0006 The Role of Stress in Sleep in Night Shift Workers: Going Beyond Circadian Misalignment

Abstract Introduction Despite a growing need for nighttime work, few studies have characterized the causes of sleep disturbance in night shift workers beyond circadian misalignment. Recent research suggest that high sleep reactivity to stress (a predisposition for sleep disturbance due to stress) may also lead to sleep difficulties in shift workers. This study investigated if sleep reactivity is an independent predictor of daytime sleep disturbances after controlling for circadian phase. Methods Night shift workers (N= 48) completed an 8 hour polysomnography (PSG) during the daytime following a night shift (9am - 4pm). Circadian phase was measured using melatonin assays of saliva samples collected over 24 hours under dim light (<10 lux; Dim Light Melatonin Onset [DLMO]). Sleep reactivity was measured using the Ford Insomnia Response to Stress Test (FIRST). Linear regressions were conducted with PSG sleep parameters as outcome variables: difficulty falling asleep (Sleep Onset Latency [SOL] and Latency to Persistent Sleep [LPS]), difficulty staying asleep (Wake After Sleep Onset [WASO]), and sleep duration (Total Sleep Time [TST]). FIRST was tested as a predictor controlling for DLMO. Results After controlling for circadian phase, higher FIRST scores was associated with more difficulty staying asleep (WASO: t[45]=4.059, p<0.001) and shorter sleep duration (TST: t[45] = -4.403, p<0.0001), but not predictive of difficulty falling asleep (SOL: p>0.05). However, higher FIRST scores did predict a longer latency to persistent sleep (LPS: t[45]=2.272, p<0.05). Conclusion These results suggest that sleep reactivity to stress and circadian misalignment are independent processes that are both associated with disrupted daytime sleep in night shift workers. Given that night shift work can also cause psychosocial stress, treatments focused on circadian misalignment alone may not be sufficient. Our study highlights the need to consider sleep reactivity in the clinical management of shift work disorder. Support Support for this study was provided to PC by NHLBI (K23HL138166).

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0007 Daytime Sleep in Night Shift Workers: Quantifying the Role of Circadian Misalignment

SLEEP ◽

10.1093/sleep/zsaa056.006 ◽

2020 ◽

Vol 43 (Supplement_1) ◽

pp. A3-A3

Author(s):

E Mann ◽

C Sagong ◽

A Cuamatzi Castelan ◽

M Singh ◽

T Roth ◽

...

Keyword(s):

Sleep Duration ◽

Sleep Disturbances ◽

Night Shift ◽

Sleep Onset ◽

Sleep Onset Latency ◽

Shift Workers ◽

Circadian Misalignment ◽

Daytime Sleep ◽

Falling Asleep ◽

Dim Light

Abstract Introduction Circadian misalignment is commonly cited as a culprit of daytime sleep disturbances in night shift workers; however, the specific impact and magnitude that circadian misalignment has on daytime sleep has not been well-characterized in larger samples of night shift workers. Methods Participants included fixed-night shift workers (n=52, ages 18–50) who completed an 8-hour daytime polysomnography (PSG) in the lab following a night shift. Measures of sleep disturbances included: difficulty falling asleep (sleep onset latency [SOL], latency to persistent sleep [LPS]), difficulty staying asleep (sleep efficiency [SE], wake after sleep onset [WASO]), and sleep duration (total sleep time [TST]). Melatonin samples were collected hourly for 24 hours under dim light (<10 lux) and used to determine dim light melatonin offset (DLMOff). Circadian misalignment (CM) was calculated as the time difference between bedtime and DLMOff (higher values represented sleeping after DLMOff), and correlated with PSG sleep variables. Results CM was significantly associated with difficulty staying asleep (WASO: r=0.48, p<0.001; SE: r=-0.45, p<0.001), and sleep duration (TST: r=-0.38, p<0.01). Specifically, every 3 hours of CM on average added 19.2 minutes of WASO and reduced TST by 15 minutes. In contrast, CM was not significantly correlated with sleep onset difficulties (SOL: r=-0.27; LPS: r=-0.02). Conclusion These data suggest that circadian misalignment in shift workers may be a better predictor of difficulties staying asleep and sleep duration during the day relative to difficulties falling asleep. Because longer work hours (10–12 hours) are common in night shift worker, it may be that sleep initiation difficulties associated with circadian misalignment is masked by elevated fatigue or an increased homeostatic drive from prolonged wakefulness. These results may help guide decisions about the magnitude of phase shifts required (e.g., with light therapy) for the desired improvement in daytime sleep. Support Support for this study was provided to PC by the NHLBI (K23HL138166)

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Predicting circadian misalignment with wearable technology: validation of wrist-worn actigraphy and photometry in night shift workers

SLEEP ◽

10.1093/sleep/zsaa180 ◽

2020 ◽

Author(s):

Philip Cheng ◽

Olivia Walch ◽

Yitong Huang ◽

Caleb Mayer ◽

Chaewon Sagong ◽

...

Keyword(s):

Assessment Tool ◽

Night Shift ◽

Future Research ◽

Shift Workers ◽

Circadian Misalignment ◽

Circadian Phase ◽

Model Code ◽

Sleep Timing ◽

Wrist Actigraphy ◽

Dim Light

Abstract Study Objectives A critical barrier to successful treatment of circadian misalignment in shift workers is determining circadian phase in a clinical or field setting. Light and movement data collected passively from wrist actigraphy can generate predictions of circadian phase via mathematical models; however, these models have largely been tested in non-shift working adults. This study tested the feasibility and accuracy of actigraphy in predicting dim light melatonin onset (DLMO) in fixed night shift workers. Methods A sample of 45 night shift workers wore wrist actigraphs before completing DLMO in the laboratory (17.0 days ± 10.3 SD). DLMO was assessed via 24 hourly saliva samples in dim light (<10 lux). Data from actigraphy were provided as input to a mathematical model to generate predictions of circadian phase. Agreement was assessed and compared to average sleep timing on non-workdays as a proxy of DLMO. Model code and an open-source prototype assessment tool are available (www.predictDLMO.com). Results Model predictions of DLMO showed good concordance with in-lab DLMO, with Lin’s concordance coefficient of 0.70, which was twice as high as agreement using average sleep timing as a proxy of DLMO. The absolute mean error of the predictions was 2.88 h, with 76% and 91% of the predictions falling with 2 and 4 h, respectively. Conclusion This study is the first to demonstrate the use of wrist actigraphy-based estimates of circadian phase as a clinically useful and valid alternative to in-lab measurement of DLMO in fixed night shift workers. Future research should explore how additional predictors may impact accuracy.

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Circadian misalignment increases mood vulnerability in simulated shift work

Scientific Reports ◽

10.1038/s41598-020-75245-9 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Sarah L. Chellappa ◽

Christopher J. Morris ◽

Frank A. J. L. Scheer

Keyword(s):

Shift Work ◽

Night Shift ◽

Well Being ◽

Continuous Exposure ◽

Shift Workers ◽

Circadian Misalignment ◽

Alignment Condition ◽

Increased Risk ◽

Mood Effects ◽

Alignment Interaction

Abstract Night shift work can associate with an increased risk for depression. As night workers experience a ‘misalignment’ between their circadian system and daily sleep–wake behaviors, with negative health consequences, we investigated whether exposure to circadian misalignment underpins mood vulnerability in simulated shift work. We performed randomized within-subject crossover laboratory studies in non-shift workers and shift workers. Simulated night shifts were used to induce a misalignment between the endogenous circadian pacemaker and sleep/wake cycles (circadian misalignment), while environmental conditions and food intake were controlled. Circadian misalignment adversely impacted emotional state, such that mood and well-being levels were significantly decreased throughout 4 days of continuous exposure to circadian misalignment in non-shift workers, as compared to when they were under circadian alignment (interaction of “circadian alignment condition” vs. “day”, mood: p < 0.001; well-being: p < 0.001; adjusted p-values). Similarly, in shift workers, mood and well-being levels were significantly reduced throughout days of misalignment, as compared to circadian alignment (interaction of “circadian alignment condition” vs. “day”, mood: p = 0.002; well-being: p = 0.002; adjusted p-values). Our findings indicate that circadian misalignment is an important biological component for mood vulnerability, and that individuals who engage in shift work are susceptible to its deleterious mood effects.

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Objective Food Intake in Night and Day Shift Workers: A Laboratory Study

Clocks & Sleep ◽

10.3390/clockssleep1010005 ◽

2018 ◽

Vol 1 (1) ◽

pp. 42-49 ◽

Cited By ~ 8

Author(s):

Yichi Chen ◽

Shaza Lauren ◽

Bernard P. Chang ◽

Ari Shechter

Keyword(s):

Food Intake ◽

Sleep Duration ◽

Shift Work ◽

Test Meal ◽

Food Choice ◽

Night Shift ◽

Overweight And Obesity ◽

Shift Workers ◽

Sleep Episode ◽

Night And Day

Night shift work is associated with risk of overweight and obesity. In night shift workers, short sleep duration combined with circadian misalignment may contribute to altered food intake regulation, favoring positive energy balance and weight gain. Prior work investigating food intake in shift workers has suffered methodologically due to reliance on subjective self-report for dietary assessment. No study has yet been done to examine the impact of night shift work on food intake in real-life shift workers using objective measures. Female day (n = 12) and night (n = 12) shift workers from a hospital setting participated in a laboratory-based objective food intake assessment. Participants entered the laboratory in the fasted state after awakening from the sleep episode following a final work shift, and underwent an ad libitum 14-item test meal buffet to objectively quantify food choice/intake. Sleep duration (measured via wrist-accelerometry) during the sleep episode before laboratory assessment was significantly longer in day vs. night workers (373.9 ± 127.5 vs. 260.6 ± 102.9 min, p = 0.03). No significant group difference was observed in calories consumed during the test meal (943.08 ± 469.55 vs. 878.58 ± 442.68 kcal, p = 0.74). When expressed as percent of energy consumed, day workers had higher protein consumption vs. night workers (16.03 ± 5.69 vs. 11.82 ± 4.05%; p = 0.05). To our knowledge, this is the first laboratory-based behavioral assessment of food choice/intake in actual night and day shift workers. Although not studied here, work by others has linked protein intake to satiety. This may be a potential pathway placing shift workers at risk for overweight and obesity.

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Shift Work and Cognitive Flexibility: Decomposing Task Performance

Journal of Biological Rhythms ◽

10.1177/0748730417699309 ◽

2017 ◽

Vol 32 (2) ◽

pp. 143-153 ◽

Cited By ~ 12

Author(s):

Philip Cheng ◽

Gabriel Tallent ◽

Thomas John Bender ◽

Kieulinh Michelle Tran ◽

Christopher L. Drake

Keyword(s):

Cognitive Functioning ◽

Task Performance ◽

Shift Work ◽

Cognitive Flexibility ◽

Switch Cost ◽

Night Shift ◽

Cognitive Effort ◽

Future Research ◽

Shift Workers ◽

Circadian Phase

Deficits in cognitive functioning associated with shift work are particularly relevant to occupational performance; however, few studies have examined how cognitive functioning is associated with specific components of shift work. This observational study examined how circadian phase, nocturnal sleepiness, and daytime insomnia in a sample of shift workers ( N = 30) were associated with cognitive flexibility during the night shift. Cognitive flexibility was measured using a computerized task-switching paradigm, which produces 2 indexes of flexibility: switch cost and set inhibition. Switch cost represents the additional cognitive effort required in switching to a different task and can impact performance when multitasking is involved. Set inhibition is the efficiency in returning to previously completed tasks and represents the degree of cognitive perseveration, which can lead to reduced accuracy. Circadian phase was measured via melatonin assays, nocturnal sleepiness was assessed using the Multiple Sleep Latency Test, and daytime insomnia was assessed using the Insomnia Severity Index. Results indicated that those with an earlier circadian phase, insomnia, and sleepiness exhibited reduced cognitive flexibility; however, specific components of cognitive flexibility were differentially associated with circadian phase, insomnia, and sleepiness. Individuals with an earlier circadian phase (thus more misaligned to the night shift) exhibited larger switch costs, which was also associated with reduced task efficiency. Shift workers with more daytime insomnia demonstrated difficulties with cognitive inhibition, whereas nocturnal sleepiness was associated with difficulties in reactivating previous tasks. Deficits in set inhibition were also related to reduced accuracy and increased perseverative errors. Together, this study indicates that task performance deficits in shift work are complex and are variably impacted by different mechanisms. Future research may examine phenotypic differences in shift work and the associated consequences. Results also suggest that fatigue risk management strategies may benefit from increased scope and specificity in assessment of sleep, sleepiness, and circadian rhythms in shift workers.

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O4A.4 The relationship between shift work and sleep disturbance in hospital workers

Occupational and Environmental Medicine ◽

10.1136/oem-2019-epi.88 ◽

2019 ◽

Vol 76 (Suppl 1) ◽

pp. A33.1-A33

Author(s):

Dong-Hee Koh ◽

Ju-Hyun Park ◽

Seo-Hyun Yoon ◽

Hyun-Joo Kim

Keyword(s):

Sleep Disturbance ◽

Shift Work ◽

Night Shift ◽

Sleep Onset ◽

Consecutive Night ◽

Hospital Workers ◽

Sleep Maintenance ◽

Sleep Questionnaires ◽

The Relationship ◽

Night Shifts

IntroductionMany hospital workers suffer from sleep disturbance due to shift work. The best way to mitigate the problem would be reducing night shift. However, that is commonly impossible in reality. Thus, we aimed to examine the factors associated with sleep disturbance and suggest better-rotating schedules for hospital workers.MethodsWe used sleep questionnaires asking sleep disturbance including sleep onset and maintenance problems for measuring health outcomes. Also, We obtained a duty schedule of the workers for assessing exposure. We examined the effect of the pattern of shift schedule and amount of night shifts on sleep disturbance.ResultsA total of 590 workers participated in this study. Female (95%) 3-rotating shift (92%) workers dominated. For workshift pattern, two consecutive night shifts increased the risk of sleep maintenance problem significantly. For the amount of night shift, two or more night shifts per week increased the risk of sleep onset problem significantly.ConclusionOur results suggest that avoding consecutive night shifts and restricting night shift to one time per week would be helpful to prevent sleep disturbance in hospital workers.

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Social jetlag and sleep debts are altered in different rosters of night shift work

PLoS ONE ◽

10.1371/journal.pone.0262049 ◽

2022 ◽

Vol 17 (1) ◽

pp. e0262049

Author(s):

Swaantje Casjens ◽

Frank Brenscheidt ◽

Anita Tisch ◽

Beate Beermann ◽

Thomas Brüning ◽

...

Keyword(s):

Sleep Quality ◽

Sleep Deprivation ◽

Sleep Duration ◽

Shift Work ◽

Night Shift ◽

Shift Workers ◽

Social Jetlag ◽

Sleep Debt ◽

The Impact ◽

Night Shifts

Background Night and shift work are suspected to cause various adverse effects on health and sleep. Sleep deprivation through shift work is assumed to be compensated on free days. So far it is not clear how different shift systems and shift lengths affect sleep structure on work and free days. Especially working night shifts disrupts the circadian rhythm but also extended working hours (12h) might affect sleep characteristics. Hitherto, the magnitude of sleep debt, social jetlag, and Locomotor Inactivity During Sleep (LIDS) in different shift systems is unknown. Methods Here, we investigated the impact of five different shift rosters on sleep in 129 industrial workers from Germany. Permanent night work with multiple shift systems with and without night shifts and with different shift lengths were compared. Wrist-activity was monitored over 28 days revealing sleep on- and offsets as well as LIDS as proxy for sleep quality. Overall, 3,865 sleep bouts comprising 22,310 hours of sleep were examined. Results The mean daily age-adjusted sleep duration (including naps) was 6:43h and did not differ between shift workers of different rosters. However, sleep duration on workdays was particularly low in rotational shift systems with 12h-shifts (5:00h), while overall sleep debt was highest. Shift workers showed a median absolute social jetlag of 3:03h, which differed considerably between shift types and rosters (p<0.0001). Permanent night workers had the highest social jetlag (5:08h) and latest mid-sleeps on workdays and free days. Sleep quality was reduced in permanent night shift workers compared with shift workers in other rosters and differed between daytime and nighttime sleep. Conclusions Shift work leads to partial sleep deprivation, which particularly affects workers in 12h-shifts and permanent night shifts. Working these shifts resulted in higher sleep debts and larger absolute social jetlag whereas sleep quality was especially reduced in permanent night shift workers compared with shift workers of other rosters.

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0253 Eating Behaviors, Physical Activity, and Sleep in Shift Workers: Results from a Combined Field and Laboratory Study

SLEEP ◽

10.1093/sleep/zsaa056.251 ◽

2020 ◽

Vol 43 (Supplement_1) ◽

pp. A96-A97

Author(s):

Y Chen ◽

S Lauren ◽

A Shechter

Keyword(s):

Physical Activity ◽

Sleep Duration ◽

Shift Work ◽

Test Meal ◽

Food Choice ◽

Protein Intake ◽

Real Life ◽

Shift Workers ◽

Circadian Misalignment ◽

Dietary Recall

Abstract Introduction In shift workers, short sleep duration combined with circadian misalignment may affect behaviors that impact regulation of energy balance and metabolism. We conducted a combined field-and-laboratory study to determine how real-life shift work affects diet, physical activity, and sleep via objective and self-report measures. Methods Participants were day (n=12) and night (n=12) shift workers from an urban hospital setting (nurses and technicians, all female). During the field portion of the study, participants wore a wrist-mounted accelerometer to track sleep and physical activity during their series of shifts, and completed a computer-assisted 24-hour dietary recall. After awakening from the sleep episode following the final work shift, participants entered the laboratory in the fasted state and underwent an ad libitum 14-item test-meal buffet to objectively quantify food choice and intake. Results Sleep duration was significantly shorter and worse quality in night vs. day workers. Physical activity levels were not different between groups. Based on 24-h dietary recall, night vs. day workers consumed less protein (65.9 ± 39.0 vs. 87.2 ± 40.7 g, p=0.01) and fiber (12.5 ± 6.0 vs. 16.9 ± 6.2 g, p=0.01), but did not differ in daily intakes of calories, fat, or carbohydrate. Night vs. day workers reported a longer daily window of eating duration (14.2 ± 3.8 vs. 12.0 ± 1.5 h, p=0.02). In the lab test-meal, there were no group differences in total calories consumed. When expressed as percent of calories consumed, night vs. day workers had lower protein intake (11.82 ± 4.05 vs. 16.03 ± 5.69 %; p=0.05). Conclusion To our knowledge, this was the first study to include a laboratory-based behavioral assessment of food choice/intake in real-life night and day shift workers using objective measures. We did not assess measures of circadian phase so can only assume that circadian misalignment, in addition to the disturbances in sleep duration and quality, contributes to findings. Changes to dietary patterns in night vs. day workers (namely, reduced protein intake which may affect satiety, and prolonged daily eating duration window) may present potential pathways by which night shift work contributes to risk for overweight and obesity. Support UL1TR000040

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Postprandial hormone and metabolic responses amongst shift workers in Antarctica

Journal of Endocrinology ◽

10.1677/joe.0.1710557 ◽

2001 ◽

Vol 171 (3) ◽

pp. 557-564 ◽

Cited By ~ 116

Author(s):

J Lund ◽

J Arendt ◽

SM Hampton ◽

J English ◽

LM Morgan

Keyword(s):

Shift Work ◽

Venous Blood ◽

Night Shift ◽

Postprandial Glucose ◽

Metabolic Responses ◽

Cvd Risk ◽

Night Time ◽

Shift Workers ◽

Circadian Phase ◽

The Uk

The circadian rhythms of many night-shift workers are maladapted to their imposed behavioural schedule, and this factor may be implicated in the increased occurrence of cardiovascular disease (CVD) reported in shift workers. One way in which CVD risk could be mediated is through inappropriate hormonal and metabolic responses to meals. This study investigated the responses to standard meals at different circadian times in a group of night-shift workers on a British Antarctic Survey station at Halley Bay (75 degrees S) in Antarctica. Twelve healthy subjects (ten men and two women) were recruited. Their postprandial hormone and metabolic responses to an identical mixed test meal of 3330 kJ were measured on three occasions: (i) during daytime on a normal working day, (ii) during night-time at the beginning of a period of night-shift work, and (iii) during the daytime on return from night working to daytime working. Venous blood was taken for 9 h after the meal for the measurement of glucose, insulin, triacylglycerol (TAG) and non-esterified fatty acids. Urine was collected 4-hourly (longer during sleep) on each test day for assessment of the circadian phase via 6-sulphatoxymelatonin (aMT6s) assay. During normal daytime working, aMT6s acrophase was delayed (7.7+/-1.0 h (s.e.m.)) compared with that previously found in temperate zones in a comparable age-group. During the night shift a further delay was evident (11.8+/-1.9 h) and subjects' acrophases remained delayed 2 days after return to daytime working (12.4+/-1.8 h). Integrated postprandial glucose, insulin and TAG responses were significantly elevated during the night shift compared with normal daytime working. Two days after their return to daytime working, subjects' postprandial glucose and insulin responses had returned to pre-shift levels; however, integrated TAG levels remained significantly elevated. These results are very similar to those previously found in simulated night-shift conditions; it is the first time such changes have been reported in real shift workers in field conditions. They provide evidence that the abnormal metabolic responses to meals taken at night during unadapted night shifts are due, at least in part, to a relative insulin resistance, which could contribute to the documented cardiovascular morbidity associated with shift work. When applied to the 20% of the UK workforce currently employed on shift work, these findings have major significance from an occupational health perspective.

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Disturbances of Autonomic Regulation of Cardiovascular System at Different Working Regimes with Night Shifts

Kardiologiia ◽

10.18087/cardio.2020.9.n1134 ◽

2020 ◽

Vol 60 (9) ◽

pp. 62-67

Author(s):

Yu. A. Merkulov ◽

A. A. Pyatkov ◽

S. G. Gorokhova ◽

D. M. Merkulova ◽

O. Yu. Atkov

Keyword(s):

Shift Work ◽

Spectral Characteristics ◽

Night Shift ◽

Autonomic Regulation ◽

Total Power ◽

Orthostatic Test ◽

Heart Rhythm Variability ◽

Shift Workers ◽

Rotating Shift Work ◽

Night Shifts

Aim To study temporal and spectral characteristics of heart rhythm variability (HRV) in night shift workers.Materials and methods Along with traditional risk factors, conditions of labor contribute to development of cardiovascular morbidity, including night shift work, which can be associated with disorders of the autonomic regulation detected by analysis of HRV. This study included 100 healthy men. 74 of them were engaged in shift work, including 53 men with rotating shift work, 21 men with fixed night shifts, and 26 men with day-time work. HRV was analyzed by data of 5-min electrocardiogram recording (background recording and orthostatic test).Results Night-shift workers had decreases in total power of regulation (ТР, SDNN) and in the parasympathetic branch (HF, pNN50). Rotating night-shift workers displayed significant decreases in SDNN and pNN50 and pronounced changes in the VLF / LF / HF ratio in the orthostatic test.Conclusion In work with night shifts, the type of autonomic regulation differs from the “standard” functioning of the autonomic nervous system (ANS). This study showed different effects of night work regimens on HRV indexes. With the rotating shift work, the ANS dysregulation was more profound and was evident by a significant decrease in the ANS total tone and parasympathetic activity (SDNN, pNN50) compared to night shifts with fixed working hours. The excessive weakening of the parasympathetic component in the passive orthostatic test can be considered as an early marker for ANS maladaptation.

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