation
from glide slope) was calculated using absolute numerical values obtained from
the data analysis process. A mean absolute score for each dependent variable
was then calculated, and was said to represent the overall performance of the
pilot.
Apparatus and Stimulus
The material comprised two personal computers, one nineteen inch liquid
crystal display monitor, one ceiling mounted projector, with a Techniques 2 x 2
meter projector screen, and a Personal Computer Aviation Training Device
(PCATD) with Cirrus rudder pedals. The ight simulator software comprised
X-Plane 8.4TM developed by Laminar Research Corporation, while the PCATD
was manufactured by Precision Flight Controls. Other materials comprised of an
information sheet, consent form, demographic questionnaire, personal weight
scales, Zuckerman’s Sensation Seeking scale, Hunter Risk Perception scale 1 and
2, pharmaceutical grade caffeine, and lemon juice.
A ight data recorder, which is a function of the X-Plane software, was used to
record the input from the pilot and the position of the aircraft. Nine specic data
points were saved every one-fth of a second and included: (a) time elapsed, (b)
throttle, (c) pitch, roll, heading, (d) latitude, longitude, altitude, (e) distance trav-
elled (f) height above ground level (g) height above mean sea level, (h) ILS Nav 1
Horizontal deviation, and (i) ILS Nav 1 Vertical deviation. Data obtained relating to
the Horizontal deviation, pilots’ displacement left or right from the runway centre
line was measured in feet, while vertical deviation, pilots’ displacement above and
below the glide path was measured in degrees.
Procedure
Participants were initially weighed and then asked to complete pre-experiment
demographics and consent forms. Those participants who indicated that they did
not abstain from caffeine consumption for a period of 6 hours prior to the experi-
ment as directed, were excluded from the study (2 participants excluded). Partici-
pants were then asked to y two simulated ILS approaches into Sydney Interna-
tional for runway 34R. Each ight took approximately ten minutes to complete.
Between the two ights, and depending on which group participants were assigned,
250
they were asked to consume a lemon based solution containing either, zero, one
or three milligrams of caffeine per kilogram of body weight. Following consump-
tion of the lemon based solution, participants were provided a distracter task that
took approximately 30 minutes and involved completing Zuckerman’s Sensation
Seeking scale and Hunter’s Risk Perception scale 1 and 2. The purpose of the
distracter task was to allow sufcient time for the caffeine administered to be
absorbed. Finally, at the conclusion of the second ight, participants were offered
a glass of water to counter the possible dehydration effect of caffeine, debriefed,
and thanked for their participation.
Results
The main aim of the study was to examine the effect of caffeine at low doses
on pilots’ performance (combination of cognitive and psychomotor). This involved
measuring and comparing deviations, both horizontally and vertically from the
glide path during the two ILS approaches. This was achieved by transferring the
data obtained from X-Plane directly to Statistical Package for the Social Sciences,
version 12.
The effects of prior sleep
Prior to analysing the results of each test ight in relation to the main depen-
dent variable, it was important to establish rst, that the results being examined
were not subject to any external inuences such as the quantity of sleep prior to
the testing phase. Since this has been previously identied as a factor that inu-
ences cognitive performance, all participants were reminded the day prior to the
experiment to maintain as much as possible normal sleeping patterns. Like most
instructions, rules, or regulations, their sheer presence does not guarantee com-
pliance. Therefore, a univariate analysis of variance was employed to determine
whether differences existed between groups based on individual’s response to a
question regarding the quantity of sleep acquired the night prior to testing. The
results revealed a main effect for group (0mg/kg, 1mg/kg & 3mg/kg) F(2, 27) =
6.87, p = .004, η2= .34. A Fisher’s Least Signicant Difference (LSD) post hoc test
revealed that the signicant difference lie between the 1mg/kg group (7.95, SD =
1.46) and the 3mg/kg group (5.80, SD = 2.50) and the 0mg/kg group (8.20, SD =
9.20) and the 3mg/kg group (5.80, SD = 2.50). These results suggest that the
quantity of sleep participants had varied, prior to the experiment, between groups.
Specically, the participants in the 3mg/kg group had, on average less sleep prior
to the study than the participants in either of the placebo or 1mg/kg group. As a
result, sleep was included as a covariate in all analyses.
Horizontal and Vertical Precision
The main aim of the current experiment was to examine the effect of caffeine
on pilot performance, in terms of improvements in deviations both horizontally
and vertically from the glide path. As a result, data obtained from the two ights
(pre/ post) were analysed for the 30 participants using a repeated measures anal-
ysis of variance, with caffeine as the between-subjects factor and sleep as a
covariate. The ANOVA test assumptions were satisfactory. Using an alpha level
Effects of Caffeine on Pilot Performance
The International Journal of Applied Aviation Studies
251
of .05, the results failed to reveal a statistical signicant difference between group
and mean horizontal deviation F(2, 26) = .52, p = .60, η2 = .04; and between group
and mean vertical deviation F(2, 26) = .26, p = .77, η2 = .02. These results suggest
that there were no differences between group and pilot performance. In contrast,
the results revealed a main effect for test session (pre/post) for both horizontal
deviation F(1, 26) = 10.22, p = .004, η2 = .28; and vertical deviation F(1, 26) = 7.89,
p = .009, η
2 = .23. These results suggest a learning effect, where all groups
improved from the rst to the second ight. Finally, the results revealed an interac-
tion between test session (pre/post) and sleep for both horizontal deviation F(1,
26) = 5.64, p = .02, η2 = .18 (see Figure 2); and vertical deviation F(1, 26) = 5.54,
p = .03, η2 = .18 (see Figure 3). In order to determine the precise nature of the
interactions, a series of paired repeated measures analyses were conducted on
each dependent variable with sleep as the covariate. The results revealed one
interaction for horizontal deviation and two interactions for vertical deviation. All
interactions involved the 3mg/kg group. Specically with the horizontal deviation,
the sole interaction was evident between test session (pre/post) and sleep for the
1mg/kg and 3mg/kg group F(1, 17) = 20.89, p = .0001, η2 = .55, while with the
vertical deviation, an interaction was evident between the placebo and 3mg/kg
group F(1, 17) = 4.59, p = .047, η2 = .21 and the 1mg/kg and 3mg/kg group F(1,
17) = 7.45, p = .014, η2 = .31. These results suggest that caffeine had the greatest
effect on those pilots who slept the least in the past 24 hours.
Figure 2. Mean horizontal deviation from flight path between flight one and two
distributed across group.
Figure 3. Mean vertical deviation from flight path between flight one and two
distributed across group.
Deviation from Flight Path - Vertical
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Flight 1 Flight 2
0mg/kg 1mg/kg 3mg/kg
Deviation from Flight Path - Horizontal
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Flight 1 Flight 2
0mg/kg 1mg/kg 3mg/kg
252
Finally, in order to ensure that participant’s performance was not biased by
their ability to operate the simulator, due to the sensitivity of the ight controls, a
univariate analysis of variance was conducted between groups in terms of mean
absolute roll over a 2nm segment of ight, during the initial ight. With alpha set
at .05, the results failed to reveal a statistical signicant difference between group
F(2, 27) =.98, p=.39, η2= .07. This suggests that all group members experienced
a similar level of control sensitivity.
Discussion
The primary aim of the present study was to examine the effects of low dose
caffeine consumption on pilots’ ying performance, under conditions which
reected as much as possible, those normally experienced (30 minutes post
consumption during a crucial phase of ight). Two simulated ights were
undertaken, where in both ights pilots were asked to complete an ILS approach
into Sydney International on runway 34R. Depending on the group assigned, a
placebo, 1mg/kg, or 3mg/kg of caffeine was administered between the two ights
and pilots’ performance, in terms of mean deviation from glide path horizontally
and vertically was compared and analysed. It was hypothesised that caffeine
would have a dose-dependent effect on pilots’ performance.
The results failed to support the hypothesis. An inspection of the results
revealed that irrespective of the group assigned, pilots equally improved from the
rst to the second ight, suggesting a learning effect. This result suggests that
caffeine at low doses, equivalent to 1mg/kg and 3mg/kg has no measurable effect
on pilots’ performance during a simulated ILS approach.
In contrast to the results pertaining to differences between groups, a signicant
interaction was evident between performance (horizontally and vertically) and
sleep. A closer examination of the data revealed that those participants who expe-
rienced the least amount of sleep, and hence improved the most, were overrep-
resented in the 3mg/kg group. Nonetheless, this result suggests that caffeine in
low doses has its most profound effect when pilots are experiencing fatigue or
sleep deprivation.
The results in part, support the anecdotal evidence derived from the aviation
industry relating to the use of caffeine in enhancing pilots’ performance. Specically,
it appears that the benets derived from caffeine in low dosages, relate more to
the cognitive state of the individual, in terms of level of alertness or fatigue
opposed to the quantity of caffeine consumed.
While this result is interesting, and may account in part for the variability in
results from other low dose caffeine studies (see Tucha et al., 2006; Gillingham
et al., 2003), future research needs to investigate the impact of caffeine in low
dosages on fatigued or sleep-deprived individuals to accurately determine its full
effect.
Similarly, the converse of this may also be true, in that caffeine in low dosages
may only noticeable enhance performance in well-rested individuals when
Effects of Caffeine on Pilot Performance
The International Journal of Applied Aviation Studies
253
engaged in a task that is considered highly cognitively demanding. While Snel,
Lorist, and Tieges, (2004) and Tucha et al., (2006) have found evidence of this with
caffeine in moderate dosages, there appears to be limited research examining its
effect in dosages more akin to the present research. As a result, future research
should examine the effects of caffeine at low dosages, with well-rested individuals
on tasks which are considered highly demanding.
Limitations
The results of this study should be interpreted with the presence of certain
limitations. Specically, in the present study it was assumed that a direct relation-
ship existed between quantity of sleep and cognitive preparedness. While evi-
dence in support of this can be derived from Kohler et al., (2006) Kamimori et al.,
(2005) and Lieberman et al., (2002) future research should consider employing an
objective measure to determine this relationship. Similarly, it would also be prudent
to investigate the effects of low dose caffeine on fatigue opposed to sleepiness in
isolation, as research has indicated that both the effects and countermeasures for
these two conditions are very different (Philip et al., 2005). Finally, and while there
is no evidence to suggest that the nature of the experimental design (single-blind)
adversely impacted on the research, future research should nonetheless consider
employing a double-blind experimental design to reduce the potential of any
researcher bias.
Conclusion
In summary, caffeine has been cited as a coping mechanism to help manage
fatigue and improve performance (Fredholm et al., 1999). On the ight deck,
caffeine is employed to alleviate some of the symptoms associated with sleep loss,
fatigue, a busy work schedule, or just to improve pilot performance (Petrie, &
Dawson, 1997; Caldwell, 1997). The results of the present study suggest that
caffeine in low dosages only appears to be an effective mechanism to achieve
these performance enhancements when pilots are fatigued from lack of sleep.
While the results positively reect the short-term benets of caffeine in low dosages
with sleep deprived individuals, from an operational perspective, alternates such
as increasing sleep time and reducing exertion prior to duty, planning energy
expenditure, and employing active coping strategies while on duty, as prescribed
by Petrie and Dawson, (1997) and Petrie, Powell, and Broadbent, (2004) may be
more effective performance enhances than relying on caffeine alone in the long-
term.
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