Note: The current study is no longer recruiting.

What is the purpose of the study?
We are investigating factors that influence sleep and comfort in the business class cabin environment.

Who can take part in the study?
Inclusion criteria:
• Age range: 21 years old and above, or NUS students 18 years old and above
• General good health (no sleep disorders or chronic diseases)

Exclusion criteria:
• Any acute, chronic or debilitating illness or injury at the time of recruitment
• Currently taking medications or other substances that may affect sleep
• Recent history of smoking or other substance use or dependency
• History of contact dermatitis
• Habitual sleep duration < 6 hours per night or very poor sleep quality (PSQI >10)
• Extreme chronotype (assessed using the Horne-Ostberg morningness-eveningness questionnaire (MEQ) – score < 31 or > 69)
• Shift work or travel across time zones during the study period
• Failure to keep to sleep-wake schedule
• Not agreeable to audio- and video- recording of the session

How long is the study?
The research study consists of two laboratory visits which span a 15-day period. To complete the entire research study, you must complete both visits. During Visit 1 and Visit 2, you will be asked to come to the SIA-NUS Digital Aviation Corporate Laboratory (National University of Singapore, Innovation 4.0, 3 Research Link, Singapore 117602). The cabin simulator is acoustically shielded to minimize auditory disturbances from other parts of the building and is designed to mimic the business class environment inside an aircraft, including business class seats, overhead bins, and functional lavatories. The cabin simulator can accommodate up to 8 research participants at one time. Environmental parameters in the cabin (e.g., oxygen, humidity, temperature, sound, vibration, light) can be adjusted to reflect the conditions experienced by passengers at a common cruising altitude. You might not have internet access in the cabin, and you cannot leave the cabin simulator unless you wish to end the study.

During each study visit, you will be assigned a seat. After being oriented to the cabin simulator, you are expected to remain in your seat except for short breaks to stretch or use the bathroom. Sensors such as pressure mats, angle sensors, wireless textiles and eye trackers may be placed in and around the seats to measure movement, pressure, posture, and sleep behaviour throughout the simulated flight. Video and/or audio recordings will be used to perform kinematic analyses (e.g., body movements & posture) related to your activities, sleep, and comfort. While you are in the cabin simulator, you may be monitored on a closed-circuit television to make sure you are safe. There are no cameras in the bathroom. The cabin simulator will contain a communication device (intercom or call lights) so that you can communicate with staff members in the control room. Research staff will be on-site for the entire study and they will interact with you frequently to carry out research procedures. Therefore, you will not have much privacy during most of the study.

What happens before the study visit?
1. No drugs or medications: If you need medications for your health, then you should not participate in this study. You should contact the study Principal Investigator or members of the research team if you have any questions about what substances or drugs are allowed.

2. Sleep-wake monitoring: During the week before each study visit, you will be required to keep a regular sleep-wake schedule with 7 to 9 hours of time in bed for sleep each night, with a bedtime no later than 2:00 AM, and a wake-time no later than 9:00 AM. You will be asked to keep track of the times you go to sleep and wake up in a daily online diary and via Telegram messages. You will not be allowed to take any naps during these two weeks, except during the laboratory visits. You will also be asked to wear an actigraphy watch to measure your sleep-wake pattern. The actigraphy watch is worn like an ordinary wrist-watch. It has a motion sensor and light sensor. You should wear the actigraphy watch at all times from the time you collect it until the end of the study. You should wear the watch while you are awake and while you are sleeping. You should remove the watch only during activities that might result in damage to the watch (contact sports, swimming, diving). You will be asked to sign an agreement indicating that you will return the actigraphy watch to us at the end of the study. Even if you decide to withdraw from the study, you are expected to return the actigraphy watch.

3. One night of short sleep: The night before each study visit, you will be required to restrict your sleep to 5 hours, with a bedtime of 01:30 AM and a wake-time of 06:30 AM. You are expected to arrive at our laboratory by 08:30 AM for your simulated flight.

What happens during the study visit?
Experimental conditions: During each visit, you will undergo a simulated business class flight lasting several hours. You will arrive in the morning (about 08:30 AM) to board the flight and remain in the laboratory until the early evening (about 07:00 PM). You will be given lunch and beverages with access to snacks. You may not be allowed to bring your own food/drinks. Please inform us of any allergies so that we can provide appropriate meals, beverages and snacks accordingly. You will be given a 1 to 2 hour nap opportunity in the mid-afternoon during each visit. Some aspects of the cabin environment may be different between the 2 study visits (e.g., temperature, lighting, services and amenities).

Sleep/wake recordings: We will record the following signals when you awake and during the scheduled nap:
• Your brain wave signals (electroencephalogram, EEG)
• Your eye movement signals (electrooculogram, EOG)
• Your muscle activity signals (electromyogram, EMG)
• Your heart beat activity (electrocardiogram, ECG)

We will place small electrodes on the skin of your scalp, face, chin and chest. A special glue and tape will hold the electrodes in place. When it is time for the electrodes to be removed, the glue is removed with water.

Vital signs: During each study visit, we will take your vital signs including your temperature, heart rate, respiratory rate, and blood pressure at least once.

Event marking: You may have a clicker for you to register the timepoints where you may feel any changes to your comfort level in the seat.

Computer tests: You will be required to carry out computer tests that measure different types of performance and feelings. The tests will be given several times during the simulated flight. You may be given short breaks between tests. Each group of tests will last 2 to 15 minutes. Examples of tests that you may take include:
1) The psychomotor vigilance test, which is a simple reaction time test used to assess visual attention;
2) The digit symbol substitution task, in which you are shown a symbol and you are asked to find its match among a panel of symbols;
3) The Karolinska sleepiness scale, in which you are asked to rate your sleepiness on a 9-point scale;
4) The Samn-Perelli Fatigue scale, in which you are asked to rate your degree of fatigue on a 7-point scale;
5) Mood scales, in which you are asked to rate how you are feeling on a line labelled with opposite word pairs (e.g., happy-sad, alert-sleepy; energized-fatigued);
6) Positive and Negative Affect Scales (PANAS), in which you are asked to rate your mood based on 20 positive and negative adjectives (e.g. excited, nervous) on a 5-point scale;

Questionnaires: You will be asked to complete questionnaires & surveys about your sleep and comfort. Examples of these include: 1) Pre-flight questionnaire, to assess your travel profile and usual sleep habits prior to the laboratory visit 2) In-flight questionnaire, to assess discomfort at various anatomical points of the body. This will be assessed periodically during the study, ranging from every 10 minutes during some parts of the study to hourly during other parts. 3) Post-flight questionnaire, to evaluate factors that affected sleep and comfort, and to collect feedback from you.

Do I get reimbursed?
You will receive $200 (cash or voucher equivalent) for completing all study visits as follows:
First study visit: $80
Second study visit: $120

The reimbursement takes into account the time that you spend wearing the actigraphy watch, filling out the sleep/wake diaries. You do not get paid for the screening questionnaires that you already completed. Therefore, if you complete the entire research study you will be reimbursed $200 after the end of the final study visit (in one lump sum). If you decide to withdraw before the last visit, you will be reimbursed pro-rata based on the parts you have completed.

Questions: Please contact us at siacorplab-wp4@nus.edu.sg

To indicate your interest, please drop us an email.

Ongoing Studies

[CLOSED] Developing Evidence-Based Interventions to Improve Sleep Quality and Passenger Comfort in Aviation