Protocol Summary. The investigators will collect objective and subjective sleep, sleepiness,
workload, and performance data from on-duty pilots during the aforementioned short-haul
flight operations. Data will be collected during days off prior to the trip start, during
flights, and during days off following the flight operations. Each participant will collect
data during two trips lasting 2-7 days each, with up to 3 days of off-duty data collection
before and after each trip, for a total data collection of up to 26 days per pilot.
Study Aims. The goal of this study is to provide insight into the influence of trips
including circadian disruption on pilot cognitive performance, fatigue, sleepiness, sleep,
and workload during short-haul operations across multiple airlines.
Hypothesis. Cognitive performance, fatigue, sleepiness, and sleep outcomes will be worse
during circadian disrupted trips compared to trips that do not involve circadian disruption.
Statistical Analyses. The following factors will be also considered for inclusion in the
analysis:
Schedule features: flight duration, duty duration, duty start and finish times
Individual factors: age, experience, chronotype (as measured by the
morningness-eveningness questionnaire), sleep need
Sleep: sleep duration, sleep loss, sleep start and finish times (all measured by the
actiwatch)
Fatigue/alertness: pre- and post-sleep and on-duty fatigue and alertness ratings (as
measured by subjective scales)
Workload: hassle factors encountered during flights and NASA TLX
Procedure Pre-study Questionnaires. Once consented, participants will complete a series of
baseline questionnaires including a demographic questionnaire, performance questionnaires, a
baseline exercise questionnaire, the Morningness/Eveningness Questionnaire (MEQ), the Epworth
Sleepiness Scale (ESS), the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity
Index (ISI), and the NASA Task Load Index (TLX), using the NASA PVT+ app. Participants will
also complete a practice sleep diary and a practice PVT in order to ensure that they
understand the study procedures. Demographic information, including age, flight experience,
living arrangements, and the results of the aforementioned questionnaires will be used as
covariates in data analysis as each of these factors can influence sleep and performance.
Participants will begin data collection 1-3 days prior to their trip departure (depending on
the participant's availability and off-duty time between trips). Data will be collected using
the NASA PVT+ App and the Actiwatch. Participants will begin wearing the Actiwatch and
continue to wear it for the duration of the study period which will conclude up to 3 days
following their return from their trip. Participants will make entries in the App reporting
on their sleep periods at the beginning and end of each day, including days off. Participants
will also have additional entries during flight duty periods. Entire study period can last up
to 26 days depending on length of trips and days off in between.
Morning Sleep Diary. At the beginning of each day, participants will complete a sleep diary
within the NASA PVT+ App. Each entry will include: wake-up time, a rating of sleep quality (5
-point scale from Extremely Good to Extremely Poor), the Samn-Perelli (SP) and Karolinska
Sleepiness Scale (KSS), the location of their sleep, the timing and duration of any
awakenings during the sleep period, and any additional information (i.e., notes).
Evening Sleep Diary. At the end of each day (right before sleep), participants will use the
App to report the time they are going to sleep, the location of their sleep (e.g., home,
hotel), if they used any caffeine during the day (amount used), any naps during the day
(including timing and duration), timing/type of meals, and timing/type of exercise.
Participants will also complete the SP and KSS and have an opportunity to provide any
additional information about the day if necessary.
Flight Duty Period Data Collection. On flight duty days, participants will have additional
entries and tasks to complete within the NASA PVT+ App (i.e., pre-duty, during flight,
post-flight, and post-duty). Pre-duty entries will include: flight information, layover
information, commute information, caffeine intake, the SP and KSS, and the Psychomotor
Vigilance Task (PVT). During their flight, Participants will complete the SP, KSS, and the
PVT, at or near the timing of TOD. Post-flight entries will occur within one hour of landing
and will include flight information, the NASA TLX, report of fatigue countermeasures used,
and hassle factors experienced (e.g., weather, air traffic control issues, traffic), SP, KSS,
and PVT (if needed). Post-duty entries will include: duty information, operational factors
(e.g., delays, sit times), overall fatigue rating (visual analog scale), KSS, SP, and PVT.
Participants will also complete both the morning and evening sleep diary entries on flight
duty days. Additional questions in the evening sleep diary on duty days include: commute
information (i.e., timing, duration, and type of travel).
Participant Withdrawal. Participants who choose to withdraw their consent may do so at any
time. Any partial data that has been collected will be considered for analysis unless the
participant requests that their data be deleted.
Tests and Scales Morningness/Eveningness Questionnaire (MEQ). The MEQ is a widely used
self-assessment questionnaire (19 items) designed to determine a person's chronotype, that
is, whether they experience peak alertness in the morning, evening, or in between.
Pittsburgh Sleep Quality Index (PSQI). The PSQI is used to measure sleep quality in adults
over the last month. The scale is broken down into 7 Components, which include: subjective
sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances,
use of sleeping medications, and daytime dysfunction. Higher scores indicate poorer sleep
quality.
Insomnia Severity Index (ISI). The ISI is a 7-item questionnaire used to assess the severity
of daytime and nighttime components of insomnia. The scale uses a 5-point Likert scale to
measure the different components, including: severity sleep onset, sleep maintenance, early
morning awakening problems, sleep dissatisfaction, interference of sleep difficulties with
daytime function, noticeability of sleep problems by others, and distress caused by the sleep
difficulties. Total score can range from 0-28 with higher scores indicating more severe
insomnia.
Epworth Sleepiness Scale (ESS). The ESS is a routinely used self-administered questionnaire
(8 items) that can be used to assess daytime sleepiness.
NASA-TLX. The NASA Task Load Index (TLX) is a subjective, multidimensional tool that rates
workload relative to a task. The TLX is taken at the start of the study to make a series of
pairwise comparisons and then again for rating each flight period.
Hassle Factors. Factors that may affect workload during flight operations (e.g., weather, air
traffic control (ATC), cabin activity, procedures & documentation) will be reported for each
flight period.
Samn-Perelli Scale (SP). The Samn-Perelli Scale is a commonly used 7-point scale for
self-rating levels of fatigue at a given time. The scale includes: 1= fully alert - wide
awake, 2= very lively, 3= okay - somewhat fresh, 4= a little tired, 5= moderately tired, 6=
extremely tired, 7= completely exhausted.
Karolinska Sleepiness Scale (KSS). The KSS is a widely used 9-point scale for self-rating
levels of sleepiness at a given time. The scale includes: 1 = extremely alert, 2= very alert,
3 = alert, 4= rather alert, 5 = neither alert nor sleepy, 6= some signs of sleepiness, 7 =
sleepy - but no difficulty remaining awake, 8= sleepy - some effort to keep awake, and 9 =
extremely sleepy - fighting sleep.
Sleep Quality rating. All sleep periods (including naps) will be rated for quality. The scale
includes: 1 = extremely good, 2= good, 3 = average, 4= poor, 5 = extremely poor.
Psychomotor vigilance task (PVT). The PVT is a widely used sustained-attention, reaction-time
task that measures the speed with which subjects respond to a visual stimulus. The PVT is a
simple task where the subject taps the screen as soon as a visual stimulus appears. The
stimulus appears randomly every few seconds during the 5-minute task.
Equipment The study will involve evaluating pilot sleep, sleepiness, performance, and
workload among on-duty pilots. All devices are commercial, off-the-shelf products with no
modifications and used as directed.
iPod. Participants will be issued an iPod Touch with a pre-loaded application (NASA PVT+)
which includes a sleep diary, cognitive tests, and subjective scales (Figure 1). Using the
NASA PVT+ App, measures will include PVT speed (1/reaction time) and lapses conducted at
pre-flight, top of descent (TOD), post-flight, and on days off. Subjective fatigue ratings
using the Samn-Perelli 7-point scale and sleepiness ratings using the 9-point Karolinska
Sleepiness Scale at pre-flight, TOD, post-flight, and on days off will also be reported. At
the end of each flight, participants will complete the NASA-TLX, hassle factors, and
information about any fatigue countermeasures that they used. Participants will also capture
information about the characteristics of the flight at the end of each Flight Duty Period
(FDP). Prior to and at the end of the study, the participants will use the app to complete
baseline questionnaires.
Actigraphy. Participants will wear a small wristwatch-like device (Actiwatch, Philips
Respironics, Murrysville, PA, USA) on the wrist of their non-dominant arm (Figure 2). The
actiwatch will be worn continuously throughout the study period including on days off.
Actigraphy uses accelerometry and a light sensor to determine sleep and wake patterns and may
be worn for several weeks at a time. It will provide us with objective sleep measures which
can be compared and correlated with other measures recorded in the NASA PVT+ App.
Light and Temperature Sensor. Participants will wear a small (~1 square inch) light sensor
clipped to their clothing in order to assess their lighting and ambient temperature exposure.
This device can be placed on a bedside table during sleep. It can record light information
for several weeks and does not require the user to interact with it in any way. The data
obtained from this sensor will allow us to use the participant's pattern of light exposure to
estimate circadian phase using a biomathematical model.
