Trial Outcomes & Findings for Sleep and Circadian Treatments for Shift Workers (NCT NCT03813654)

Recruitment took place between September 2019 and November 2022. All recruitment was via advertisements placed online, in newsletters, and through email lists.

Enrollment was assigned upon start of the Baseline period, but participants were not informed of their randomization until after the first night shift of the Intervention period.

Sleep and Circadian Treatments for Shift Workers

TST is calculated as minutes of sleep in the main sleep episode between shifts, derived from actigraphy data collected in 60 s epochs. The investigators will use a commercial software package to score the sleep. For control group participants who will sleep ad-lib, TST will be calculated for the major sleep episode but also will be summed across sleep episodes if they sleep in more than one bout.

FI will be calculated as the number of times that sleep was terminated after 1 minute, expressed as a percentage of total estimated sleep time, using actigraphy data and commercial software to calculate it.

WASO is an objective sleep quality measure and will be calculated as the duration (in minutes) of all awakenings during the main sleep episode measured with actigraphy, and calculated using commercial software.

Participants will report their subjective sleep quality daily upon awakening from the main sleep episode. Multiple measures of subjective sleep quality will be assessed, but the investigators will report how refreshed the participant feels after awakening as the outcome. This is rated on a 7-point scale, where 7 is the best and 1 is the worst.

Participants will complete the Karolinska Sleepiness Scale (KSS) as a measure of subjective alertness immediately following each night shift. The KSS is a Likert scale ranging from 1, extremely alert, to 9, extremely sleepy.

The psychomotor vigilance task (PVT) is a test of visual reaction time (RT) in which the participant is asked to maintain the fastest possible RTs to a simple visual stimulus for several minutes. The inter-stimulus interval varies randomly between 2-10 seconds. While there are a number of standard performance metrics that can be obtained from each PVT, we have looked at the slowest 10% of responses.

A Visual Analogue Scale (VAS) will be used to assess subjective energy level. The VAS consists of a 100mm horizontal line with each end of the line labeled with the extremes of a subjective continuum, e.g. energetic-sluggish. The Participant indicates a position on the line that best describes how they feel at that moment. Distance from the left end of the scale (0) to the indicated point will be measured in mm and reported as subjective energeticness. Thus, scores on the scale range from 0 to 100 with lower scores indicating greater subjective energy.

A Visual Analogue Scale (VAS) will be used to assess subjective stress.The VAS consists of a 100mm horizontal line with each end of the line labeled with the extremes of a subjective continuum, e.g. relaxed-stressed. The Participant indicates a position on the line that best describes how they feel at that moment. Distance from the left end of the scale (0) to the indicated point will be measured in mm and reported as Subjective Stress. Thus, scores on the scale range from 0 to 100 with higher scores indicating greater subjective stress.

A Visual Analogue Scale (VAS) will be used to assess subjective Calmness. The VAS consists of a 100mm horizontal line with each end of the line labeled with the extremes of a subjective continuum, e.g. calm-excited. The Participant indicates a position on the line that best describes how they feel at that moment. Distance from the left end of the scale (0) to the indicated point will be measured in mm and reported as Subjective Calmness. Thus, scores on the scale range from 0 to 100 with lower scores indicating greater subjective calmness.

Visual Analogue Scales (VAS) will be used to assess subjective health. VAS consist of a 100mm horizontal line with each end of the line labeled with the extremes of a subjective continuum, e.g. healthy-sick. The Participant indicates a position on the line that best describes how they feel at that moment. Distance from the left end of the scale (0) to the indicated point will be measured in mm and reported as Subjective Health. Thus, scores on the scale range from 0 to 100 with lower scores indicating greater subjective health.

Participants will complete the Visual Analog Scale (VAS) as a measure of subjective alertness three times per night shift: Once just before the night shift, once during their shift break, and once immediately following the night shift. The VAS consists of a 100mm horizontal line with each end of the line labeled with the extremes of a subjective continuum, e.g. sleepy-alert. Participants will indicate a position on the line that best describes how they feel at that moment. Distance from the left end of the scale to the indicated point will be measured in mm and reported as Subjective Alertness with higher scores indicating greater subjective alertness.

The Occupational Fatigue Exhaustion Recovery Scale (OFER 15), which consists of 15 questions about acute fatigue and recovery between shifts, will be used. Each of the 15 questions is answered on a Likert scale which ranges from 0 (Strongly Disagree) to 6 (Strongly Agree). The OFER15 will be completed immediately after the third night shift in the Baseline block and at the end of the third night shift in the Intervention block.

The investigators will collect subjective measures of daily stress using a validated questionnaire, the Perceived Stress Scale (PSS), a 10-item self-report measure that allows a person to indicate stressful events that they have experienced in the past week. Each question is answered on a 5-item scale indicating the frequency, from 1 (never) to 5 (very often).

The investigators will use a validated questionnaire, the WHOQOLBref, a 26 item questionnaire suitable for field studies, which asks a series of questions about life, health, energy, and personal satisfaction, to assess Quality of Life. The questionnaire contains 4 separately scored domains: Physical Health, Psychological, Social Relationships, and Environment. Each domain contains several questions and ask participants to provide a response on a Likert Scale ranging from 1 to 5, with higher numbers indicating a higher quality of life (aside from 3 negatively phrased items).

The investigators will collect a single saliva sample at the end of the final night shift in the Baseline block and the Intervention block. The sample will be frozen and later assayed to assess cortisol level (in micrograms per deciliter, μg/dL). Higher cortisol levels will be indicative of greater stress.