Night Shift Work Research Articles

Research progress on the relation and related mechanism of night shift work and cardiovascular disease

Cardiovascular disease is a class of diseases involving the heart or blood vessels, which accounts for about one-third of all deaths worldwide each year. Unhealthy diet, lack of physical activity, smoking and excessive alcohol consumption are all risk factors for cardiovascular disease. With the increasing number of night shift workers, the number of patients with cardiovascular disease has increased, and night shift work has gradually become a risk factor of cardiovascular disease. At present, the mechanism of cardiovascular disease caused by night shift work is still unclear. This review summarizes the relationship between night shift work and cardiovascular disease and its related biochemical indicators, and discusses the research on related mechanisms.

Are Short Duration Naps Better than Long Duration Naps for Mitigating Sleep Inertia? Brief Report of a Randomized Crossover Trial of Simulated Night Shift Work

Objective We sought to test the effects of different duration naps on post-nap cognitive performance during simulated night shifts. Methods We used a randomized laboratory-based crossover trial design with simulated 12-hr night shifts and each participant completing three conditions of 72 hrs each (Clinicaltrials.gov; registration # NCT04469803). The three conditions tested included no-nap, a 30-min nap opportunity, and a 2-hr nap opportunity. Naps occurred at 02:00 hrs. Cognitive performance was assessed with the Brief 3-min Psychomotor Vigilance Test (PVT-B). Four PVT-B measures include: reaction time (RT in milliseconds (ms)), lapses (RT > 355 ms), false starts (reactions before stimulus or RT <100 ms), and speed (1,000/RT). The PVT-B was performed at the start of the simulated night shift (19:00), end of shift (07:00), pre-nap (02:00), and at 0 mins, 10 mins, 20 mins, and 30 mins following the 30-min and 2-hr nap conditions. Simultaneously, participants reported subjective ratings of fatigue and other constructs. Results Twenty-eight (15 female), mostly certified emergency medical technicians or paramedics, consented to participate. For all three conditions, looking within condition, PVT-B lapse performance at the end of the 12-hr simulated night shift (at 07:00) was poorer compared to shift start (p < 0.05). Performance on PVT-B speed, RT, and false starts were poorer at shift end than shift start for the no-nap and 30-min nap conditions (p < 0.05), but not for the 2-hr nap condition (p > 0.05). Compared to pre-nap measures, performance on the PVT-B assessed at 0 mins post-nap showed significant performance declines for lapses and speed for both the 30-min and 2-hr nap conditions (p < 0.05), but not at 10, 20, or 30 mins post-nap. After waking from the 2-hr on-shift nap opportunity (at 0 mins), participants rated sleepiness, difficulty with concentration, and alertness poorer than pre-nap (p < 0.05). Participants in the 30-min nap condition rated alertness poorer immediately after the nap (at 0 mins) compared to pre-nap (p < 0.05) Conclusions While sleep inertia was detectable immediately following short 30-min and long 2-hr nap opportunities during simulated night shift work, deficits in cognitive performance and subjective ratings quickly dissipated and were not detectable at 10–30 mins post-nap.

Independent, modified, and interacting effects of long-term noise, extremely low-frequency electromagnetic fields, and shift work exposures on liver enzymes

To quantify long-term independent, modified, and interacting effects of noise, extremely low-frequency electromagnetic fields (ELF-EMFs), and shift work exposures on liver enzymes, a four-year repeated measures study was performed among male workers in a thermal power plant industry from 2016 to 2020. The 8-h equivalent sound pressure levels (Leq) were measured at weighting channels of Z, A, and C for octave-band frequencies. The 8-h time-weighted average of ELF-EMFs levels was measured for each participant. Shift work schedule was determined based on job titles, including 3-rotating night shift work and fixed day shift work schedules. The fasting blood samples were taken to determine liver enzymes (AST, Aspartate transaminase; ALT, Alanine transaminase). The percentage change (PC) and 95% confidence interval (CI) of AST and ALT enzymes were estimated by the different bootstrapped-mixed-effects linear regression models. Per 10-dB noise increase, we found a significantly higher PC (95% CI) of AST and ALT (only LAeq) levels in all regression models with the highest changes for LAeq. For the octave-band noise analysis, there was an upward trend from 31.5 Hz to 1 kHz frequencies and a downward trend from 1 to 8 kHz frequencies. Per 1 mG ELF-EMFs increase, we observed a significantly higher PC (95% CI) of AST and ALT enzymes in the main adjusted and the main adjusted + shift work models. The 3-rotating night than fixed day shift workers had a significant PC in the unadjusted model for AST enzyme and the fully adjusted and the main adjusted + ELF-EMFs models for ALT enzyme. Significant negative two-way or/and three-way interaction effects among the noise, ELF-EMFs, and shift work were observed for both AST and ALT enzymes. Our findings indicated long-term noise, ELF-EMFs, and 3-rotating night shift work exposures may be significantly associated with changes in the levels of liver enzymes.

Working conditions, medical support and morbidity of stress-related neurotic disorders among Russian Railways employees

Introduction. Shift work, as the main stress factor, leads to the development of desynchronosis and other neurotic diseases. The production necessity with such a work schedule requires increased provision of mental health specialists.&#x0D; The study aims to analyze the long-term dynamics of morbidity of employees of JSC "Russian Railways" with neurotic diseases associated with stress and somatoform disorders, depending on the intensity of work, availability of specialists responsible for psychoprophylactic work.&#x0D; Materials and methods. Scientists investigated the working conditions and their influence on the functional state of employees of JSC "Russian Railways". The authors have carried out a retrospective analysis of information from the Unified Medical Information and Analytical System from 2012–2021 for JSC "Russian Railways" and the Ministry of Health of Russian Federation. The analysis of morbidity in mental pathology included nosological units assigned by ICD-10 to F40–F48.&#x0D; Results. Work in the system of JSC "Russian Railways" is associated with the impact of a complex of unfavorable production factors, the key of which are psycho-emotional stress and shift work schedule — work in night shifts. Railway transport workers face various stressful factors on a daily basis, such as: desynchronosis due to shift work schedules, waiting for an emergency situation with a "system call", "broken" schedules, and related difficulties. The psychogenic factor, which is an etiological factor in the occurrence of neurotic disorders, constantly affects railway transport workers. Based on the analyzed data, it can be assumed that professionally conditioned factors of the working environment contribute to the formation of occupational stress and the formation of neurotic disorders among this category of workers. There is a connection with the growth of neurotic diseases and the annual trend of declining positions of psychologists and psychotherapists in the system of JSC "Russian Railways". There was a significant increase in the incidence of railway transport workers (p=0.043) and a decrease in specialists associated with the prevention of neuropsychiatric diseases for ten years (p=0.0001).&#x0D; Limitations. Limitations are presented in the form of a small sample of employees of JSC "Russian Railways", insufficient depth of study of materials of foreign literature on the issue under study.&#x0D; Conclusions. Neurotic disorders in persons who are under dispensary supervision in the system of JSC "Russian Railways" have a pronounced, statistically significant growth trend. There is a significant decrease in the number of medical specialists engaged in the diagnosis, treatment and prevention of psychogenic diseases of workers. Based on the results of the study, we have revealed a link between the growth of neurotic diseases of railway transport workers and the annual decline trend of psychologists and psychotherapists in JSC "Russian Railways".&#x0D; Ethics. This study was carried out in accordance with the rules of good clinical practice and the Helsinki Declaration and did not require the conclusion of the ethics committee.

Pediatric private practice in the Nord-Pas-de-Calais region: Demographics, organization, and challenges

While the needs for pediatric care are increasing and becoming more diverse, pediatric private practice in France is encountering difficulties linked to a growing medical demographic deficit. The objective of this study was to give an overview of pediatric private practice in the Nord-Pas-de-Calais region and to describe the main challenges encountered. MethodsFor this descriptive observational survey, private practice pediatricians in the Nord-Pas-de-Calais region filled out an online questionnaire between April 2019 and October 2020. ResultsThe response rate was 64%. Most respondents practiced in an urban area (87%) and shared the practice with other physicians (59%). A majority (85%) had previously worked in hospital; 65% reported training in a subspecialty. Overall, 48% had other professional activities; 28% worked night shifts and 96% accepted urgent requests for consultations. A total of 33% reported having difficulties contacting specialists for consults, and 46% had difficulties in obtaining written reports of their patients’ hospitalizations. All respondents participated in a form of ongoing medical education. The main difficulties were: lack of information about how to found a private practice (68%), lack of personal time (61%), balance between medical and administrative work (59%), and an excess of patients to care for (57%). The main satisfactions were: trusting relationships with patients (98%), freedom in their choice of practice (85%), and the diversity of problems and situations encountered (68%). ConclusionOur study underlines that private practice pediatricians are involved in healthcare provision, in particular regarding ongoing medical training, subspecialties, and continuity of care. It also highlights the problems encountered and the possible improvements: developing better communication between private practice and hospitals, reinforcing training during residency, and highlighting the importance and complementarity of private practice in children's healthcare.

Nurses' napping practices and their effects on sleepiness, fatigue, well-being, and quality of nursing care

Background &amp; Aim: Napping is one of the evidence-based countermeasures to fatigue and decreased alertness during night shift work. We aimed to understand night shift nurses' napping practices and study the effectiveness of different nap lengths on sleepiness, fatigue, well-being, and the quality of nursing care.&#x0D; Methods &amp; Materials: A comparative descriptive design was used. Data were self-reported by 305 nurses using the Questionnaire on Night Shift Napping Practices, the Karolinska Sleepiness Scale, the Fatigue Visual Analog Scale, the Everyday Feeling Questionnaire, and the Quality of Nursing Care Questionnaire. Data collection was done over 4 months between August and November 2022. Frequency tables, Mean, and standard deviation were used to describe data, and One-way analysis of variance (ANOVA) was used for means comparisons.&#x0D; Results: About 40% of the nurses reported that they took naps during their night shifts. The majority (82.92%) reported that they napped for more than 45 minutes (N= 305). Napping was found to significantly reduce sleepiness (P= 0.002) and fatigue (P= 0.001) and improve the quality of nursing care (P= 0.03). The group who napped for more than 45 minutes reported significantly reduced levels of sleepiness (P= 0.02) and fatigue (P= 0.01) when compared to the group who either didn’t nap or napped for less than 45 minutes.&#x0D; Conclusion: This study suggests that implementing nap interventions for nurses on night shift can be an effective method to reduce sleepiness and fatigue, and improve patient care.

24 HOURS CHRONOMICS OF AMBULATORY BLOOD PRESSURE/HEART RATE IN TERMS OF ACROPHASE &amp; HYPERBARIC INDEX IN NIGHT SHIFT NURSING PROFESSIONALS: RISK FOR CARDIOVASCULAR DISEASES

Objective: This study was aimed to investigate the effect of Light at night and Rotating night shift as risk factor for cardiovascular diseases. 24 hours chronomics of BP/HR in terms of Double amplitude, Acrophase and Hyperbaric index and its relation with circadian rhythm of salivary cortisol and 6 sulfatoxy melatonin levels in night shift nursing professional. Design and method: 56 night shift nurses, aged 20 to 40 years, performing day and night shift duties were recruited from the Trauma Center, KGMU, India, and 56 age sex matched actual day workers were also enrolled as controls. During their night and day shift duties, BP/HR were recorded by Ambulatory Blood Pressure Monitoring (ABPM) along with circadian pattern of cortisol in saliva, metalonin in urine also tested. Results: Highly significant difference was found in double amplitude (2DA) of among between night (23.10 ± 14.68) and day shift (34.27 ± 16.44) (p &lt; 0.0005). In night shift, hyperbaric index (HBI) of mean SBP was found to be increased at 00 to 03 am (midnight) while during day shift, peak was found at 06 to 09 am. HBI of mean HR was found to be increased at 18 to 21 pm during night shift while in controls, peak was found at 09 to 12 &amp; again 15 to 18 pm of SBP, DBP &amp; HR. Alterations in Acrophase of BP/HR were very common among night shift workers and Ecphasia was found in few nights shift workers. Difference was found in night cortisol levels among night (4.08 ± 3.28) vs day shift (2.62 ± 2.37), while in comparison to night shift or day shift with controls (1.82 ± 1.18) these difference was significant (p &lt; 0.05). Conclusions: Alteration in morning melatonin and Night cortisol level were found during night shift. Reverse pattern of Acrophase and HBI of BP/HR along with salivary cortisol during night shift represents desynchronization. It indicates that the circadian rhythm was disrupted during night shift and incomplete recovery occurs during day shift. It may leads to future cardio vascular diseases risk.

Obesity, Chronic Stress, and Stress Reduction.

The obesity epidemic is caused by the misalignment between human biology and the modern food environment, which has led to unhealthy eating patterns and behaviors and an increase in metabolic diseases. This has been caused by the shift from a "leptogenic" to an "obesogenic" food environment, characterized by the availability of unhealthy food and the ability to eat at any time of day due to advances in technology. Binge Eating Disorder (BED) is the most commonly diagnosed eating disorder, characterized by recurrent episodes of binge eating and a sense of loss of control over eating, and is treated with cognitive-behavioral therapy-enhanced (CBT-E). Shift work, especially night shift work, can disrupt the body's natural circadian rhythms and increase the risk of obesity and other negative health consequences, such as cardiovascular disease and metabolic syndrome. One dietary approach to address circadian dysregulation is time-restricted eating (TRE), which involves restricting food intake to specific periods of the day to synchronize the body's internal clock with the external environment. TRE has been found to cause modest weight loss and improve metabolic outcomes such as insulin sensitivity and blood pressure, but the extent to which it is beneficial may depend on adherence and other factors such as caloric restriction.

0288 Multidimensional Sleep Health and Cognitive Function in Retired Night Shift Workers and Retired Day Workers

Abstract Introduction Night shift work is associated with compromised cognitive function, and with chronic exposure, may place shift workers at elevated risk for dementia. Given that former night shift workers experienced prior long-term sleep and circadian rhythm disruption, their sleep in retirement—after returning to a daytime schedule—may be particularly salient for cognitive function. This study examined associations between multidimensional sleep health and neurocognitive function among retired night shift workers and retired day workers. Methods Participants (N = 61; mean age: 67.9 +/- 4.7 years; 61% females; 13% non-Hispanic White) were 31 RDW and 30 RNSW equated on age, sex, race/ethnicity, premorbid IQ, and years in retirement. Multidimensional sleep health was quantified using wrist actigraphy measures of sleep efficiency, timing, duration, and regularity, and diary measures of alertness and satisfaction. Each component was dichotomized and summed to create a composite score (0-6); higher values indicated better sleep health. Participants completed a neurocognitive battery assessing six cognitive domains (language, visuospatial ability, attention, immediate and delayed memory, executive function) and self-reported cognitive function. Linear regression models tested associations of multidimensional sleep health and its individual components with cognitive domains in each group, adjusting for age, sex, and education. Results Retired night shift workers and retired day workers did not differ on multidimensional sleep health or its individual components. Among retired night shift workers, poorer multidimensional sleep health was associated with poorer self-reported global cognitive function (beta = 0.51, p = .018), and more irregular sleep timing was associated with poorer self-reported memory (beta = 0.41, p = .054). Multidimensional sleep health and its individual components were unrelated to cognitive function in retired day workers. Conclusion Retired night shift workers may be cognitively vulnerable to poor sleep health in retirement, possibly due to a history of long-term sleep and circadian rhythm disruption while working. Given that self-reported cognitive difficulties often precede more objective cognitive changes, future research should determine whether associations of sleep health with cognitive function are found in more objective cognitive measures as retired night shift workers age. Support (if any) R01AG047139, R01AG047139-S1, K01AG075171

0617 Tracking circadian phase for personalized schedules: A precise medical approach to reduce circadian misalignment in shift workers

Abstract Introduction Night shift workers experience symptoms of excessive sleepiness and insomnia due to misalignment between the work schedule and their circadian clock. Circadian misalignment can be corrected using exposure to bright light delivered in accordance with a phase response curve. Given the high variability of circadian phase in night shift workers, using a one-schedule-fits-all approach to light therapy might result in significant error (e.g., phase shifts in the wrong direction). Instead, a personalized light exposure schedule should result in more consistent and precise phase shifts. This randomized controlled trial compared personalized and non-personalized light schedules in shifting circadian phase in night shift workers. Methods Individuals with shift work disorder (ICSD-3 diagnostic criteria) were randomized into two conditions: personalized light therapy, or non-personalized light therapy control. Personalized light schedules were based on estimates of dim light melatonin onset (DLMO) derived from mathematical modeling of activity data collected via an Apple Watch. Estimates were confirmed with in-lab DLMO. Light schedules were delivered through a mobile app (SHIFT) that updated in accordance with real-time estimates of DLMO. Participants were provided a light box as a source of bright light at night and light blocking glasses. Phase shifts were determined based on in-lab DLMO measured before and after treatment. Results Those who received personalized light therapy treatment achieved a larger phase delay (Mean = 7.37 hours, SD = 3.03 hours) compared to those in the non-personalized light therapy control group (Mean = 0.84 hours, SD = 3.46 hours), t(5) = 2.501, p = 0.05. Conclusion Preliminary results suggest that personalized light therapy may be a more effective treatment to correct circadian misalignment in night shift workers by delivering treatment according to each individual’s unique circadian phase. This has implications for improving the symptoms of shift work disorder and quality of life for this population. Support (if any) Support for this study was provided from the National Institute of Health R41HL163783 and the American Academy of Sleep Medicine Foundation (245-SR-21) awarded to Dr. Philip Cheng.

0007 Later circadian phase and increased sleep variability are associated with overnight blood pressure dipping in chronic shiftworkers

Abstract Introduction Nighttime shift work is associated with adverse cardiovascular outcomes, including hypertension. Increased sleep variability and circadian disruption may increase sympathetic activity and waking blood pressure (BP), potentially constraining typical BP reductions during overnight sleep. However, the relationships between circadian phase, sleep variability, and overnight BP reduction (dipping) among day vs. chronic nightshift workers is unknown. Methods Ambulatory BP was monitored for up to 48-hours among 10 dayshift (mean□SD; age 33.1□7.0y; BMI 26.3□5.4 kg/m2) and 10 chronic (9.3□6.8y of shiftwork) nightshift workers (age 32.7□9.1y; BMI 27.9□7.6 kg/m2). Overnight BP dipping was calculated from the sleeping/waking systolic BP ratio. Variability in sleep timing was defined as the SD of self-reported daily-diary sleep onset across 1-week. Circadian phase was determined by salivary dim-light melatonin onset (DLMO; 3pg/ml threshold). Differences between groups were assessed using independent t-tests and linear mixed-effects models with group and time-from-sleep-onset or circadian phase as fixed-effects, and participant as a random effect. Relationships between overnight BP dipping and DLMO, sleep onset timing variability, and phase angle of entrainment (DLMO to sleep onset during ambulatory BP) were assessed using Pearson correlation analyses. Results Chronic nightshift workers had reduced overnight BP dipping (-9.3□1.5 % vs -13.4□4.4 %; p=0.04), later DLMO timing (21:08□0:53 vs 19:21□1:02; p=0.001), smaller phase angle of entrainment (3.7□1.0 h vs 5.0□0.90 h; p=0.02), and greater variability in sleep onset timing (3.2□1.5 h vs 0.87□0.34 h; p&amp;lt; 0.001). Significant group effects for higher systolic BP across circadian phase and time from sleep onset in the nightshift group were observed compared to dayshift (both p&amp;lt; 0.05). DLMO (r=0.49; p=0.04) and phase angle of entrainment (r=0.53; p=0.02) were associated with overnight BP dip magnitude (later circadian phase correlated with less dipping). Sleep onset timing variability was negatively correlated with magnitude of overnight BP dipping in nightshift (r= -0.76; p=0.04) but not dayshift workers (r=0.26; p=0.61). Conclusion Attenuated overnight BP dipping among chronic nightshift workers may be indicative of increased cardiovascular risk. Chronic circadian disruptions (i.e., smaller phase angle of entrainment) as a function of higher sleep variability among nightshift workers may mechanistically contribute to poorer health outcomes compared to dayshift workers. Support (if any) R01HL105495, K01HL146992

0003 Sleep and Circadian Disruption Induced by Simulated Night Shift Work Impair Cardiometabolic Outcomes in Healthy Adults

Abstract Introduction People who work evening, night or rotating shifts make up 20% of the US workforce and have a heightened risk for Type 2 diabetes (T2D) and cardiovascular disease (CVD) compared to people who work days, possibly due to repeated bouts of sleep and circadian disruption. However, the mechanism(s) by which sleep and circadian disruption impair cardiometabolic health are unclear. We therefore investigated the impact of acute circadian misalignment on factors related to cardiometabolic health including interstitial glucose concentration, glucose tolerance, resting systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). Methods Ten healthy adults (6F, 25.0±4.5y, BMI: 22.0±2.2kg/m2; mean±SD) participated in an ongoing 6d inpatient simulated night shift protocol to induce sleep and circadian disruption. Participants lived at the Sleep and Metabolism Laboratory for 2d to simulate day shift work followed by 2d of simulated night shift work. Continuous interstitial glucose monitoring was conducted throughout the study (FreeStyle Libre Pro; Abbott, Alameda, CA, USA). BP and HR were assessed 30 minutes after waketime (Omron HEM-FL31; Omron Healthcare, Kyoto, JP) followed by an oral glucose tolerance tests (OGTT) conducted 1.5h after waketime in both conditions. Results Simulated night shift work was associated with significantly higher interstitial glucose area under the curve (AUC) in response to an identical first meal after waking (18,299±1412 v 14,606±2035 [mg/dl]*min; p=0.009; mean±SEM) as well as plasma glucose AUC during the OGTT (23,239±2574 v 18,776±1832; p=0.002) compared to simulated day work. Furthermore, simulated night shift work was associated with a significant increase in resting DBP (75±3 v 66±2; p=0.017) compared to day work. No changes were observed in resting SBP (p=0.40) or HR (p=0.11) between conditions. Conclusion Sleep and circadian disruption induced by simulated night shift work appear to impair markers of cardiometabolic health, even in healthy, lean adults. Night shift work is largely unavoidable in modern society, thus is it critical to identify strategies or countermeasures to prevent the impact of circadian misalignment on T2D and CVD risk in a large portion of the population. Support (if any) This project was supported in part by R01DK125653 &amp; F31HL165883.

0005 A circadian-informed lighting intervention markedly improves vigilance in a simulated night shift setting

Abstract Introduction Due to misalignment between circadian timing and the work/rest schedule, cognitive performance during night shift-work is often poor. This study tested a circadian-informed lighting strategy designed to improve on-shift cognitive performance through alerting effects, faster circadian adjustment to the shift-work schedule and promoting more sleep off-shift, compared to standard lighting. Methods A randomised controlled, within-subjects, counter-balanced cross-over study was performed to examine circadian-informed versus standard lighting on cognitive performance during a simulated 8-day night shift-work schedule. Nineteen healthy sleepers (12 males/7 females, mean±SD aged 28.7±10.4 years) underwent two separate 8-day experimental conditions in the sleep laboratory. The standard lighting condition mimicked current lighting on submarines (largely dim, blue-depleted light), while the circadian-informed lighting administered bright, blue-enriched and dim, blue-depleted lighting at times estimated to facilitate rapid circadian delay. After an adaptation sleep opportunity from 22:00 – 07:00 (day 1), participants remained awake for 27 hours to transition to sleeping during the day (10:00 - 19:00) and undertaking simulated night shift-work (00:00 - 08:00) at night on days 3-7. The primary performance outcome was the number of lapses (&amp;gt;500ms responses) on the psychomotor vigilance task (PVT), administered six times across each simulated work shift. Median reaction time and other PVT outcomes were also compared between lighting conditions. Results There were significant day-by-condition interactions on PVT lapses, p&amp;lt; 0.05. The circadian-informed lighting intervention resulted in ~50% fewer lapses by the final day compared to standard lighting (mean±SD 7.4±5.0 vs. 15.6±6.1 lapses). Similar effects were observed across other PVT outcomes. Conclusion Circadian-informed lighting resulted in markedly better vigilance than standard lighting under simulated night shift-work conditions. These findings indicate the considerable potential for automated lighting interventions to improve performance and safety in shift-workers. Support (if any) This research is supported by the Commonwealth of Australia as represented by the Defence Science and Technology Group of the Department of Defence through the Research Network for Undersea Decision Superiority (research agreement number: 9334), with additional financial support from Flinders University and lighting provision support from REDARC.

0282 Behavioral–social rhythms and metabolic syndrome prevalence in retired night shift and day workers

Abstract Introduction Disrupted sleep and circadian rhythms, such as those occurring during night shift work, are established cardiovascular disease (CVD) risk factors like hypertension, obesity, and insulin resistance. However, we do not know whether the effects of shift work on CVD risk factors persist into retirement. Conversely, regularity in behavioral-social rhythms – the systematic patterning or timing of daily routines like work/housework, sleeping, eating and social interactions – may keep endogenous circadian rhythms synchronized to the 24-hour day and reduce CVD risk. This study examined: 1) whether behavioral–social rhythms are associated with a major CVD risk factor, prevalent metabolic syndrome, in retired night shift workers and day workers; and 2) whether past night shift work exposure moderates the associations between behavioral–social rhythm and metabolic syndrome prevalence. Methods Participants were 71 retired night shift workers (39 women (54.9%), 32 men (45.1%)) and 83 retired day workers (46 women (55.4%), 37 men (44.6%)), with mean age 68.4 (5.4) years. Logistic regression models were used to examine associations between behavioral–social rhythms and metabolic syndrome prevalence. Independent variables included Social Rhythm Metric-5 (SRM5; a 5-item scale to quantify rhythms of daily life) score and actigraphy rest-activity rhythm inter-daily stability (IS; rhythm stability across days) and intra-daily variability (IV; rhythm fragmentation within days). The dependent variable was metabolic syndrome prevalence. Results More regular behavioral-social rhythms were associated with lower odds of having metabolic syndrome (SRM5: OR=0.57, 95%CI [0.35, 0.88]; IV (Higher score means lower regularity): OR=2.05, 95%CI [1.23, 3.44]). In addition, more regular behavioral-social rhythms were associated with lower odds of having two individual components of metabolic syndrome , body mass index (SRM5: OR=0.56, 95%CI [0.37, 0.85]; IV: OR=2.05, 95%CI [1.30, 3.23]) and high-density lipoprotein cholesterol level (SRM5: OR=0.49, 95%CI [0.30, 0.80]; IV: OR=1.78, 95%CI [1.06, 2.98]). Shift work exposure did not moderate the association between behavioral–social rhythms and metabolic syndrome prevalence. Conclusion Behavioral–social rhythms are related to metabolic syndrome prevalence in retired adults regardless of prior shift work exposure. Older retired workers may benefit from interventions that promote behavioral–social rhythm regularity. Support (if any) This research was supported by the NIH grants AG047139, HL082610, MH019986, and AG07517

0291 Attending Physician Perceptions of Nightshift Work in the ICU: Results from a Large Tertiary Medical Center

Abstract Introduction Nightshifts represent a substantial proportion of time dedicated to working in the inpatient setting, particularly among ICU staff. Our institution implemented a 24/7 in-person ICU attending model more than a decade ago. With practice growth and more than 200 ICU beds across disciplines, there are now at least 8 ICU attendings in-hospital all night. Yet, little is known about attending staff perceptions and desires about night work, so we began an exploratory analysis. Methods An online survey of 13 multiple-choice, slider scale, and open-ended questions were sent via email to critical care staff physicians of different disciplines within our institution. Results 69 out of 150 physicians completed the survey (46% response rate). Half were between 35 and 45 years old; 29% were age 45 to 55 years old. About half self-identified as a morningness chronotype. Most (84%) work 3- or 4-night shifts consecutively. Most viewed night shift work as having a negative influence on their quality of life (48% “somewhat negative” and 22% “very negative”) and on their health (51% “somewhat negative” and 24% “very negative”). Most would choose to work less nightshifts (37%) or none (29%). During nightshift assignments, about half (53%) self-report an average of 5 hours of sleep per 24-hour period; 18% self-report ≤ 4hours. Only 6% reported 7 or 8 hours of sleep. Mitigating strategies utilized during series of night shifts include use of caffeine (78%), naps (66%) and use of sleeping aids (21%). Outside of the nightshift series, more than half (56%) reported no sleep difficulties while 21% reported onset or maintenance insomnia. Conclusion At our large tertiary hospital employing an in-house nightshift model across multiple ICUs, most staff ICU physicians have a negative perception of night shift work on their quality of life and health. The majority of respondents would choose to work less or no night shifts. How self-reports of limited sleep (average 5 hours) per 24-hour period compare to objectively measured sleep duration in this population remains to be determined in the next phase of this study. Support (if any)

0246 Current shift work and frailty: findings from the UK Biobank

Abstract Introduction Shift work may disrupt sleep and circadian rhythms, leading to adverse health outcomes. The objective of this study is to examine whether performing shift work is associated with frailty in middle- to older-aged adults. Methods We examined current shift work exposure and frailty risk in 242,126 UK Biobank participants (38-71 years old; 128,595 females). Using the baseline self-reported employment information, participants were categorized as shift workers (with ‘work schedule that falls outside of the normal daytime working hours of 9am-5pm’) or day workers if no shift work schedule. Based on a previously validated approach, frailty phenotype was identified when three or more of the following five criteria were fulfilled: self-reported weight loss, exhaustion, low physical activity, slow walking pace, and measured low grip strength. Multivariate logistic regression models were used to assess the association between shift work and frailty. Results Among 242,126 participants, 201,489 (83.2%) were day workers and 40,637 (16.8%) shift workers. Frailty was identified in 4,308 participants (1.8%), including 3,312 day workers (1.6%) and 996 shift workers (2.5%). Compared with day workers, shift workers were at higher risk for frailty after adjusting age, sex, and ethnicity, i.e., odds ratio (OR) =1.58 [95% CI, 1.47-1.70] (p &amp;lt; 0.0001). The effect of shift work appeared to be more pronounced in 5,659 permanent night shift workers (OR = 1.98 [95% CI, 1.68-2.32], p &amp;lt; 0.0001). The differences between day workers and shift workers persisted even after further adjusting for social economic status, sleep duration, and chronotype (OR = 1.38 [95% CI, 1.28-1.48] for all shift workers; OR = 1.53 [95% CI, 1.30-1.80] for permanent night shift workers, both p values &amp;lt; 0.0001). Conclusion Middle- to older-aged adults who were currently performing shift work, especially those permanent night shift workers, were more likely to be frail. Longitudinal and interventional studies are warranted to elucidate the causal relationship between shift work and the risk of frailty. Support (if any) BrightFocus Foundation (A2020886S), NIH (RF1AG059867, RF1AG064312)

0297 Pathways: A Pilot Study Examining the Impact of Nightshift Work on Obesity and Type 2 Diabetes Risk in Free-Living Shift Workers

Abstract Introduction Traditional risk factors for obesity and type 2 diabetes, such as poor diet and low physical activity, cannot fully explain the increased incidence of these diseases. Insufficient sleep and circadian misalignment due to shift work may contribute, in part, to this epidemic through their growing prevalence and associated impaired glucose regulation and eating out of phase. Methods Female nightshift healthcare workers (n=5) worked ≥2 shifts (~7pm-7am) during the 7-day study. Actigraphy was measured and participants wore continuous glucose monitors and completed three 24-hour dietary recalls. Dim light melatonin onset was predicted (pDLMO) for each worker from an actigraphy derived algorithm validated for shift workers. The timepoints two hours after (pDLMO+2) and 10 hours after (pDLMO+10) predicted DLMO are presented as a range in which sleep typically occurs, on average, relative to DLMO. Results Mean participant age was 30.7 years and body mass index 22.8 kg/m2. Dietary recalls report the average total energy consumed on workdays to be 1,653 kcal ± 444 (mean ± SD) compared to 1,517 kcal ± 421 on free days (p=0.64). Average eating windows were 13.88 ± 2.69 hours on nightshifts compared to 9.88 ± 1.82 hours on workfree days (p=0.051, n=4 one individual did not report eating while on shift). Further, eating occasions between 10pm–7:30am were only reported on worknights. Average pDLMO was 23.26 ± 1.27 hours, corresponding to the middle of shift. The average interstitial glucose level between pDLMO+2 and pDLMO+10 on shift was 88.4 mg/dL ± 9.0 and the average during the same interval on workfree nights was 81.1 mg/dL ± 7.0 (p = 0.024). Additionally, an increase in 24-hour average glucose was observed on shift 90.9 ± 4.9 compared to free days 86.1 ± 6.2 (p=0.021). Conclusion Early results from this ongoing study show that an extended eating window, eating overnight, and/or working overnight contribute to increased glucose levels while night workers are on shift compared to their days off. Increased overnight glucose levels, especially at a time the body may be accustomed to sleeping, represent a time of impaired glucose tolerance and potentially reduced insulin sensitivity. Support (if any) Anschutz CCTSI Pilot Grant Award, CTSA Grant UL1 TR002535

Preliminary Study on the Effect of a Night Shift on Blood Pressure and Clock Gene Expression.

Night shift work has been found to be associated with a higher risk of cardiovascular and cerebrovascular disease. One of the underlying mechanisms seems to be that shift work promotes hypertension, but results have been variable. This cross-sectional study was carried out in a group of internists with the aim of performing a paired analysis of 24 h blood pressure in the same physicians working a day shift and then a night shift, and a paired analysis of clock gene expression after a night of rest and a night of work. Each participant wore an ambulatory blood pressure monitor (ABPM) twice. The first time was for a 24 h period that included a 12 h day shift (08.00-20.00) and a night of rest. The second time was for a 30 h period that included a day of rest, a night shift (20.00-08.00), and a subsequent period of rest (08.00-14.00). Subjects underwent fasting blood sampling twice: after the night of rest and after the night shift. Night shift work significantly increased night systolic blood pressure (SBP), night diastolic blood pressure (DBP), and heart rate (HR) and decreased their respective nocturnal decline. Clock gene expression increased after the night shift. There was a direct association between night blood pressure and clock gene expression. Night shifts lead to an increase in blood pressure, non-dipping status, and circadian rhythm misalignment. Blood pressure is associated with clock genes and circadian rhythm misalignement.

Melatonin: A Potential Regulator of DNA Methylation.

The pineal gland-derived indoleamine hormone, melatonin, regulates multiple cellular processes, ranging from chronobiology, proliferation, apoptosis, and oxidative damage to pigmentation, immune regulation, and mitochondrial metabolism. While melatonin is best known as a master regulator of the circadian rhythm, previous studies also have revealed connections between circadian cycle disruption and genomic instability, including epigenetic changes in the pattern of DNA methylation. For example, melatonin secretion is associated with differential circadian gene methylation in night shift workers and the regulation of genomic methylation during embryonic development, and there is accumulating evidence that melatonin can modify DNA methylation. Since the latter one impacts cancer initiation, and also, non-malignant diseases development, and that targeting DNA methylation has become a novel intervention target in clinical therapy, this review discusses the potential role of melatonin as an under-investigated candidate epigenetic regulator, namely by modulating DNA methylation via changes in mRNA and the protein expression of DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) proteins. Furthermore, since melatonin may impact changes in the DNA methylation pattern, the authors of the review suggest its possible use in combination therapy with epigenetic drugs as a new anticancer strategy.

Association of intra-shift nap duration with heart rate variability in medical night shift workers.

Napping during night shifts effectively reduces disease risk and improves work performance, but few studies have investigated the association between napping and physiological changes, particularly in off-duty daily lives. Changes in the autonomic nervous system precede diseases like cardiovascular disease, diabetes, and obesity. Heart rate variability is a good indicator of autonomic nervous system. This study aimed to investigate the link between night shift nap durations and heart rate variability indices in the daily lives of medical workers. As indicators of chronic and long-term alterations, the circadian patterns of heart rate variability indices were evaluated. We recruited 146 medical workers with regular night shifts and divided them into four groups based on their self-reported nap durations. Heart rate variability circadian parameters (midline-estimating statistic of rhythm, amplitude, and acrophase) were obtained by obtaining 24-h electrocardiogram on a day without night shifts, plotting the data of the heart rate variability indices as a function of time, and fitting them into periodic cosine curves. Using clinical scales, depression, anxiety, stress, fatigue, and sleepiness were assessed. Linear regression analysis revealed a positive relationship between 61-120-min naps and 24-h, daytime, and night-time heart rate variability indices, and the parasympathetic activity oscillation amplitude (indexed by high-frequency power, the square root of the mean of the sum of squares of differences between adjacent normal intervals, standard deviation of short-term R-R-interval variability) within one circadian cycle. This study indicated that napping for 61-120 min during night shifts could benefit medical workers' health, providing physiological evidence to promote nap management.