Simulated Night Shift for Circadian Rhythm Disorder
(SPOTLIGHT Trial)
Recruiting in Palo Alto (17 mi)
Age: 18 - 65
Sex: Any
Travel: May Be Covered
Time Reimbursement: Varies
Trial Phase: Academic
Recruiting
Sponsor: University of Colorado, Denver
Must be taking: Oral contraceptives
Must not be taking: Antidepressants, Neuroleptics, Tranquilizers, others
Disqualifiers: Obesity, Smoking, Psychiatric disorders, others
No Placebo Group
Trial Summary
What is the purpose of this trial?This trial will test if working night shifts affects bone health by increasing stress levels. It will also check if returning to a normal sleep schedule can reverse any negative effects.
Will I have to stop taking my current medications?
The trial requires participants to stop using medications that affect bone turnover or sleep, such as glucocorticoids, osteoporosis medications, and sleep medications, at least one month before the study. If you are on these medications, you may need to stop taking them to participate.
What data supports the effectiveness of the treatment Simulated Night Shift Work for Circadian Rhythm Disorder?
Research suggests that adjusting light exposure and sleep schedules can help align the body's internal clock with night shift work, improving sleep quality and reducing fatigue. This approach, known as circadian adaptation, has been shown to help night shift workers better adjust to their schedules, potentially improving their overall health and safety.
12345Is simulated night shift work generally safe for humans?
Simulated night shift work can lead to increased crash risk during morning commutes, disturbed sleep, and health issues like cardiovascular risk and sleep disorders. These effects are due to the disruption of the body's natural sleep-wake cycle, which can cause excessive sleepiness and reduced alertness.
678910How does the Simulated Night Shift treatment differ from other treatments for circadian rhythm disorder?
The Simulated Night Shift treatment is unique because it uses controlled light and dark cycles to help adjust the body's internal clock to align with night work and day sleep schedules, unlike other treatments that might focus on medication or lifestyle changes.
15111213Eligibility Criteria
Healthy adults aged 20-40, who sleep 7-9 hours at night and are fully vaccinated against COVID-19. Women must be premenopausal, on oral contraception, not breastfeeding. Participants should commit to a study including inpatient stays and wear a wrist monitor for activity tracking.Inclusion Criteria
I am a premenopausal woman not breastfeeding and on birth control pills.
Willing and able to complete a sleep diary, wear a wrist actigraphy monitor and complete a 3-6 week research study including two 4-night inpatient stays.
Willing and able to complete a sleep diary, wear a wrist actigraphy monitor and complete a 3-6 week research study including two 4-night inpatient stays
+4 more
Exclusion Criteria
You have smoked within the past year.
Your bone density is very low compared to the average for your age and gender.
Your vitamin D level is less than 20 ng/mL.
+23 more
Trial Timeline
Screening
Participants are screened for eligibility to participate in the trial
2-4 weeks
Baseline
Participants undergo baseline measurements and sleep under normal conditions
1 night
Inpatient stay
Simulated Night Shift Work
Participants experience simulated night shift work with 3-hour afternoon naps and 12-hour night shifts
3 nights
Inpatient stay
Follow-up
Participants are monitored for changes in bone turnover markers after resuming normal sleep patterns
4 weeks
Participant Groups
The trial is testing how simulated night shift work affects bone metabolism by measuring bone turnover markers and sympathetic nervous system tone. It involves two sets of four-night inpatient stays with follow-up to see if normal patterns reverse any changes.
2Treatment groups
Experimental Treatment
Active Control
Group I: Simulated Night Shift WorkExperimental Treatment1 Intervention
Two inpatient stays, each involving a baseline night, followed by a 3-hour afternoon nap opportunity, and then three 12-hour night shifts, with 8-hour daytime sleep opportunity in between.
Group II: Control (8 hours nocturnal sleep)Active Control1 Intervention
Inpatient protocol involves 8-hour sleep opportunity during the biological night throughout.
Find a Clinic Near You
Research Locations NearbySelect from list below to view details:
CU AnschutzAurora, CO
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Who Is Running the Clinical Trial?
University of Colorado, DenverLead Sponsor
National Heart, Lung, and Blood Institute (NHLBI)Collaborator
References
How the circadian rhythm affects sleep, wakefulness, and overall health: background for understanding shift work disorder. [2012]It is estimated that 15 to 25% of the U.S. labor force works night, evening, or rotating shifts. These non-traditional schedules can affect the circadian rhythm, a self-sustained rhythm of biological processes that plays an important role in modulating sleep/wake function, resulting in circadian rhythm sleep disorder, shift work type, usually referred to as shift work disorder. The disorder consists of a constant or recurrent pattern of sleep interruption that results in insomnia when sleep is needed and excessive sleepiness during waking hours. Clinicians need more information about the role of the circadian rhythm in human functioning as well as the pathophysiology, prevalence, and consequences of shift work disorder, so that they can recognize and diagnose this problem in clinical practice.
Scheduling of sleep/darkness affects the circadian phase of night shift workers. [2013]Shift work results in a misalignment between circadian timing and the sleep/wake schedule, leading to irregular and poor quality sleep. Inconsistent input from the daily light cycle further interferes with circadian entrainment. It has been hypothesized that scheduling the sleep/dark cycle on the night shift could aid in promoting adaptation to night shift work by facilitating appropriate phase shifts. In a simulated shift-work study, we compared the ability of two sleep/dark schedules to shift circadian phase. Our results indicate that scheduled sleep/darkness can aid in adaptation to night shift work by inducing both advance and delay phase shifts, depending on the timing of the sleep schedule, although the size of the phase shifts are not sufficient to produce complete adaptation to the night shift. These results have applications to night shift workers, particularly in occupations in which alterations in the timing of light exposure cannot be achieved during working hours.
Implementation of interventions designed to promote healthy sleep and circadian rhythms in shiftworkers. [2021]Shiftwork is a significant risk factor for a host of negative health and safety outcomes, which have been at least partly attributed to disturbances of the circadian timing system. As a result, an entire sub-field of chronobiology has been devoted to developing and evaluating countermeasures for circadian misalignment, sleep disruption, fatigue, and other issues associated with shiftwork. Much of this research takes place under highly controlled laboratory conditions due to the necessity of accurately characterizing individual rhythms, both for intervention design and assessment of efficacy. Applied studies of interventions for shiftworkers are, by their nature, more complicated, often demonstrating less consistent findings. While this, in part, reflects execution under less rigorously controlled conditions, it may also stem from variability in implementation approaches. A systematic review of published studies (through May 2017) of interventions designed to enhance circadian health in shiftworkers was conducted to determine the frequency and quality of the assessment of implementation as well as barriers and enablers to implementation. A search of PubMed, PsychINFO, Web of Science, and CINAHL databases yielded a total of 5368 unique references. After a title and abstract screen, 323 proceeded to full-text review; 68 of those met final criteria for data extraction. Implementation was assessed to some degree in 60.3% of those 68 articles. Where it was assessed, the mean quality score on a scale from 1 to 5 (1 = very little, 3 = moderate, 5 = very in-depth) was 2.56. One or more enablers were identified in just 17 of the 68 studies (25.0%), and barriers in just 18 (26.5%). Implementation of these interventions is a critical but seldom-acknowledged component of their uptake and effectiveness, and we highly recommend that future shiftworker intervention research make an effort to incorporate formalized assessments of implementation and/or hybrid effectiveness-implementation approaches.
Sleep and circadian misalignment for the hospitalist: a review. [2015]Shift work is necessary for hospitalists to provide on-site 24-hour patient care. Like all shift workers, hospitalists working beyond daylight hours are subject to a misalignment between work obligations and the endogenous circadian system, which regulates sleep and alertness patterns. With chronic misalignment, sleep loss accumulates and can lead to shift work disorder or other chronic medical conditions. Hospitalists suffering from sleep deprivation also risk increased rates of medical errors. By realigning work and circadian schedules, a process called circadian adaptation, hospitalists can limit fatigue and potentially improve safety. Adaptation strategies include improving sleep hygiene before work, caffeine use at the start of the night shift, bright light exposure and planned naps during the shift, and short-term use of a mild hypnotic after night work. If these attempts fail and chronic fatigue persists, then a diagnosis of shift work disorder should be considered, which can be treated with stronger pharmacotherapy. Night float scheduling strategies may also help to limit chronic sleep loss. More research is urgently needed regarding the sleep patterns and job performance of hospitalists working at night to improve scheduling decisions and patient safety.
How to use light and dark to produce circadian adaptation to night shift work. [2019]The circadian rhythms of night shift workers do not usually adjust to their unusual work and sleep schedules, reducing their quality of life and producing potentially dangerous health and safety problems. This paper reviews field studies of simulated night work in which shifted light-dark cycles were constructed with artificial bright or medium-intensity light to produce circadian adaptation, ie the shifting of circadian rhythms to align with night work and day sleep schedules. By using these studies we describe fundamental principles of human circadian rhythms relevant to producing circadian adaptation to night shift work at a level designed for the reader with only a basic knowledge of circadian rhythms. These principles should enable the reader to start designing work/sleep-light/dark schedules for producing circadian adaptation in night shift workers. One specific schedule is presented as an example. Finally, we discuss phase-response curves to light and clarify common misconceptions about the production of circadian rhythm phase shifts.
The likelihood of crashing during a simulated post-work commute decreases across a week of consecutive night shifts. [2021]The aim of this study was to assess the effect of working multiple, consecutive night shifts on crash risk during the morning commute. Participants (36 F, 36 M, aged 23.1 ± 3.6 y) completed a laboratory-based shiftwork protocol with seven consecutive night shifts (23:00-07:00 h) that each started and ended with a 20 min simulated commute. Compared to the corresponding pre-work commutes, the likelihood of crashing during the post-work commutes was 11.0-, 8.5-, and 5.6-fold higher at the start, middle, and end of the week, respectively. The results of this simulation study indicate that crash risk is relatively high during the morning commute but declines throughout a week of night work.
Understanding circadian rhythms: a holistic approach to nurses and shift work. [2018]When night shift nurses drive home at 7:30 a.m., the daylight resets their circadian pacemakers in the retina. This daylight exposure amplifies desynchronization of the circadian rhythm. It was found that 3:00 a.m. to 3:00 p.m. and 3:00 p.m. to 3:00 a.m. shifts produced less physiological and emotional stresses. Increased awareness of circadian rhythms may help to reduce the multiple risks to nurses' health and enhance quality of life. This article presents the scientific principles of circadian rhythms and their effects on shift workers' health and illnesses. There is a significant decrease in job performance and in satisfaction and quality of patient care. Statistics indicate that errors, injuries, sick days, and accidents are higher for nurses' working rotating shifts. Eleven recommendations provide ideas to support nurses holistically.
Shift work and the assessment and management of shift work disorder (SWD). [2022]Nearly 20% of the labor force worldwide, work shifts that include work hours outside 07:00 h to 18:00 h. Shift work is common in many occupations that directly affect the health and safety of others (e.g., protective services, transportation, healthcare), whereas quality of life, health, and safety during shift work and the commute home can affect workers in any field. Increasing evidence indicates that shift-work schedules negatively influence worker physiology, health, and safety. Shift work disrupts circadian sleep and alerting cycles, resulting in disturbed daytime sleep and excessive sleepiness during the work shift. Moreover, shift workers are at risk for shift work disorder (SWD). This review focuses on shift work and the assessment and management of sleepiness and sleep disruption associated with shift work schedules and SWD. Management strategies include approaches to promote sleep, wakefulness, and adaptation of the circadian clock to the imposed work schedule. Additional studies are needed to further our understanding of the mechanisms underlying the health risks of shift work, understanding which shift workers are at most risk of SWD, to investigate treatment options that address the health and safety burdens associated with shift work and SWD, and to further develop and assess the comparative effectiveness of countermeasures and treatment options.
Effects of Shift Work in a Sample of Italian Nurses: Analysis of Rest-Activity Circadian Rhythm. [2021]Shift work can lead to circadian desynchronization due to temporary misalignment between working hours and physiological and behavioral functioning, resulting in compromised health, insomnia, worsening of sleep quality, reduced ability to work during waking hours, and increased cardiovascular risk. We evaluated the effects of shift work on the rest-activity circadian rhythm (RAR) and health status of Italian orthopaedic nurses. The study population was 59 nurses: 44 worked the night shift and 15 worked the day shift. All carried out continuous 5-day actigraphic monitoring to assess RAR, including both the working and the rest period. The rhythmometric analysis showed that, during the working period, the night shift nurses had a significantly lower amplitude than the day shift nurses (p < 0.001), and the acrophase was significantly different between the two groups (p < 0.01). When we stratified the two groups by median body mass index (<25 kg/m2 normal weight and ≥25 kg/m2 overweight), during the working period, we noted a significantly lower amplitude for both the normal weight and the overweight nurses who worked the night shift (p < 0.01 and p < 0.001, normal weight and overweight respectively). The current findings suggest the need for further study of the relationship between activity levels and shift work.
Impacts of shift work on sleep and circadian rhythms. [2022]Shift work comprises work schedules that extend beyond the typical "nine-to-five" workday, wherein schedules often comprise early work start, compressed work weeks with 12-hour shifts, and night work. According to recent American and European surveys, between 15 and 30% of adult workers are engaged in some type of shift work, with 19% of the European population reportedly working at least 2 hours between 22:00 and 05:00. The 2005 International Classification of Sleep Disorders estimates that a shift work sleep disorder can be found in 2-5% of workers. This disorder is characterized by excessive sleepiness and/or sleep disruption for at least one month in relation with the atypical work schedule. Individual tolerance to shift work remains a complex problem that is affected by the number of consecutive work hours and shifts, the rest periods, and the predictability of work schedules. Sleepiness usually occurs during night shifts and is maximal at the end of the night. Impaired vigilance and performance occur around times of increased sleepiness and can seriously compromise workers' health and safety. Indeed, workers suffering from a shift work sleep-wake disorder can fall asleep involuntarily at work or while driving back home after a night shift. Working on atypical shifts has important socioeconomic impacts as it leads to an increased risk of accidents, workers' impairment and danger to public safety, especially at night. The aim of the present review is to review the circadian and sleep-wake disturbances associated with shift work as well as their medical impacts.
Circadian rhythm disturbances and sleep disorders in shift workers. [2015]Employment which requires frequent shift rotation may lead to the development of specific sleep disorders. Delayed sleep phase (DSP) insomnia, a syndrome identified recently, can greatly impair an individual's circadian rhythm-dependent functions; it can occur when shift work disrupts normal sleep-waking schedules. Disorders of excessive daytime sleepiness, such as narcolepsy, occur in some subjects after they have been subjected to frequently rotating shifts. Understanding the problems associated with circadian rhythm disturbances and their interaction with sleep disorders is particularly important in industrial medicine; any clinician whose patients are subjected to frequent shift rotations should consider the effects of disrupted sleep-waking schedules.
Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial. [2020]Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment.
Identifying shift worker chronotype: implications for health. [2019]Shift workers are at risk for developing serious health issues due to short sleep. One cause of short sleep is circadian misalignment: sleep time is not synchronized with the body's natural circadian rhythms. Although circadian rhythms are strongly driven by the light/dark cycle, humans have individualized sleep time preferences (chronotypes) based on genetics, development, and external influences. Evening chronotype individuals fall asleep later than average and have a higher risk for developing various noncommunicable diseases. What is unclear is the association between chronotype, shift work, and risks for acquiring chronic conditions. This review is focused on shift worker chronotype and associations with obesity. Because of the paucity of research, other health issues connected with circadian misalignment were included, allowing for a total of 21 research studies. Evidence from this review supports chronotype and certain health issues are associated with shift work, even after adjusting for short sleep duration. In addition, there is evidence to support future research on how shift worker chronotype matched with shift timing impacts worker health. Through better understanding of this interface, occupational health providers can provide more comprehensive worker education on the risks associated with shift work and sleep disturbances.