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The effects of low dose caffeine on pilot performance


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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' performance 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 instrument 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 significant. 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 performance are reviewed. Recommendations are made for future studies in this field.
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The International Journal of Applied Aviation Studies 244
The Effects of Low Dose Caffeine on Pilot Performance
Tom J. Caska
Brett RC. Molesworth
University of New South Wales
Department of Aviation
UNSW Sydney NSW 2052
+61 2 9385 6757 (Telephone)
+61 2 9385 6637 (Facsimile)
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
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 efciency (Caldwell, 1997). This scenario can be
further intensied 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 specically 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
signicantly 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.
Caffeine per
serve (mg)
Equivalent servings for an 176lb/80kg person
Experimental Groups
0 mg/kg 1 mg/kg 3 mg/kg
Brewed 200 0 0.4 1.2
Instant 30-120 0 2.6 - 0.6 8.0 - 2.0
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. Specically, while Smit and Rogers (2000) found that as
little as 12.5mg of caffeine can signicantly 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 signicantly 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 benecial effects of caffeine in a dose-dependent manner (Lieberman,
Tharion, Skukitt-Hale, Speckman, & Tulley, 2002; Kamimore, Johnson, Thorne, &
Belenky, 2005; McLellan et al., 2004). Specically, 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
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 reected 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 reective of
this environment (between 20 and 30 minutes from touchdown). Since caffeine
withdrawal has also been identied 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 inuenced participants, resulting in a ‘placebo
effect’. Nevertheless, the researchers viewed the potential risk of this occurring to
be signicantly 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.
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 Certicate, 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 signicant 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 signicantly different in terms of
the age, mean ying experience, and mean instrument ying experience.
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
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
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 specic 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.
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,
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 sufcient 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.
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 inuences such as the quantity of sleep prior to
the testing phase. Since this has been previously identied as a factor that inu-
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 Signicant Difference (LSD) post hoc test
revealed that the signicant 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.
Specically, 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
of .05, the results failed to reveal a statistical signicant 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. Specically 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
Flight 1 Flight 2
0mg/kg 1mg/kg 3mg/kg
Deviation from Flight Path - Horizontal
Flight 1 Flight 2
0mg/kg 1mg/kg 3mg/kg
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 signicant difference between group
F(2, 27) =.98, p=.39, η2= .07. This suggests that all group members experienced
a similar level of control sensitivity.
The primary aim of the present study was to examine the effects of low dose
caffeine consumption on pilots’ ying performance, under conditions which
reected 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 signicant
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. Specically,
it appears that the benets 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
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
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.
The results of this study should be interpreted with the presence of certain
limitations. Specically, 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.
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 reect the short-term benets 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-
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... These interventions studied the effects of caffeine [28,39], fluid [40], fiber [4], and macronutrients [41]. Four studies used computer simulations [38][39][40][41], and one used a simulated flight altitude [4]. The length of flight simulations was reported in all studies and ranged from 10 min to 8 h. ...
... All studies were RCTs. The interventions were administered in food form [4,41], liquid form [38,40], or as a tablet/pill [39]. Two studies reported performing a power calculation to determine sample size [40,41]. ...
... The results were collected for all participants immediately following the flight simulation. Full compliance with procedures (100%) was reported in three interventions [4,38,39]. ...
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Airline passengers experience a range of symptoms when travelling on long flights. This review evaluated the efficacy of functional foods, beverages, and supplements claiming to address the effects of air travel for healthy adults. Products were identified in a scoping review of electronic databases, search engines, and grey literature (March to August 2019). A systematic review of the efficacy of product ingredients was conducted using five electronic databases from inception to February 2021. Articles were screened, data extracted, and assessed for risk of bias by two researchers independently. Meta-analysis was performed. Of the 3842 studies identified, 23 met selection criteria: melatonin (n = 10), Pycnogenol (n = 4), various macronutrients (n = 2), caffeine (n = 2), Centella asiatica (n = 1), elderberry (n = 1), Echinacea (n = 1), fluid (n = 1), and Pinokinase (n = 1). Meta-analysis (random effects model) indicated melatonin reduced self-reported jetlag following eastbound (n = 5) and westbound (n = 4) flights: standard mean difference −0.76 (95% CI = −1.06 to −0.45, I2 0%, p < 0.00001) and −0.66 (95% CI = −1.07 to −0.26, I2 45%, p = 0.001), respectively. Pycnogenol also reduced edema scores (n = 3), standard mean −4.09 (95% CI = −6.44 to −1.74), I2 98%, p = 0.0006). Overall, 12 of 183 ingredients contained in 199 products had evidence to support claims.
... However, it is present in a large (but not all) number of other consumable products such as chocolate, candy, medication, and some energy drinks (Daly, 1993). The benefits of consuming caffeine include: reducing the effects of fatigue (Petrie & Dawson, 1997;Caska & Molesworth, 2007), improving alertness (Caldwell, 1997), enhancing vigilance (Smith, Kendrick, Maben, & Salmon, 1994), enhancing physical performance (Wiles, Colemand, Tegerdine, & Swaine, 2006) and improving decisionmaking (Lyvers, Brooks, & Matica, 2004). ...
... In everyday life outside of flying, pilots and other professionals alike rely on caffeine for the same Ricky Young and Brett R. C. Molesworth Castellano, 1996;Si, Zhang, & Maleszka, 2005;Caska & Molesworth, 2007). ...
... Specifically, pilots and other professionals alike consume caffeine in the form of coffee or tea in dosages equivalent to three milligrams per kilogram of body weight. This roughly equates into one large strong cup of coffee, or two averagesized cups, opposed to a five milligram per kilogram dose (see Caska & Molesworth, 2007). Finally, pilots were selected for the research namely because: they self-report high levels of caffeine consumption directly prior to crucial phases of flight, such as landing (Petrie & Dawson, 1997;Taneja, 2007), and the hierarchical structure on most flight decks reflects that of a trainer-trainee performance enhancing properties. ...
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Caffeine is known for its performance enhancing properties. The majority of research focuses on the immediacy effect of caffeine on performance. In contrast, there appears to be limited understanding of the effect of caffeine on the rate at which individuals acquire or learn information. As a result, the present study sought to investigate whether caffeine can facilitate the rate at which individuals acquire and apply skills. Forty-five participants (all pilots) were randomly divided into three groups (0mg/kg, 3mg/kg & 5mg/kg of caffeine) and were asked to complete twelve sessions on a complex computer-based game titled Space Fortress. Following two familiarization trials, administration of caffeine, and a 30-minute distracter task, all participants completed ten consecutive sessions on Space Fortress. Data relating to individual performance on the ten sessions were analyzed in four separate areas - Total Score, Control, Speed, and Accuracy. The results revealed a trend where the 3mg/kg group outperformed both the 0mg/kg and the 5mg/kg groups. The results also suggest that caffeine in dosages equivalent to 5mg/kg have the potential to hinder effective learning. These findings are discussed from a theoretical and operational perspective.
... This study extends the research conducted by Caska and Molesworth (2007) who found that caffeine in low (1mg/kg) and moderate (3mg/kg) dosages failed to improve pilots' performance during a simulated instrument landing system approach into Sydney International airport. The study was designed to reflect as much as possible the operational conditions typically encountered by commercial aviation pilots. ...
... The primary aim of the present study was to extend the research conducted by Caska and Molesworth (2007) and examine the effects of caffeine in both moderate and high dosages on pilot performance. Caska and Molesworth found that caffeine in low (1mg/kg) and moderate (3kg/kg) dosages failed to improve pilots' ability to fly an instrument landing approach into Sydney International Airport on a computerbased flight simulator. ...
Fatigue relating from sleep loss or circadian disruptions continues to pose a significant threat within aviation. Caffeine is one method employed by pilots on the flight deck to alleviate some of the symptoms associated with fatigue. The present study sought to investigate the effects of caffeine on pilot performance during a demanding task. Employing a repeated measures design, forty-two pilots were randomly divided into three groups (Omg/kg, 3mg/kg and 5mg/kg of caffeine) and completed a base-line task followed by a test task, thirty minutes post caffeine consumption. Both experimental tasks involved pilots completing games on Space Fortress - a computer-based research tool developed at the University of Illinois - Cognitive Psychophysiology Laboratory for the study of complex skills. The results failed to reveal any difference in pilots' performance from the consumption of caffeine. The results are discussed from both an applied and experimental perspective.
... Ingestion of low-to-moderate (~40-300 mg) doses of caffeine can improve alertness, vigilance, reaction time, and measures of attention, particularly when sleep deprived (McLellan et al., 2016). Some studies have also found a benefit on flight performance during sustained wakefulness (Caska & Molesworth, 2007;Doan et al., 2006), though others have not (Kilpeläinen et al., 2010;Lohi et al., 2007). These mixed results could be related to several factors, including differences in study methodology and interindividual differences in caffeine responses (Yang et al., 2010). ...
Objective: To synthesize the observational data on stimulant use in civilian and military aviation. Background: Pilot fatigue is a major safety concern and effective countermeasures are crucial for sustaining flight performance. Stimulants are not recommended for routine use but can help sustain alertness and flight performance when the risk of fatigue is high. However, they may also elicit side effects. It is important to fully understand the contexts in which stimulants are used, including factors that contribute to their use and how aviators perceive them. Methods: A systematic literature search was conducted to identify observational studies on stimulant use specific to aviation tasks. Results: Caffeine was frequently used in civilian aviation, though prevalence of use and perceptions about efficacy depend on task demands and individual caffeine responses. Stimulant use in military aviation was dependent on several operational factors, including the duration and timing of operations, recent hypnotic medication use, and whether other fatigue countermeasures could be utilized. Military aviators generally viewed stimulants as beneficial and side effects were sparse and mild-moderate with a few exceptions. Notably, most studies identified were published over 10 years ago. Conclusion: Stimulant use is relatively common in aviation and many (but not all) aviators perceive them as beneficial, though more studies should be conducted in the modern aviation environment. Major side effects were rare, with a few exceptions.
General aviation is the most diverse sector in all of aviation, encompassing everything outside of military and airline flying. From its great diversity arises a similar variety of safety challenges. This chapter surveys what we have learned about the human factors of staying safe while we teach and train, conduct business in the sky, and when we fly for fun. Some human factors research will confirm ideas that you have long held—while other fascinating studies will invite you to think about old topics in new ways.
INTRODUCTION: Fatigue is a common problem in aviation. The identification of efficacious fatigue countermeasures is crucial for sustaining flight performance during fatigue-inducing operations. Stimulants are not recommended for consistent use, but are often implemented during flight operations with a high risk of fatigue. As such, it is important to evaluate the efficacy of approved stimulants for sustaining flight performance, alertness, and mood. METHODS: Four electronic databases (PubMed, PsycInfo, SPORTDiscus, Web of Science) were systematically searched to identify research on the effects of caffeine, dextroamphetamine, and modafinil during simulated or in-flight operations. RESULTS: There were 12 studies identified that assessed the effects of at least 1 stimulant. Overall, dextroamphetamine and modafinil were effective for sustaining flight performance and pilot mood during extended wakefulness. Results with caffeine were inconsistent. DISCUSSION: Dextroamphetamine and modafinil appear to sustain flight performance and mood during extended wakefulness. However, most studies have used flight simulators and short operation durations. Additional research is needed in realistic settings and during longer duration operations. Caffeines effects were inconsistent across studies, possibly due to differences in study methodology or individual caffeine responses. Despite fatigue being a common problem in civilian aviation as well, only one study in this review included civil aviators. More research should be conducted on the effects of caffeine during civil operations. CONCLUSION: Dextroamphetamine and modafinil appear to be effective fatigue countermeasures but should be further evaluated in more ecologically valid settings. The effects of caffeine are unclear at this time and should continue to be evaluated. Ehlert AM, Wilson PB. Stimulant use as a fatigue countermeasure in aviation . Aerosp Med Hum Perform. 2021; 92(3):190200.
The aim of this research was to examine the relationship between cue utilization, spatial aptitude and skill acquisition in learning to fly a simulated small Visual Line-Of-Sight (VLOS) rotary-wing Remotely Piloted Aircraft (RPA) or Unmanned Aerial Vehicle (UAV). The participants were 95 university students with no prior RPA or conventional aviation experience. Participants completed the EXPERT Intensive Skills Evaluation (EXPERTise) 2.0 web-delivered cue-based Situational Judgement Test (SJT) to ascertain their level of cue utilization and a series of spatial aptitude batteries. The participants then completed two 15 min simulated small VLOS rotary-wing RPA piloting tasks. A performance score, based on the proportion of successful trials, comprised the dependent variable for task one and a composite performance score, based on the proportion of successful trials, progression through the obstacle course, and time to complete a course, comprised the dependent variable for task two. The results indicated that, during the initial task, performance was explained by total video game experience and levels of spatial visualisation, while performance during the second task was explained by levels of cue utilization. This outcome suggests the involvement of different cognitive constructs at different stages in the initial and immediately subsequent stages of unstructured learning to operate a simulated VLOS rotary-wing RPA. The results suggest that the small VLOS remote pilot training industry might benefit from the development of cue-based training packages that assist trainees acquire interpret, integrate, calibrate and adapt the right sorts of cues that facilitate or accelerate the acquisition of competence and ultimately the progression to expertise.
It is often said that there are three classes of aviation: military, airlines, and everybody else. Everybody else is better known as general aviation, and on any given flying day, it might include flight training, pleasure flying, police and sheriff air patrol, aerial firefighting, aerial burial, crop dusting, and so on. General aviation accounts for roughly 87% of the almost 600,000 U.S. certificated pilots, and makes use of more than 13,000 public and private airports. General aviation pilots vary widely in their experience: from highly experienced corporate pilots to new student pilots who excitedly log their first minutes of flight time. General aviation aircraft can range from the most primitive amateur-built craft, to the highest-tech glass cockpit jets, to the futuristic folding-wing airplane that can be driven home after landing. General aviation accidents occur at a rate of roughly 6 accidents per 100,000 flight hours, while accidents involving fatalities occur at slightly more than 1 per 100,000 hours. Although these numbers show a continuing overall trend toward improvement, general aviation remains the riskiest of the three classes of aviation. It comes as no surprise that safety remains a top concern for human factors professionals who work in the aviation field. This chapter looks at the human factors issues that impact safety in the three largest sectors within general aviation: (1) personal flying, (2) flight training, and (3) business flying.
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Two experiments examined the effect of breakfast (1.89 MJ) and caffeine (4 mg/kg) on cognitive performance, mood and cardiovascular functioning. In the first experiment, breakfast had no effect on performance of sustained attention tasks, but it increased pulse rate and influenced mood. The mood effects after breakfast differed between a cooked breakfast and a cereal/toast breakfast. In contrast to the effects of breakfast, this relatively high dose of caffeine improved performance of the sustained attention tasks, increased blood pressure and increased mental alertness. In the second experiment, effects of a breakfast and caffeine on mood and cardiovascular functions confirmed the results of the first study. The breakfast improved performance on free recall and recognition memory tasks, had no effect on a semantic memory task and impaired the accuracy of performing a logical reasoning task. In contrast to this, caffeine improved performance on the semantic memory, logical reasoning, free recall and recognition memory tasks. Overall, these results show that breakfast can improve performance in some but not all cognitive tasks and that these changes are very different from those observed after lunch, and those produced by caffeine.
This book illustrates how food and the act of eating touches the everyday lives of individuals, including nearly every aspect of human behaviour and development. It assists in recognizing the associations that current scientific evidence concerning nutrition and behaviour suggests are likely true, given the current understanding of work that bridges the two topics. Particular topics discussed include: concepts and models in nutrition and behaviour; research and analytical methods; direct and short-term effects of nutrition on behaviour (brain-behaviour connections and neurotransmitters); effects of chronic and acute undernutrition; the effect of vitamins, minerals and dietary supplements on mental performance and behaviour; bio-behavioural and psychosocial influences on nutrition; dietary sugar and behaviour; caffeine, the methylxanthines and behaviour; alcohol and brain function; eating disorder syndromes; and behavioural aspects of overweight and obesity.
Similarities in beverage preparation procedures, their twin roles as caffeinated stimulants, and wide familiarity with coffee and tea, encourage the common misconception that their technology and chemistry are similar. One (coffee) originates from a pyrolized seed, the other (tea) from a fermented leaf. Other differences include processing temperature, the nature of their oxidation, and the timing and control of enzymatic activity. Flavor development in coffee results from high temperature degradation of carbohydrate, protein, and lipid materials while in tea it stems mainly from oxidation of polyphenols. Differences in amounts of caffeine in the beverage result from differences in raw product processing and variations in beverage preparation practices.
Fatigue is a major problem for international aircrew flying transmeridian routes. One hundred eighty-eight international pilots responded to a questionnaire that assessed overall fatigue and the symptoms pilots associated with fatigue on duty. The questionnaire also assessed the methods used by pilots to cope with fatigue before a duty as well as on the flight deck. Analysis showed that these symptoms could he grouped into five factors: sleepiness, cognitive dysfunction, emotional disturbance, boredom, and physical effects. Pilots reporting high levels of overall fatigue differed from other pilots in terms of noticing symptoms related to cognitive difficulties and emotional disturbance. The most common coping strategies used prior to a duty involved napping and conserving energy. Coping strategies used by pilots on the flight deck could be grouped into five factors: planning energy use, active coping, mental withdrawal, communicating with other crew, and coffee drinking. In their coping strategies during flights, high-fatigue pilots differed from other crew in their higher use of energy planning. The study suggests that pilots reporting high levels of fatigue may use different sensations to monitor when they are tired. Modifying some of the less functional coping strategies used by high-fatigue pilots may he a useful point of intervention to reduce fatigue.
Caffeine effects on arousal and cognition were assessed in relation to habitual caffeine intake. After drinking either decaffeinated coffee or decaffeinated coffee plus 300 mg caffeine, 22 heavy caffeine consumers (HCCs) and 26 light caffeine consumers (LCCs) were examined on various cognitive, autonomic, and anxiety measures. In LCCs only, caffeine significantly improved performance of the Wisconsin Card Sorting Test, and significantly increased state anxiety scores. Caffeine significantly increased spontaneous skin conductance responses in HCCs and LCCs alike. The HCCs and LCCs did not differ on measures of trait anxiety or neuroticism. Results are discussed in terms of the cognitive enhancing and nonspecific arousing effects of caffeine in relation to caffeine tolerance.
The role of human error in commercial and general aviation accidents and the techniques used to evaluate it are reviewed from a human-factors perspective. Topics addressed include the general decline in accidents per million departures since the 1960s, the increase in the proportion of accidents due to human error, methods for studying error, theoretical error models, and the design of error-resistant systems. Consideration is given to information acquisition and processing errors, visually guided flight, disorientation, instrument-assisted guidance, communication errors, decision errors, debiasing, and action errors.
Caffeine is thought to have stimulant-like behavioral effects on mood and performance. However few behavioral studies have examined this substance's acute effects when administered in a range of doses that include the low doses typically found in foods and over-the-counter drugs. We therefore gave single doses of caffeine (32, 64, 128 and 256 mg) to 20 healthy male subjects and assessed various aspects of performance and self-reported mood states, as well as plasma caffeine concentration. As little as 32 mg (which elevated plasma caffeine concentration to less than 1 microgram/ml), typical of the dose found in a single serving of a cola beverage, and less than that found in a single cup of coffee or a single dose of over-the-counter drugs, significantly improved auditory vigilance and visual reaction time. All other caffeine doses administered also significantly improved performance on these tests. No adverse behavioral effects, such as increased anxiety or impaired motor performance, were noted even at the highest dose administered.