Early Morning Shifts Research Articles

Expert-based assessment of chemical and physical exposures, and organizational factors, in past agricultural jobs

BackgroundLimited data document the spectrum of exposures in the agricultural environment. We describe here the wide range of chemical and physical agents, and organizational factors, encountered in agricultural jobs held in the past in Canada and abroad. MethodsWe used data from a population-based case-control study of prostate cancer including 3,925 male participants residing in Montreal, Canada in 2005-2012. Lifetime occupational histories and detailed job descriptions were collected in-person. Industrial hygienists and an agronomist conducted semi-quantitative evaluations of exposure, including intensity and reliability, to some 300 chemical and physical agents in each job held. Analyses focused on the 156 agricultural jobs ever held in the study population. Clusters of agricultural co-exposures were derived. ResultsAgricultural jobs had taken place in 1946-2012, 53% ending in 1970 or after. Jobs were often (43%) held in Quebec, Canada; 22% in Italy, Portugal or Greece, and 10% in Haiti. Jobs entailed exposure to an average of 10 chemical agents (± 7) and most were characterized by long working hours, high physical activity levels, and did not provoke stress or anxiety. Few involved early morning shifts. Exposure to 78 agents was assigned with probable or definite certainty. The most common definite or probable carcinogens were ultraviolet radiation (92% of jobs), environmental tobacco smoke (39%), diesel engine exhaust (23%), wood dust (20%), lubricating oils and greases (20%) and lead (15%). Pesticide exposure (as a group) occurred in 31% of jobs. Fifty-four percent of jobs entailed exposure to ≥ 2 recognized carcinogens. Exposure clusters varied according to countries and type of agricultural activities (general, animal, crops, horticulture, vineyards, etc.). ConclusionsFindings highlight the heterogeneity of exposure patterns in past agricultural environments based on their setting and activities involved. Studies on health-related effects of farming should account for numerous potential exposures, beyond their typical focus on pesticides.

Night work, circadian rhythm, and cognitive performance: A field study with airport security screeners

The effects of circadian rhythms and night work on performance have been extensively studied using standardized, non-work-related tasks in laboratory settings. However, field research on work performance is scarce in this domain. This study addresses this gap by analyzing four million behavioral responses from 1437 security officers at an international airport. We compared threat detection performance during the routine security screening of passengers' baggage X-ray images across night shifts (shift starting between 0:00 and 2:59), early morning shifts (starting between 3:00 and 5:59), and standard morning shifts (starting between 6:00 and 7:59). Processing times followed the circadian rhythm of attention found in laboratory studies, indicating that the rhythm affects real-life work performance. False alarm rates (i.e. false target present responses) were slightly higher during night and early morning shifts than during standard morning shifts, with no significant difference in the security-relevant hit rates (i.e. true target present responses). Furthermore, we found no performance differences between night work and early morning shifts, suggesting that both can disrupt employees’ natural sleep patterns with implications on performance.

0614 Characterizing Sleep in Early-Morning Shift Workers at Risk for Shift Work Disorder

Abstract Introduction Shift work is increasingly common in our 24/7 society and can cause sleep disturbances and excessive sleepiness. Roughly 10-43% of shift workers are diagnosed with shift work disorder (SWD), characterized by excessive sleepiness accompanied by reduced sleep duration and/or insomnia. While more individuals work early morning shifts (shift start 3-6AM) compared to overnight shifts, few studies have investigated this population. The aim of this study was to characterize sleep in a population of early-morning shift workers. Methods We characterized sleep in early-morning shift workers (18-65yrs) from New England who were screened for a clinical trial of a wake-promoting agent. Pre-screening consisted of the Epworth Sleepiness Scale (ESS) and a Shift Work Disorder Questionnaire (SWD); screening consisted of the Pittsburg Sleep Quality Index Questionnaire Questionnaire (PSQI) ; a physical exam including an ECG, CBC, urinalysis, and comprehensive metabolic panel; a home sleep test (HST), a Monitored Wakefulness Test (MWT); a physician evaluation of their excessive sleepiness (Clinical Global Impression [CGI]); and a self-evaluation regarding how sleepiness affected their everyday life (Patient Global Impression [PGI]). Only data from consented individuals who met the initial inclusion criteria of being high risk for SWD were included in the analysis. Results 158 early-morning shift workers met the pre-screening criteria and began the screening process. Most worked in retail, healthcare, maintenance, or transportation, and worked five shifts (65%) and 40+ hours (72%) per week, with a duration of 8.8±1.9 hours. 41 were screened out for abnormal findings on the PE, ECG, or screening blood/urine tests; 26 were screened out for previously un-diagnosed OSA or PLMD; 4 were ineligible for other reasons; 7 were excluded after their MWT due to long sleep latency, 20 were lost to follow-up/withdrew and 60 completed screening and met inclusion criteria. Their average (±sd) age was 37±11 years, 45% women, PSQI score 7.5±2.7, sleep duration 5.6±1.0, ESS=16.3±3.1, CGI=4.2±0.9, PGI=3.6±1.1. Conclusion Early-morning shift workers at an increased risk for SWD report short and disturbed sleep, excessive sleepiness, and a negative impact of sleepiness on their quality of life. Many have undiagnosed OSA and PLMD. Support (if any) Axsome Therapeutics, Jazz Pharmaceuticals, Brigham and Women’s Hospital Center for Clinical Investigation.

Brighter Than the Sun by Daniel Aleman (review)

Reviewed by: Brighter Than the Sun by Daniel Aleman Amanda Toledo Aleman, Daniel Brighter Than the Sun. Little, 2023 [352p] Trade ed. ISBN 9780316704472 $18.99 E-book ed. ISBN 9780316704519 $10.99 Reviewed from digital galleys Ad Gr. 9-12 The only member of her family born in the United States, sixteen-year-old Sol (short for María de la Soledad) crosses from Tijuana to San Diego each morning to attend high school. The early mornings are exhausting, not to mention Sol's worries about getting food on the table for her family and her ever present grief over her mother's death a year ago. Sol ends up moving in with her best friend Ari in San Diego to be able to work early morning and late-night shifts at a department store, and she's hoping what she earns will not only help her Papi pay the bills but [End Page 247] also save their family restaurant. Unfortunately, but understandably, Sol begins to buckle beneath the pressure of trying to balance work, school, and her family, especially as her feelings of loneliness and isolation grow. Aleman's direct, accessible prose believably conveys the heavy responsibility teens carry as they support their struggling families, but the lack of description of the setting and emotional details makes some scenes fall flat. The recurring theme of loneliness is an important one, but the exploration is heavy handed with too many occurrences of Sol contemplating her dual-self represented by her name Sol-the sun, and "Soledad-Solitude." Still, the emotional stakes here are compelling, and amidst all the hardship, Aleman inserts potent moments of joy and connection, the power of female friendship, and the perseverance of possibility. Copyright © 2023 The Board of Trustees of the University of Illinois

Variation on Work Demands and Sleep Disturbances Concerning Fixed and Rotating Shifts in the Water, Sanitation, and Waste Sector

The growing production of waste and increased use of water and sanitation systems worldwide have been pressuring the water, sanitation, and waste sectors. This study analyzed the perception of the determinants of work activity among workers from the water, sanitation, and waste sector in Portugal, the variation in the work demands among different shift types, and the main predictors of sleep disturbances. Data collection was performed through a questionnaire administered to 300 workers in 2017 and 2019. An ageing population was identified in all shift types. Possible occupational trajectories with changes from the fixed night and early morning shifts to daytime and fast rotating shifts may be linked to health conditions. Workers in fixed night and early morning shifts perceived higher physical demands and environmental discomfort, lower social support, and job dissatisfaction. Workers in daytime or fast rotating shifts perceived higher cognitive demands. Sleep disturbances were perceived more negatively among those working permanently on night and early morning shifts. The main predictors of sleep disturbance in both years were the type of shift, and high physical demands. The study highlights the relevance of characterizing the work demands to establish future strategies to improve the health and well-being of shift workers.

The association of schedule characteristics of heavy vehicle drivers with continuous eye-blink parameters of drowsiness

Study objectivesWhile drowsiness contributes to 20% of heavy vehicle crashes, the impact of work schedules on heavy vehicle driver (HVD) drowsiness is unclear. This study explored the impact of work schedules on drowsiness (measured by infrared oculography) in HVDs. MethodWork and drowsiness monitoring (Optalert, Australia) of ten HVDs, aged 37–62 years collected nearly 2430 h of work and 1068 h of oculography data during four weeks of naturalistic drives. Drowsiness events were defined as a John's Drowsiness Scores ≥ 2.6. Nine HVDs slept for 5.82 ± 1.37 h during five weeks of actigraphy. Association of driving schedule characteristics and drivers’ continuous eye-blink parameters were observed using logistic and mixed linear regression analyses. ResultsCombination of time of day (10 pm- 2 am), shift start time (2 pm-3 pm), hours into the shift (16–21 h), break duration (7–9 h), and sleep time (<6 h) increased the likelihood of drowsiness events when controlling for other covariates. A combination of night times (6 pm to 2 am), 18 to 21 h into the shift, shift start times (6 am to 7 am), shifts lengths (8 to15 h) and break times (<7 to 9 h) increased the hourly rate of drowsiness significantly when adjusting for other covariates. ConclusionsThe combination of prolonged work hours, night-time drives, early-morning shift starts and short breaks increase drowsiness rates in HVDs. Large datasets are needed to examine the interplay between sleep time, consecutive shifts and shift order and type with this combination.

Shift work and insulin resistance (HOMA-IR) among professional drivers.

Shift work may be associated with insulin resistance. This study aimed to investigate the potential association between shift work and the homeostatic model assessment of insulin resistance (HOMA-IR) index in professional drivers. A total of four hundred fifty-three professional drivers were invited to participate in the study within a periodic medical examination in the occupational setting. One hundred seventy-seven daytime workers were compared with 175 night shifts and 101 early morning shift drivers. Demographic, occupational, and medical examination including blood pressure, anthropometric data was assessed. Measurement of serum insulin, fasting blood glucose and lipid profile were done for all drivers. Compared with day workers, night shift and early morning shift drivers displayed higher levels of HOMA-IR. Metabolic syndrome was found to be significantly increased in night workers. In linear regression analysis, insulin resistance was correlated with shift work independently of demographic and occupational characteristics. The study revealed that shift work could be a risk factor in developing the risk of metabolic syndrome and insulin resistance. Suggestively, health strategies such as structured lifestyle counseling in occupational health settings are warranted to improve and modify cardiometabolic risk factors.

Changes in melatonin and sex steroid hormone production among men as a result of rotating night shift work - the HORMONIT study.

ObjectiveData from real world settings on circadian disruption and subsequent hormone-related changes may explain the higher risk of hormone-dependent cancers among night shift workers.The present study examines the melatonin and sex steroid hormone levels among night shift workers.MethodsWe included 44 male, rotating shift workers from a car factory in Spain, sampled both at the end of a 3-week night shift (22:00–06:00 hrs) and a 3-week early morning shift (06:00–14:00 hrs). Participants collected all urine voids over 24-hours during each shift. Urinary concentrations of sex steroid hormones (estrogens, androgens and progestogens) and 6-sulfatoxymelatonin (aMT6s, major melatonin metabolite) were determined. Individual cosinor analysis was used to derive the acrophase (peak time) and area under the curve (total production). Linear mixed models examined intraindividual associations between night shift work and log-transformed 24-hour peak time and total production of hormones compared to early morning shift work.ResultsThe acrophase was delayed during the night shift for aMT6s [geometric mean difference (GMD) 7.53 hrs, 95% confidence interval (CI) 4.46–10.60], androgens (eg, testosterone: GMD 6.83 hrs, 95% CI 0.34–13.32) and progestogens (eg, 17-hydroxyprogesterone: GMD 4.54 hrs, 95% CI 2.92–6.16) compared to the early morning shift. We found a higher production of adrenal androgen 11-oxoandrosterone/11-oxoetiocholanolone [geometric mean ratio (GMR) 1.43, 95% CI 1.12–1.81], and a lower production of adrenal progestogen 16-cysteinylprogesterone (GMR 0.79, 95% CI 0.67–0.93) during the night shift compared to the early morning shift levels.ConclusionsNight shift work was associated with melatonin and sex hormone-related changes in timing and total production, providing insight into the mechanistic path for its association with hormone-dependent cancer.

Night-Shift Work and Risk of Prostate Cancer: Results From a Canadian Case-Control Study, the Prostate Cancer and Environment Study

Night-shift work involving disruption of circadian rhythms has been associated with breast cancer risk. A role in prostate cancer is also suspected, but evidence is limited. We investigated the association between night-shift work and prostate cancer incidence in the Prostate Cancer and Environment Study (PROtEuS), a population-based case-control study conducted in 2005-2012 in Montreal, Quebec, Canada. Participants were 1,904 prostate cancer cases (432 high-grade cancers) and 1,965 population controls. Detailed work schedules for each job held for at least 2 years (n = 15,724) were elicited in face-to-face interviews. Night-shift work was defined as having ever worked ≥3 hours between midnight and 5:00 am ≥3 nights/month for ≥1 year. Unconditional logistic regression was used to estimate odds ratios and 95% confidence intervals for the association between night-shift work and prostate cancer, adjusting for age, ancestry, and education. No association was found between overall prostate cancer and night-shift work metrics, including ever exposure, duration, intensity, cumulative exposure, rotating shifts, and early-morning shifts. For none of the exposure indices was there evidence of heterogeneity in odds ratios between low- and high-grade cancers. Sensitivity analyses restricting exposures to ≥7 nights/month or considering screening history yielded similar results. Our findings lend no support for a major role of night-shift work in prostate cancer development.

Working hour characteristics and schedules among nurses in three Nordic countries \u2013 a comparative study using payroll data

BackgroundOrganisation of working hour schedules in the Northern European countries are rather similar. EU countries are obliged to adopt national legislation regarding duration of weekly working hours and rest periods. Yet, working hour characteristics and schedules are likely to differ with respect to starting times and duration depending e.g. on culture and tradition. Yet, very little is known about potential differences between shifts and schedules across countries among nursing personel. This knowledge is relevant, since the potential differences in working hour characteristics may influence and possibly explain some of the differences observed in studies of health and safety.The aim of the study was to compare characteristics of working hours and work schedules among nursing personel in three Nordic countries: Denmark, Finland and Norway.MethodsThe study populations included nursing personnel holding a ≥ 50% position at public hospitals in Denmark (n = 63,678), Finland (n = 18,257) or Norway (n = 1538) in 2013. Objective payroll based registry data with information on daily starting and ending times were used to compare working hour characteristics e.g. starting time, duration of shift, and quick returns (< 11 h between two shifts), as well as work schedules e.g. permanent or 3-shift work between the three countries.ResultsNight shifts generally started earlier and lasted longer in Finland (10–11 h starting at 20:00–22:59) than in Norway (10 h starting at 21:00–21:59) and in Denmark (8 h starting at 23:00–23:59). Very long shifts (≥12 h) were more common in Denmark (12%) compared to Finland (8%) and Norway (3%). More employees had many (> 13/year) quick returns in Norway (64%) and Finland (47%) compared to Denmark (16%). The frequency of 3-shift rotation workers was highest in Norway (41%) and lower in Denmark (22%) and Finland (22%). There were few differences across the countries in terms of early morning shifts and (very) long weekly working hours.ConclusionDespite similar distribution of operational hours among nurses in the three countries, there were differences in working hour characteristics and the use of different types of work schedules. The observed differences may affect health and safety.

Behavior of buffalo heifers reared in shaded and unshaded pastures during the dry season on Marajó Island, Pará, Brazil

The objective of this research was to evaluate the behavior of twenty buffalo heifers reared during the dry season on Marajó Island, Pará, Brazil. The animals were distributed into two groups, those with shade (WS) and those without shade (WOS). The experimental day was divided into six shifts: morning (6:00 to 9:55 a.m.), intermediate (10:00 a.m. to 1:55 p.m.), afternoon (2:00 to 5:55 p.m.), evening (6:00 to 9:55 p.m.), night (10:00 p.m. to 1:55 a.m.), and early morning (2:00 to 5:55 a.m.). The WS group was kept in silvipastoral system paddocks, while the WOS group was kept in unshaded paddocks. Climatic data were registered and temperature and humidity index (THI) were calculated. Behavior data such as grazing, rumination, idle time, and other activities (walking, defecating, mounting, drinking water, urinating, eating salt) were evaluated. The results showed that the THI was higher in the WOS group. Grazing time was higher in the WOS group than in the WS group in the intermediate shift (p &lt; 0.05), while in the afternoon, evening, and early morning shifts, the WS group spent more time grazing than the WOS group. In the intermediate and early morning shifts, the WS group spent more time ruminating (p &lt; 0.05); the WS group ruminated more than the WOS group. The WOS group had more idle time, especially in the evening and early morning shifts (p &lt; 0.05), while the WS group had more idle time in the intermediate shift (p &lt; 0.05). We conclude that buffaloes graze and ruminate more intensely when they are reared in a shaded system on the island of Marajó.

Assessment of work-related stress by using salivary cortisol level examination among early morning shift workers.

Early morning shifts have a negative effect on the hypothalamic-pituitary-adrenal axis. The aim of this study was to comprehensively assess the extent of occupational stress in early shift workers of the car industry by using salivary cortisol as an objective marker during a workday and on a day off. For this cross-sectional epidemiological type of study, a survey included 55 suitable volunteers from the car industry. Five saliva samples were collected according to the following schedule: during one work day in the morning, during the morning shift from 6 a.m. - 2 p.m., then after the shift was completed, 3 hours after work and in the evening before going to sleep. Control samples were taken from the same participants on a day off. Radioimmunoanalysis was used as the main analytical method, and the effect of factors and between-factor interactions on the levels of salivary cortisol during the workday were assessed using an ANOVA model. The cortisol diurnal rhythm was as expected, with the highest values in the morning and declining to the lowest values in the evening hours. Concentrations of salivary cortisol showed higher values during the workday, especially higher concentrations of evening cortisol and attenuated cortisol slope. Based on the results, irregular shift work has a greater increase in cortisol excretion after waking in the morning and a slower progressive recovery of the organism during the workday. In addition, cortisol levels were significantly higher in older women than in older men but did not differ in younger subjects. Salivary cortisol levels are a suitable objective marker of stress and can be used as a good predictor of occupational stress by public health services for the purposes of primary prevention.

Effects of alertness management training on sleepiness among long-haul truck drivers: A randomized controlled trial

Education is a frequently recommended remedy for driver sleepiness in occupational settings, although not many studies have examined its usefulness. To date, there are no previous on-road randomized controlled trials investigating the benefits of training on sleepiness among employees working in road transport. To examine the effects of an educational intervention on long-haul truck drivers’ sleepiness at the wheel, amount of sleep between work shifts, and use of efficient sleepiness countermeasures (SCM) in association with night and non-night shift, a total of 53 truck drivers operating from southern Finland were allocated into an intervention and a control group using a stratified randomization method (allocation ratio for intervention and control groups 32:21, respectively). The intervention group received a 3.5-hour alertness management training followed by a two-month consultation period and motivational self-evaluation tasks two and 4–5 months after the training, while the control group had an opportunity to utilize their usual statutory occupational health care services. The outcomes were measured under drivers’ natural working and shift conditions over a period of two weeks before and after the intervention using unobtrusive data-collection methods including the Karolinska Sleepiness Scale measuring on-duty sleepiness, a combination of actigraphy and a sleep-log measuring sleep between duty hours, and self-report questionnaire items measuring the use of SCMs while on duty. The data analysis followed a per-protocol analysis. Results of the multilevel regression models showed no significant intervention-related improvements in driver sleepiness, prior sleep, or use of SCMs while working on night and early morning shifts compared to day and/or evening shifts. The current study failed to provide support for a feasible non-recurrent alertness-management training being effective remedy for driver sleepiness in occupational settings. These results cannot, however, be interpreted as evidence against alertness management training in general but propose that driver education is not a sufficient measure as such to alleviate driver sleepiness.

A Preliminary Review of Fatigue Among Rail Staff.

Background: Fatigue is a severe problem in the rail industry, which may jeopardize train crew's health and safety. Nonetheless, a preliminary review of all empirical evidence for train crew fatigue is still lacking. The aim of the present paper is, therefore, to provide a preliminary description of occupational fatigue in the rail industry. This paper reviews the literature with the research question examining the risk factors associated with train crew fatigue, covering both papers published in refereed journals and reports from trade organizations and regulators. It assesses the progress of research on railway fatigue, including research on the main risk factors for railway fatigue, the association between fatigue and railway incidents, and how to better manage fatigue in the railway industry.Methods: Systematic searches were performed in both science and industry databases. The searches considered studies published before August 2017. The main exclusion criterion was fatigue not being directly measured through subjective or objective methods.Results: A total of 31 studies were included in the main review. The causes of fatigue included long working hours, heavy workload, early morning or night shifts, and insufficient sleep. Poor working environment, particular job roles, and individual differences also contributed to fatigue.Conclusion: Fatigue in the rail industry includes most of the features of occupational fatigue, and it is also subject to industry-specific factors. The effect of fatigue on well-being and the fatigued population in the railway industry are still not clear. Future studies can consider associations between occupational risk factors and perceived fatigue by examining the prevalence of fatigue and identifying the potential risk factors in staff within the railway industry.

Common Sleep, Psychiatric, and Somatic Problems According to Work Schedule: an Internet Survey in an Eastern European Country.

A wide range of health problems was investigated, aiming to identify the presence and severity of a set of self-reported and common sleep, psychiatric, and somatic health problems among working professionals in four different shift schedules (morning, evening, rotating, and day) in several cities in Romania. A heterogeneous sample of 488 workers of different professions completed online a battery of tests, namely the Basic Nordic Sleep Questionnaire, the Parasomnia Questionnaire, the Epworth Sleepiness Scale, and the Patient Health Questionnaire, designed to identity symptoms of insomnia, sleepiness, snoring, parasomnia, as well as of depression, anxiety, eating, somatoform, and alcohol use disorders, respectively. The timing and the duration of the sleep, along with the presence of high blood pressure and type 2 diabetes mellitus were also inquired. The prevalence of the different health problems in relation to the type of shift schedule was evaluated with the Pearson Chi-square test. ANOVA was used to calculate the significance of the difference between the means, while associations with different health problems were estimated by binary logistic regression. The most common mental health problems were depression (26%), insomnia (20%), alcohol misuse (18%), and anxiety (17%). No significant differences based on the type of shift in terms of health problems were found, except for high blood pressure and symptoms of panic disorder that were more frequently reported by the workers in early morning shifts. Together with the workers in rotating shifts, they also reported increased sleepiness, poorer sleep quality, and shorter sleep duration. In contrast, the workers in evening shifts reported less severe health problems and longer sleep duration. Working in early morning shifts was found to be associated with poorer health outcomes, while working in rotating and early morning shifts with more severe sleep-related problems.

Application effects of regulating the morning shift on high-quality nursing care

Objective To investigate the application effects of regulating the daily morning shift on high-quality nursing care. Methods A total of 497nurses and 777 patients from Beijing Friendship Hospital of Capital Medical University were investegated during early morning shift from January 2014 to August 2015. The nursing department assembled a panel to implement the morning shift procedure. The hospital training institute group was responsible for the nurses training and the supervision in clinical practice. Results After the shift regulation, nurses were able to quickly concentrate on the priorities, and patients could better understand their conditions (P<0.05). The satisfactions for both nurses and patients were highly improved and the shifting time was significantly reduced (P<0.05) . Conclusions The optimized morning shift procedure not only can promote the quality and efficiency of shifting but also can improve the satisfaction and patients' awareness of their health status. Key words: Morning shift; Procedure optimization; High quality nursing care

Cesarean section and the manipulation of exact delivery time

Physicians are often alleged responsible for the manipulation of delivery timing. We investigate this issue in a setting that negates the influence of financial incentives on physician's behavior. Working on a sample of women admitted at the onset of labor in a big public hospital in Italy we estimate a model for the exact time of delivery as driven by individual Indication to Cesarean Section (ICS) and covariates. We find that ICS does not affect the day of delivery but leads to a circadian rhythm in the likelihood of delivery. The pattern is consistent with the postponement of high ICS deliveries in the late night\\early morning shift. Our evidence hardly supports the manipulation of timing of births as driven by medical staff's “demand for leisure”. Physicians seem to manipulate the exact timing of delivery to reduce exposure to risk factors extant during off-peak periods.

Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: can we reduce morning bright-light duration?

ObjectiveEfficient treatments to phase-advance human circadian rhythms are needed to attenuate circadian misalignment and the associated negative health outcomes that accompany early-morning shift work, early school start times, jet lag, and delayed sleep phase disorder. This study compared three morning bright-light exposure patterns from a single light box (to mimic home treatment) in combination with afternoon melatonin. MethodsFifty adults (27 males) aged 25.9 ± 5.1 years participated. Sleep/dark was advanced 1 h/day for three treatment days. Participants took 0.5 mg of melatonin 5 h before the baseline bedtime on treatment day 1, and an hour earlier each treatment day. They were exposed to one of three bright-light (~5000 lux) patterns upon waking each morning: four 30-min exposures separated by 30 min of room light (2-h group), four 15-min exposures separated by 45 min of room light (1-h group), and one 30-min exposure (0.5-h group). Dim-light melatonin onsets (DLMOs) before and after treatment determined the phase advance. ResultsCompared to the 2-h group (phase shift = 2.4 ± 0.8 h), smaller phase-advance shifts were seen in the 1-h (1.7 ± 0.7 h) and 0.5-h (1.8 ± 0.8 h) groups. The 2-h pattern produced the largest phase advance; however, the single 30-min bright-light exposure was as effective as 1 h of bright light spread over 3.25 h, and it produced 75% of the phase shift observed with 2 h of bright light. ConclusionsA 30-min morning bright-light exposure with afternoon melatonin is an efficient treatment to phase-advance human circadian rhythms.

Assessment of exposure to shiftwork mechanisms in the general population: the development of a new job-exposure matrix

ObjectiveTo develop a job-exposure matrix (JEM) that estimates exposure to eight variables representing different aspects of shiftwork among female workers.MethodsOccupational history and shiftwork exposure data were obtained from a population-based...

Adipokine Levels Are Altered by Shiftwork: A Preliminary Study

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n = 9), working from 22:00 to 06:00 h; (ii) early morning shift (n = 6), working from 06:00 to 14:00 h; and (iii) day shift (n = 7), working from 08:00 to 17:00 h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24 h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p < .03). Both shiftworker groups ingested a significantly higher percentage of fat (p < .003) and a lower percentage of carbohydrate (p < .0005) than the day group. The early morning group had a lower mean 24-h level of adiponectin than the other two groups (p = .016), and both the early morning and night groups exhibited higher mean 24-h levels of TNF-α than the day group (p = .0001). The 24-h mean levels of IL-6 did not differ significantly between the groups (p = .147). None of the groups exhibited a significant circadian effect on adiponectin (p = .829), TNF-α (p = .779), or IL-6 (p = .979) levels. These results indicate that individuals who are enrolled in shiftwork are susceptible to alterations in the secretion of cytokines that are involved in insulin resistance and cardiovascular disease, both of which are known to affect this population. (Author correspondence: tmello@demello.net.br)