Sleep and Circadian Treatments for Shift Workers

There are three components to this study: a Field Trial, a Shift Worker Survey, and Focus Groups. The Investigators will study the effectiveness, feasibility, and acceptability of an 8-h sleep intervention in older night workers in an operational environment. The overall goal of the Field Trial is to minimize sleep deficiency and negative outcomes resulting from that, including sleepiness and performance impairments during night shift work. The Shift Worker Survey is designed to understand some of the demographic and operational factors that enable or inhibit the ability of individual shift workers to adopt this intervention. The Focus Groups are designed to glean in-depth information from older shift workers who indicate that they are unable or unwilling to adopt an 8-h sleep timing intervention. Understanding these factors will assist in refining and targeting the intervention to those individuals who will be most likely to benefit from the intervention sleep timing strategy.

The overall goal of the Field Trial is to minimize sleep deficiency and negative outcomes resulting from that, including sleepiness and performance impairments during night shift work. The experimental protocol is divided into two blocks, the Baseline block and the Intervention block, where participants will work at least 3 night shifts in a row within each block. For at least one week prior to the baseline block participants will work their usual shift schedule (i.e., no vacation/scheduled days off). The investigators will recruit up to 200 health care workers in order to have up to 75 health care workers complete the entire Field Trial. Potential participants will be employed older health care workers who work a minimum number of 8-h night shifts per month and who are in the greater Boston area. The Shift Worker Survey is designed to understand some of the demographic and operational factors that enable or inhibit the ability of individual shift workers to adopt the sleep intervention that will be tested in the Field Trial. The investigators will use a web-based survey consisting of ~70 questions developed and administered using REDCap. The complete questionnaire will take approximately 20-30 minutes to complete. The study will enroll up to 1,000 employed individuals (20 or more hours per week) whose work includes overnight shifts, with a minimum criterion of at least 4 night shifts a month. Health Care Workers who complete the Shift Worker Survey will be given the option to complete an additional Health Care Worker's Questionnaire at the end of the basic Shift Worker Survey. Those whose responses meet inclusion/exclusion criteria for the Field Trial will be informed at the end of the Shift Worker Survey that they may be eligible for the Field Trial. The goal of the Focus Groups is to gain information on the feasibility and acceptability of the fixed 8-h sleep schedule from the participants' perspective. Investigators will seek to learn more information about the current sleep strategies they use on a regular basis, and both the facilitating and challenging aspects of the fixed-sleep countermeasure (e.g., individual, intrapersonal and organizational barriers to implementation of fixed 8-h sleep, recommended modifications to the fixed 8-h sleep schedule that would make it more user-friendly while maintaining scientific validity). Each of the focus groups will consist of 4-6 individuals to stimulate discussion without leaving participants out, and will last 60-90 minutes. The investigators aim to enroll up to 60 individuals in Focus Groups. In addition to the health care workers who took part in the Field Trial, the investigators will invite night shift workers who complete the Shift Worker Survey but indicate their inability to comply with a fixed 8-h sleep schedule to attend a Focus Group discussion.

During the intervention block of the Field Trial, at the end of the first night shift, the participant will be told about their randomization group. In the control group (Group A), participants will not be given any instructions about the timing or duration of their sleep, but will be instructed to follow their usual night shift sleep routine.

In the 8-h afternoon-evening sleep intervention group (Group B), participants will be instructed to go to bed between 13:00 and 14:00 (depending on their individual commute time) and to remain in bed attempting to sleep for 8 hours (until 21:00-22:00) before the next two night shifts.

In the 8-h free sleep group (Group C), participants will be instructed to remain in bed for 8 continuous hours before the next two night shifts, but will not be given any instruction regarding which 8 hours they should sleep.

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.

Subjective Sleep quality (refreshment) averaged for intervention nights 2 and 3 will be compared between groups.(

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 KSS score taken at the end of the final night shift (night shift 3) during the intervention block will be compared between groups.

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 will use the number of lapses of attention (RT > 500msec) as our outcome.

PVT mean lapses of attention measured at the end of the final night shift (night shift 3) during the intervention block will be compared between groups.

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 to the indicated point will be measured in mm and reported as subjective energeticness.

Subjective Energy measurements taken at the end of the final night shift (night shift 3) in the intervention block will be compared between groups.

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 to the indicated point will be measured in mm and reported as Subjective Stress.

Subjective Stress via VAS measurements taken at the end of the final night shift (night shift 3) in the intervention block will be compared between groups.

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 to the indicated point will be measured in mm and reported as Subjective Calmness.

Subjective Calmness via VAS measurements taken at the end of the final night shift (night shift 3) in the intervention block will be compared between groups.

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 to the indicated point will be measured in mm and reported as Subjective Health.

Subjective Health via VAS measurements taken at the end of the final night shift (night shift 3) in the intervention block will be compared between groups.

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.

Subjective Alertness via VAS measurements taken at the end of the final night shift (night shift 3) in the intervention block will be compared between groups.

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.

OFER15 scores from the end of the third night shift in the Intervention block will be compared between groups.

The investigators will collect subjective measures of daily stress using a validated questionnaire, the Daily Stress Inventory (DSI), a 58-item self-report measure that allows a person to indicate events that they have experienced in the past 24 hours. After indicating which events occurred, individuals rate the stressfulness of those events on a Likert scale ranging from 1 (occurred but was not stressful) to 7 (caused me to panic).

Subjective stress will be assessed immediately after the third night shift in the Intervention block and will be compared between groups.

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).

WHOQOL-Bref will be taken immediately after the third night shift in the Intervention block and will be compared between groups.

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.

Salivary Cortisol will be assessed immediately after the third night shift in the Intervention block and levels will be compared between groups.

Field Trial - Inclusion Criteria: Age 50-65 years Health care workers who work a minimum of 4 night shifts (8-4) per month Must live in the greater Boston area Must report an ability to work three successive 8-h night shifts during two weeks Must report an ability to spend 8 consecutive hours in bed attempting to sleep prior to the final two successive night shifts in the second study week Must have a typical commute time between home and place of work of less than one hour Exclusion Criteria: Non-optional activities that would interfere with the participant's ability to remain in bed attempting to sleep if randomized to an 8-h sleep group Prescription or over-the-counter medication(s) known to affect sleep [e.g., hypnotics] or alertness [e.g., antihistamines]