Fatigue in Long-Haul Operations

This study will evaluate whether a calorie restriction and lighting countermeasure are capable of improving performance and reducing fatigue and sleepiness among commercial airline pilots during trips that involve long-haul (LH) overnight operations. All participants will collect data for two LH trips that involve overnight flying, and for three days before and after each trip. All participants will collect baseline data for one trip with no intervention. Upon completion of the baseline trip, participants will be randomized to receive the intervention or control for a future similar trip. The intervention will involve asking pilots to reduce their calorie intake during the biological night to < 10% of their daily need and to wear blue-enriched light emitting glasses for 20 minutes following their inflight rest break before they return to the flight deck. The control condition will involve reminding pilots about standard fatigue risk management practices that are recommended by their company.

Specific Aims: The aim of this study is to determine whether a calorie restriction and lighting intervention will improve alertness and performance during LH flight operations compared to standard fatigue risk management practices among pilots flying LH overnight operations during outbound and return flights.

Hypotheses:

We hypothesize that:

1. pilot alertness, fatigue, mood, and performance at top of descent (TOD) will be better among pilots randomized to limit their overnight calorie intake to a small snack (<10% daily calorie needs) compared to those who are not provided with guidance on calorie restriction.
2. pilot alertness, fatigue, mood, and performance following their inflight rest break will be better following exposure to blue-enriched lighting compared to no blue-enriched lighting.

Primary Outcome Measures:

We will measure self-reported sleepiness using the Karolinska Sleepiness Scale (KSS), which is a 9-item Likert scale that is used to assess sleepiness. We will measure self-reported fatigue using the Samn-Perelli scale (SP), which is a 7-item Likert scale that is used to assess fatigue. We will measure mood using a series of visual analog scales (VAS). We will measure objective cognitive performance using the five-minute psychomotor vigilance task (PVT), a simple reaction time task with outcome measures including mean reaction time, response speed (1/reaction time) and number of lapses (reaction time >500ms). These outcomes will be assessed throughout the study, with primary comparisons between conditions evaluated ~20 minutes after waking from inflight rest and at the top of TOD of each flight.

We will also collect a number of secondary outcomes to use as co-variates in analysis and to conduct exploratory analyses. These include measures taken three days before and after each trip, during layover, and also at the top of climb (TOC) for each flight. The specific measures that we will collect are outlined below and include objective and subjective sleep outcomes, exercise information, food intake timing and composition, hunger, workload, and perceived performance. We will also collect a number of baseline questionnaires to document demographics and typical sleep and eating habits.

Participants will begin data collection 3 days prior to their trip departure. At the start of data collection (for each trip), participants will begin wearing the activity monitor and continuous glucose monitor and continue to wear them for the duration of the study period which will conclude 3 days following their return from their trip. They will make entries in the apps, reporting on their sleep periods, food intake, and exercise each day. Participants will collect additional data on duty characteristics (hassle factors like delays, air traffic control issues, countermeasures employed, hotel issues, etc.) during the trip. Participants will be asked to complete a follow-up survey/debrief about their experience 1-3 months following their participation.

Measures Morning Sleep Log. At the beginning of each day, participants will complete a sleep log 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). Pre- and post-flight naps will be logged separately.

Evening Sleep Log. At the end of each day (right before sleep), participants will use the NASA PVT+ app to log the time they are going to sleep and any naps taken since the last sleep entry (including timing and duration). Participants will also complete the SP and KSS and have an opportunity to provide any additional comments 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, the SP, KSS, mood ratings, and the PVT.
• During flight, they will complete the SP, KSS, mood ratings, and the PVT, at or near the timing of TOC and TOD, and before and after inflight rest. In addition, participants will complete TLX at or near time of TOC and TOD, and sleep log after inflight rest.
• Post-flight/duty 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, mood ratings and PVT (if needed).
• Participants will also complete both the morning and evening sleep log entries on flight duty days. Additional questions in the sleep log on duty days include: commute information (i.e., timing, duration, and type of travel) and any hotel-related disruptions.
• Participants will be told to not complete study tasks if they would interfere with flight duties and that study tasks may be delayed, skipped, or stopped without penalty whenever operationally unsafe or impractical. If the data collection is too disruptive, participants may discontinue participation in the study.

Food and fluid intake. Participants will document their food and fluid intake throughout the entire data collection period using the LoseIt! application. The LoseIt! app will be set up by the study team so that it does not include any personally identifiable information (i.e., a code will be used instead of the participant's name). Participants will be instructed to document their food and fluid intake as they consume it. The data will be checked by study staff each day to ensure the participant completed data input.

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. The MEQ will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

Epworth Sleepiness Scale (ESS). The ESS routinely used self-administered questionnaire (8 items) that can be used to assess daytime sleepiness. The ESS will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

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. The ISI will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

Pittsburgh Sleep Quality Index (PSQI). The PSQI is a 19-item questionnaire that quantifies sleep quality, latency, and duration, and daytime dysfunction into a single score that distinguishes good from poor sleepers. The PSQI will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

The Big Five Personality Inventory - 2 (BFI-2). The BFI-2 is an updated version of the BFI-1 with further breakdowns (i.e., "facets") of each of the 5 dimensions/trait: Extraversion (with facets of Sociability, Assertiveness, and Energy Level), Agreeableness (Compassion, Respectfulness, and Trust), Conscientiousness (Organization, Productiveness, and Responsibility), Negative Emotionality (Anxiety, Depression, and Emotional Volatility), and Open-Mindedness (Intellectual Curiosity, Aesthetic Sensitivity, and Creative Imagination). The original BFI-2 is 60 items. The BFI-2 will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

The Chrononutrition Questionnaire (CP-Q). The CP-Q is an 18-item questionnaire that assess general patterns of chrononutrition preferences and chrononutrition behaviors, on typical work/school days and free days. The CP-Q will be administered at the beginning of the study as part of the baseline demographic series of questionnaires.

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 duty period.

Hassle Factors. Factors that may affect workload during flight operations (e.g., weather, ATC, cabin activity, procedures \& documentation) will be reported for the flight duty period. Hassle Factors are collected in post-flight using the NASA PVT+ App.

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: 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: 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: 1 = extremely good, 2= good, 3 = average, 4= poor, 5 = extremely poor.

Visual analog scales (VAS) of mood. A series of 100-point bi-anchored mood scales including the following pairs: alert-sleepy, cheerful-miserable, calm-tense, depressed-elated, stressed-relaxed, peaceful-hostile, greedy-generous, aggressive-easygoing, lethargic-energetic. Participants mark on the horizontal line to indicate how they are currently feeling. The VAS will be administered in conjunction with the PVT, KSS, and SP.

Self-Reported Performance Rating. Participants will be asked to rate how well they thought they performed after each test bout on a 7-point scale ranging from "extremely good" to "extremely poor". The scale will be administered before and after each PVT.

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.