Hours of work and rest in the rail industry

Currently, the National Transport Commission is considering four options to form the regulatory framework for rail safety within Australia with respect to fatigue. While the National Transport Commission currently recommends no limitations around hours of work or rest, we provide evidence which suggests regulatory frameworks should incorporate a traditional hours of service regulation over more flexible policies. Our review highlights: Shift durations >12 h are associated with a doubling of risk for accident and injury. Fatigue builds cumulatively with each successive shift where rest in between is inadequate (<12 h). A regulatory framework for fatigue management within the rail industry should prescribe limits on hours of work and rest, including maximum shift duration and successive number of shifts. Appropriately, validated biomathematical models and technologies may be used as a part of a fatigue management system, to augment the protection afforded by limits on hours of work and rest. A comprehensive sleep disorder screening and management programme should form an essential component of any regulatory framework.

Job strain, sleep and alertness in shift working health care professionals -- a field study

We explored the associations of job strain with sleep and alertness of shift working female nurses and nursing assistants. Participants (n=95) were recruited from the Finnish Public Sector Study, from hospital wards that belonged to the top or bottom quartiles on job strain. Participants' own job strain was at least as high in high-strain group or low in low-strain group as the ward's average. The study included three-week measurements with sleep diary and actigraphy. Psychomotor Vigilance Test (PVT) was performed during one pre-selected morning and night shift and a day off. Sleep efficiency before morning shifts was lower in the high-strain than low-strain group (p=0.03). Low-strain group took more often (72 vs. 45%; p<0.01) and longer naps (62 vs. 35 min; p=0.01) before the first night shift than high-strain group. Difficulties initiating sleep were more common in high-strain group, especially after evening shifts (p<0.01). High-strain group had more often at least one lapse in PVT during the night shift (p=0.02). Average sleep duration (06:49 h) and efficiency (89%) did not differ between these groups. In conclusion, high job strain is associated with difficulties initiating sleep and reduced psychomotor vigilance in night shifts. Shift working contributed to impaired sleep in both high and low job strain group. Individual and organization-based actions are needed to promote sufficient sleep in shift working nurses, especially with high job strain.

Correlates of negative physical health in call center shift workers

The call center industry, a burgeoning sector is characterized by unique job demands, which render it susceptible to high attrition rates and negative health concerns. This study examined the relationship between job stress from interpersonal factors, job stress from work factors, coping, inadequate sleep, and negative physical health reports among call center shift workers (n = 239), a relatively under-researched population. Inadequate sleep and job stress from interpersonal factors were associated with negative physical health outcome for the participants in this study. Further, spending longer in the call center industry was associated with negative health outcome for the shift worker participants.

Sleep deprivation and its consequences on house officers and postgraduate trainees

OBJECTIVE

To determine sleep deprivation and its consequences on doctors in tertiary care hospitals.

METHODS

The cross-sectional study was conducted from February to May 2012 and comprised house officers and postgraduate trainees at 4 public and 1 private tertiary care hospitals in Karachi. The subjects were posted in wards, out-patient departments and emergencies. A proforma was designed with questions about duration of duty hours, sleep deprivation and its effects on quality of performance, and presence of anxiety, depression, medical errors, frequent cold and infections, accidents, weight changes, and insomnia. Duration of 1 hour was given to fill the proforma. SPSS 20 was used for data analysis.

RESULT

The study comprised 364 subjects: 187 (51.37%) house officers and 177 (48.62%) postgraduate trainees. There were 274 (75.27%) females and 90 (24.72%) males. Of those who admitted to being sleep deprived (287; 78.84%), also complained of generalised weakness and poor performance (n = 115; 40%), anxiety (n = 110; 38%), frequent cold and infections (n = 107; 37%), personality changes (n = 93; 32%), depression (n = 86; 30%), risk of accidents (n = 68; 23.7%), medical errors (n = 58; 20%) and insomnia (n = 52; 18%).

CONCLUSION

Having to spend 80-90 hours per week in hospitals causes sleep deprivation and negative work performance among doctors. Also, there is anxiety, depression and risk of accidents in their personal lives.

Racial differences in the association between night shift work and melatonin levels among women

Reduced suppression of melatonin in response to working the night shift among people of Asian ancestry has been suggested as a possible explanation for the null results observed in a recent analysis of shift work and breast cancer risk in a Chinese cohort. The authors analyzed the impact of Asian versus white race on previously reported differences in urinary 6-sulfatoxymelatonin levels in a 2003-2008 study in Seattle, Washington, of female health-care workers that exclusively worked night or day shifts. A total of 225 white and 51 Asian participants were included in the analysis. Although 6-sulfatoxymelatonin levels were affected by night shift work in both racial groups, Asian night shift workers consistently showed 6-sulfatoxymelatonin levels that were closer to levels in day shift workers than did white night shift workers. Furthermore, differences in 6-sulfatoxymelatonin levels between white and Asian night shift workers relative to day shift workers were statistically significant in every instance (P < 0.05). These results suggest that Asians may be better able to maintain a "normal" circadian pattern of melatonin production compared with whites and suggest a biological mechanism by which Asian night shift workers may be at a reduced risk of cancer.

The relationship between thermal comfort and light intensity with sleep quality and eye tiredness in shift work nurses

Environmental conditions such as lighting and thermal comfort are influencing factors on sleep quality and visual tiredness. The purpose of this study was the determination of the relationship between thermal comfort and light intensity with the sleep quality and eye fatigue in shift nurses.

METHOD

This cross-sectional research was conducted on 82 shift-work personnel of 18 nursing workstations in Isfahan Al-Zahra Hospital, Iran, in 2012. Heat stress monitoring (WBGT) and photometer (Hagner Model) were used for measuring the thermal conditions and illumination intensity, respectively. To measure the sleep quality, visual tiredness, and thermal comfort, Pittsburg sleep quality index, eye fatigue questionnaire, and thermal comfort questionnaire were used, respectively. The data were analyzed with descriptive statistics, Student's t-test, and Pearson correlation.

RESULTS

Correlation between thermal comfort which was perceived from the self-reporting of people with eye tiredness was -0.38 (P = 0.002). Pearson correlation between thermal comfort and sleep quality showed a positive and direct relationship (r = 0.241, P = 0.33) but the correlation between thermal comfort, which was perceived from the self-reporting of shift nurses, and WBGT index was a weak relationship (r = 0.019).

CONCLUSION

Based on the obtained findings, it can be concluded that a defect in environmental conditions such as thermal conditions and light intensity and also lack of appropriate managerial plan for night shift-work nurses are destructive and negative factors for the physical and mental health of this group of practitioners.

Adaptation to shift work: physiologically based modeling of the effects of lighting and shifts' start time

Shift work has become an integral part of our life with almost 20% of the population being involved in different shift schedules in developed countries. However, the atypical work times, especially the night shifts, are associated with reduced quality and quantity of sleep that leads to increase of sleepiness often culminating in accidents. It has been demonstrated that shift workers’ sleepiness can be improved by a proper scheduling of light exposure and optimizing shifts timing. Here, an integrated physiologically-based model of sleep-wake cycles is used to predict adaptation to shift work in different light conditions and for different shift start times for a schedule of four consecutive days of work. The integrated model combines a model of the ascending arousal system in the brain that controls the sleep-wake switch and a human circadian pacemaker model. To validate the application of the integrated model and demonstrate its utility, its dynamics are adjusted to achieve a fit to published experimental results showing adaptation of night shift workers (n = 8) in conditions of either bright or regular lighting. Further, the model is used to predict the shift workers’ adaptation to the same shift schedule, but for conditions not considered in the experiment. The model demonstrates that the intensity of shift light can be reduced fourfold from that used in the experiment and still produce good adaptation to night work. The model predicts that sleepiness of the workers during night shifts on a protocol with either bright or regular lighting can be significantly improved by starting the shift earlier in the night, e.g.; at 21∶00 instead of 00∶00. Finally, the study predicts that people of the same chronotype, i.e. with identical sleep times in normal conditions, can have drastically different responses to shift work depending on their intrinsic circadian and homeostatic parameters.

Shift work and cancer research: a thought experiment into a potential chronobiological fallacy of past and perspectives for future epidemiological studies

With their 2007 classification - shift work involving "circadian disruption" is probably carcinogenic to humans (Group 2A) - the International Agency for Research on Cancer [IARC] provided a riddle for scientists and the public alike. Thereafter, eighteen epidemiological investigations into shift work and a host of malignant endpoints (including cancers of the breast, prostate, lung, colon, rectum, pancreas, bladder, skin and non-Hodgkin lymphoma [NHL]) as well as mortality were published. Although IARC experts identified "circadian disruption" as the critical link in the "probable" chains of cancer causation, almost none of the post-IARC studies specifically considered a disturbed temporal organization of biology. This implies that epidemiological research to-date is less focused than it should be. To illustrate a potential chronobiological fallacy of past studies, we offer a thought experiment. In addition, we consider first empirical evidence from recent research which avoided such bias. Methodological perspectives for future chronobiology-driven epidemiological research are outlined.

[Influence of work intensity on development of arterial hypertension in metal-mining workers]

The article covers data on influence of working shifts duration and shift work intensity on cardiovascular system functioning in operators of mining excavators. Findings are that 8 hours shift with regular shift schedule (40 working hours per week) gives significant load on cardiovascular system of workers engaged into underground activities. 50% of mining excavator operators following this working schedule develop transitory arterial hypertension within 10 years. Longer work shift over 8 hours and more intensive shifting schedule over 40 hours per week causes stable arterial hypertension within 3 months in 60% of workers, in 10% of cases associated with lower functioning of sinus node.

Psychomotor performance of truck drivers before and after day shifts

OBJECTIVE

The aim of the present study is to evaluate the psychomotor performance of professional drivers in a field setting and in relation to certain variables, including age, behavioral factors, urinary levels of 6-sulfatoxymelatonin (aMT6s) normalized to urinary creatinine excretion, and the characteristics of the work shifts.

METHODS

The study was carried out on 16 professional male truck drivers aged 34-53 years. The drivers were submitted to the Vienna Reaction Test (RT) and Vienna Determination Test (DT) and provided urine specimens before and after 39 work shifts. They were also asked to record the road and traffic conditions (motorways, suburban and urban roads, traffic jams, visibility), duration, and mileage for each driving shift.

RESULTS

Using the 50th percentile as a cut point to arbitrarily categorize the performance measurements (Vienna RT reaction time and motor time, Vienna DT reaction time and number of correct reactions) into low and high performance levels, a direct relation emerged between the risk of low performance levels, as assessed by RT reaction time and motor time, and morning urinary levels of aMT6s categorized by tertiles. Before the driving shifts, the odds ratios of low performance levels (adjusted for start time and age) were 8.39 (95% confidence interval [CI]: 1.23-57.10) in the highest tertile compared to the lower tertile of aMT6s for RT reaction time and 4.15 (95% CI: 1.26-13.65) for RT motor time, respectively. After driving shifts, negative age-related effects on motor performance were detected. Multiple linear regression analyses, performed using early morning urinary aMT6s levels, age, and driving shift characteristics (start time, duration of driving shift) as predictors of performance measurements, showed aMT6s levels to be the primary independent predictor of RT reaction time before driving shifts and age as the primary predictor of RT motor time after driving shifts. No correlation was found between the risk of low performance levels as assessed by Vienna DT (reaction time and number of correct reactions) and aMT6s levels.

CONCLUSIONS

The wide interindividual variability of urinary aMT6s excretion observed before driving shifts and the direct association between aMT6s levels in the early morning and performance measurements suggest that the circadian typology of drivers should be taken into account when scheduling the work shifts of professional drivers.

[Diurnal blood pressure profiles in night shift workers with incipient changes of blood pressure level]

Aim. To study diurnal blood pressure profiles (DBPP) during work in different time of the day including nocturnal hours in persons with initial stages of blood pressure (BP) increase or decrease. Material and methods. The study cohort consisted of 995 locomotive drivers (46682 BP measurements) divided into groups with normal BP, higher normal BP, 1st stage arterial hypertension, and hypotension. DBPP was analyzed on the basis of the averaged curve for each group. Results. The averaged systolic DBPP in the normotonic group was of non-dipper type, while diastolic one was on the border between non-dipper and night-peaker. Patients with elevated BP and trend to BP elevation (beginning with higher normal BP) had reduced nocturnal BP lowering, particularly of diastolic BP. Its diurnal profile was clearly of night-peaker type. The main feature of DBPP in patients with hypotension was absence of evening BP rise characteristic for persons with normal BP and hypertension.

Fatigue in seafarers working in the offshore oil and gas re-supply industry: effects of safety climate, psychosocial work environment and shift arrangement

This study examined the influence of safety climate and psychosocial work environment on the reported fatigue of seafarers working in the offshore oil and gas re-supply industry (n = 402). We found that seafarers who reported high psychological demands and perceived the organisational-level safety climate negatively,reported significantly more mental fatigue, physical fatigue, and lack of energy. In addition, seafarers who reported having high levels of job control reported being significantly less mentally fatigued. We also found some combined effects of safety climate and shift arrangement. Organisational-level safety climate did not influence the levels of physical fatigue in seafarers working on the night shift. On the contrary, seafarers working during the days reported to be more physically fatigued when they perceived the organisational-level climate to be negative compared with the positive. The opposite effect was found for group-level safety climate: seafarers working during the nights reported to be more physically fatigued when they perceived the group-level climate to be negative compared with the positive. The results from this study point to the importance of taking into consideration aspects of the psychosocial work environment and safety climate,and their potential impact on fatigue and safety in the maritime organisations.

[Night work and health of nurses and midviwes--a review]

Night shift work has been thought to play a role in the etiology of chronic diseases through a disruption of the circadian rhythm, decreased synthesis of melatonin and sleep deprivation. Our aim was to review the epidemiological studies on the association between night shift work and some pathologies in nurses and midwives. We reviewed publications available in the MEDLINE database and published before June 2012, describing the cross-sectional (almost two thirds of all papers) and cohort studies. In total, we identified 26 original papers, including 5 epidemiological studies addressing diseases or disorders of the digestive system, 3--metabolic syndrome, 2--type 2 diabetes, 9--cardiovascular diseases and (CVD risk factors, 5--obesity/overweight, 2--menstrual disorders and 3--poor pregnancy outcomes. The analysis of the literature indicates that night shift work of nurses and midwives is most strongly associated with a higher risk ofobesity/overweight. In each of the five studies, which we identified this association was observed (confirmed by the statistical significance of the results), also after adjustment for confounders. The results for type 2 diabetes and disorders of the menstrual cycle are also suggestive. Epidemiological data on the other disorders or pathologies discussed in this article seem to be less certain - their results are inconsistent or their number is too small to draw definite conclusions. Further epidemiological studies of nurses and midwives working on night shifts and prospective observations in particular are recommended to find out whether potential association between the night work and discussed health issues is causal.

[Diurnal blood pressure rhythms in night shift workers in terms of age and work experience: issues of adaptation]

The circadian rhythms of blood pressure (BP) are studied in working persons within every hour of day and night by the means of multipoint measurements of BP in pre-shift period. The analysed cohort consists of 34 163 locomotive drivers (544 804 individual BP measurement points). Basing on these data the average diurnal BP profiles (DPBP) are plotted for different age and work experience groups. It is established that all DPBPs are of non-dipper type. This can be considered as a mechanism of adaptation being a compromise between work requirements and minimization of health hazard. This kind of adaptation develops approximately in one year period.

Working conditions and major weight gain-a prospective cohort study

The objective of this study was to examine the associations of working conditions with major weight gain. Three different groups of work-related factors were examined: (i) work arrangements, (ii) physical working conditions, and (iii) psychosocial working conditions. The data are based on the Helsinki Health Study (HHS) questionnaire surveys. A baseline mail survey was made among middle-aged employees of the City of Helsinki in 2000-2002. A follow-up survey was made in 2007. Regression analyses with odds ratios and 95% confidence intervals were calculated. During the 5- to 7-year follow-up, 26% of women and 24% of men gained in weight 5 kg or more. Working conditions were mostly unassociated with weight gain. However, nighttime shift work, physical threat at work, and hazardous exposures at work were moderately associated with weight gain. More attention should be devoted to the prevention of weight gain in general and among risk groups in particular.

Differences in heart rate variability of female nurses between and within normal and extended work shifts

The aim of this study was to investigate differences in heart rate variability (HRV) reflecting the function of autonomic nervous system (ANS) and psycho-physiological strain associated with normal and extended work shifts in nursing work. Complete data were available from 51 female nurses with a mean age of 40 yr, and based on two comparable 36-h HRV measurements supplemented with a questionnaire. Time-domain (meanRR, SDNN, RMSSD) and frequency-domain (LF power, HF power) parameters represented the HRV data, and were analyzed by linear mixed models. The differences between the compared work shifts were minor, revealing mainly increased sympathetic activity at the beginning of the normal work shift. The HRV parameters detected significant differences between work and leisure-time during the normal and extended work shifts in female nurses. During work shifts, an increase in sympathetic and a decrease in parasympathetic control of HRV was observed when compared to the leisure-time situation. Older subjects had overall lower HRV than younger subjects indicating increased sympathetic activation of ANS, especially during work. HRV parameters revealed significant differences between work, leisure-time and sleep of female nurses, but there were few differences between normal and extended work shifts in HRV parameters. This lack of differences between work shifts may be a consequence of the adaptation of nurses to the extended shifts or the more flexible organization of work duties possible during extended work shifts.

Relationship between intensity of night shift work and antioxidant status in blood of nurses

Purpose

Light-at-night exposure can disrupt the human circadian rhythm via clock gene expressions. The circadian rhythm influences antioxidant enzymes’ activity and cellular mRNA levels of these enzymes. The employees working based on a shift system adjust to the changes occurring both on the cell level and on the level of the whole organism. Therefore, a question should be answered whether shift work disturbs oxidant–antioxidant balance and/or generates oxidative stress.

Methods

A cross-sectional study was conducted among nurses selected from the Local Registry of the Chamber of Nurses and Midwives in Lodz: 359 nurses worked daily only and 349 working rotating night shifts. These two groups differed significantly in respect of age (p < 0.0001), menopausal status (p < 0.0001), and current smoking habit (p = 0.02). The average total work duration was significantly shorter (12.4 years) in nurses working currently rotating night shifts who worked significantly longer on night shifts than day-workers (26.6 years).

Results

We found statistically significant higher red blood cell glutathione peroxidase in nurses working on night shifts (21.0 ± 4.6 vs. 20.0 ± 5.0 U/g Hb, p < 0.009) after adjusting for age, oral contraceptive hormone use, smoking, and drinking alcohol during last 24 h. Statistically significant lower vitamin A and E levels were found in the premenopausal women working in rotating system (0.690 ± 0.238 vs. 0.786 ± 0.262 μg/ml, p < 0.0001 for vitamin A and 10.93 ± 4.15 vs. 12.78 ± 4.75 μg/ml, p < 0.0001 for vitamin E). The marker of lipid peroxidation (TBARS concentration) was significantly lower in the premenopausal nurses than postmenopausal ones working day shifts only (2.06 ± 0.76 vs. 2.21 ± 0.80 nmol/ml, p < 0.038). We observed that erythrocyte GSH-Px activity rose statistically significant in nurses working more night shifts per month (p < 0.01).

Conclusions

The results quoted above seem to support the existence of an association between light-at-night exposure and blood glutathione peroxidase activity in female shift workers. Nevertheless, in order to explain the mechanisms of this association, we need more studies.

Associations of long-term shift work with waking salivary cortisol concentration and patterns among police officers

The objective of this study was to evaluate whether long-term shift work is associated with both the total hormonal secretion after awakening and the pattern of the cortisol levels during the first hour following awakening, among 65 randomly selected police officers who represent a high stress occupation. Dominant shift (Day, Afternoon, or Midnight) was ascertained using daily payroll records of each participant's work activities during the 6-8 yrs prior to saliva sampling. Four salivary samples were collected at 15 min intervals upon first awakening. After accounting for potential confounders, salivary cortisol concentrations averaged across all four time points and total area under the curve differed significantly across shift with midnight shift workers showing suppressed awakening cortisol response relative to the afternoon and day shift. The percent of hours worked on midnight shift was inversely correlated with total awakening cortisol output. In contrast, the pattern of cortisol secretion during the first hour following waking appeared not to be affected as no significant interaction effect was found between time since awakening and shift work. The results show that long-term midnight shift work is associated with decreased absolute mean level and total volume of cortisol released over the waking period.

[Night shift and the risk of hormone-dependent diseases in women]

From cards of follow-up of industrial contingent passing preventive medical examinations, the frequency of disorders of the reproductive sphere and the endocrine system in 208 women employed in shift work including the night shift was investigated in comparison with 102 female members of administrative and managerial staff The relative risk (RR) of all investigated pathologies associated with employment in night shifts, was 1.52 (95% confidence interval (CI): 1.06-2.18). The increased risk of mastitis (OR = 1.13, 95% CI 0.95-1.35), and a uterine myoma (RR = 1.16, 95% CI: 1.00-1.36) was on the border of statistical significance. Endometriosis was significantly more frequent in the study group: RR = 1.23 (1.04-1.45). The risk of developing ovarian cysts was not significantly lower: RR = 0.94 (95% CI: 0.72-1.24). In connection with the employment in night shifts increased risk of all endocrine diseases was observed on the border of statistical significance: RR = 1.18 (95% CI: 0.99-1.40), including the development of obesity: RR = 1.22 (95% CI 1.05-1.43). The frequency of diabetes in the group of workers with night shifts was statistically significantly higher (OR = 1.13, 95% CI: 0.84-1.51). The pathology of the thyroid gland in the study group occurred less frequently than in the control one: RR = 0.88 (95% CI: 0.73-1.07). These data are preliminary, but they are consistent with the available experimental and epidemiological data.

Sleep and circadian rhythms in mining operators: limited evidence of adaptation to night shifts

Cumulative sleep deprivation is often associated with work patterns involving night shift or early morning shifts. Adaptation of the circadian system to the shift pattern is reported to promote improved duration and quality of sleep and a concurrent improvement in performance. The current study followed twenty-nine operators at a live-in mining operation working to a seven-day, seven-night shift pattern who collected saliva samples for melatonin measurement, recorded sleep using activity monitors and diaries, and underwent performance testing (psychomotor vigilance task) for one complete roster cycle. The time of onset of melatonin secretion changed significantly (P=0.022) across the week of both Day and Night shifts (2104 h ± 16 min versus 2130 h ± 16 min, respectively), but the small magnitude of the change indicates a lack of true circadian rhythm adaptation to the lifestyle. Total sleep time was longer following the seventh Day shift (associated with a period of 24 h off prior to the commencement of Night shifts). There were no other changes in total sleep time. Further, there were no improvements in sleep onset latency or sleep efficiency on Day or Night shifts. However, reaction times recorded at the end of the shifts slowed across the seven Day and seven Night shifts indicative of impairments in psychomotor performance (F(6,168)=6.087, P<0.001). The results suggest that previous reports of adaptation to consecutive night shifts cannot necessarily be applied to onshore or Australian environments. Adaptation is dependent on factors such as light exposure, environmental conditions, shift parameters such as wake-up, work start and work end times and individual characteristics.

Attenuation of vagal recovery during sleep and reduction of cortisol/melatonin ratio in late afternoon associate with prolonged daytime sleepiness among media workers with irregular shift work

BACKGROUND

Media work is characterized by information flow, deadlines, and 24/7 alertness. Good recovery prevents stress-related disorders.

METHODS

The standardized questionnaire included items about health, health habits, sleep, work conditions, and work stress. Recordings of 24-hr heart rate variability (HRV) and four salivary samples for cortisol and melatonin levels were analyzed from 70 randomly selected workers with irregular shift work, and 70 workers with normal daytime work.

RESULTS

Irregular shift work increased the risk of insufficient recovery when compared to normal daytime work (OR 2.0; P < 0.05). In the group of workers with insufficient subjective recovery, HRV was attenuated (P < 0.05) during the early hours of night, and cortisol/melatonin ratio was decreased (P < 0.05) in the afternoon.

CONCLUSIONS

Physiological changes underlying subjective feelings of insufficient recovery are measurable. Attenuated HRV during sleep reflects prolonged sympathetic drive and/or impaired parasympathetic recovery. Interactions between cortisol and melatonin hormones might be involved in the development of chronic exhaustion.

[Effect of intensive 24-hour shift work on reliability of operators' activity]

Psychophysiological peculiarities of the effect of 24-hour shift work on psychophysiological indices of an operator's efficiency have been considered. It is found that significant manifestations of the fatigue have been developed in servicemen-operators as a result of daily shift-work. The informative psychophysiological characteristics, which can be used as reliable indicators of fatigue level, have been distinguished. A hypothesis has been proposed on the availability of several compensatory mechanisms in maintenance of the work capacity in operators in long-term shift work. An integral index of the reliability of operators' activity has been developed, allowing to assess the quality of work, using a wide range of intensities of the proposed signals as well as to receive data on the overall possibilities of an operator to process information at the given level of reliability.

Effect of exposure to occupational noise and shift working on blood pressure in rubber manufacturing company workers

This study aimed to assess the relationship between shift working and occupational exposure to noise with blood pressure (BP). The study was carried out in a rubber manufacturing company in 2010. Demographic, medical and occupational information for carrying out the study were collected through direct interview. All 331 under study workers were divided into four groups according to work shift and noise exposure severity, from non-noise exposed day time workers (Group 1) to noise exposed shift workers (Group 4). Finally, systolic and diastolic blood pressure levels were compared among these four groups. The results of this study showed that there was a significant difference between average systolic and diastolic BP and hypertension (HTN) frequency in the four groups (p<0.05). The highest rate of HTN and mean systolic and diastolic BP were observed among shift workers who were exposed to noise higher than permissible limit (Group 4). Also the results of logistic regression analysis showed that there was a significant relationship between simultaneous exposures to noise more than the permitted limit and shift work with HTN (p<0.05). The results of our study showed that shift working and simultaneous exposure to noise have an additive effect on occurrence of HTN. It is recommended that during periodic physical examinations of noise exposed shift workers, assessment of the cardiovascular system and BP should be done as well as the auditory system.

Prioritizing sleep for healthy work schedules

Good sleep is advantageous to the quality of life. Sleep-related benefits are particularly helpful for the working class, since poor or inadequate amounts of sleep degrade work productivity and overall health. This review paper explores the essential role of sleep in healthy work schedules and primarily focuses on the timing of sleep in relation to the work period (that is, before, during and after work). Data from laboratory, field and modeling studies indicate that consistent amounts of sleep prior to work are fundamental to improved performance and alertness in the workplace. In addition, planned naps taken during work maintain appropriate levels of waking function for both daytime and night-time work. Clearly, sufficient sleep after work is vital in promoting recovery from fatigue. Recent data also suggest that the time interval between shifts should be adjusted according to the biological timing of sleep. Although sleep is more likely to be replaced by job and other activities in the real life, research shows that it is worthwhile to revise the work schedules in order to optimize sleep before, sometime during and after the work period. Therefore, we suggest establishing work-sleep balance, similar to work-life balance, as a principle for designing and improving work schedules.

Simulated driving under the influence of extended wake, time of day and sleep restriction

Around a fifth of all road accidents can be attributed to fatigued drivers. Previous studies indicate that driving performance is influenced by time of day and decreases with sustained wakefulness. However, these influences occur naturally in unison, confounding their effects. Typically, when people drive at a poor time of day and with extended wake, their sleep is also restricted. Hence, the aim of the current study was to determine the independent effects of prior wake and time of day on driving performance under conditions of sleep restriction. The driving performance of fourteen male participants (21.8 ± 3.8 years, mean ± SD) was assessed during a 10 min simulated driving task with speed/lane mean, variability and violations (speeding and crashes) measured. Participants were tested at 2.5h intervals after waking, across 7 × 28 h days with a sleep:wake ratio of 1:5. By forced desynchrony each driving session occurred at 9 doses of prior wake and within 6 divisions of the circadian cycle based on core body temperature. A mixed models ANOVA revealed significant main effects of circadian phase, prior wake and sleep debt on lane violations. In addition, three significant two-way interactions (circadian phase × prior wake, prior wake × sleep debt, sleep debt × circadian phase) and one three-way interaction (circadian × prior wake × sleep debt) were identified. The presence of the large interaction effects shows that the influence of each factor is largely dependent on the magnitude of the other factors. For example, the presence of the time of day influence on driving performance is dependent on the length of prior wake or the presence of sleep debt. The findings suggest that people are able to undertake a low-difficulty simulated drive safely, at least for a short period, during their circadian nadir provided that they have had sufficient sleep and have not been awake too long.

Can a simple balance task be used to assess fitness for duty?

Human fatigue, caused by sleep loss, extended wakefulness, and/or circadian misalignment, is a major cause of workplace errors, incidents and accidents. In some industries, employees are required to undertake fitness for duty testing at the start of a shift to identify instances where their fatigue risk is elevated, so that minimisation and/or mitigation strategies can be implemented. Postural balance has been proposed as a fitness for duty test for fatigue, but it is largely untested. Therefore, the purpose of this study was to examine the impact of sleep loss, extended wakefulness and circadian phase on postural balance. Fourteen male participants spent 10 consecutive days in a sleep laboratory, including three adaptation days and eight simulated shiftwork days. To simulate a quickly rotating roster, shiftwork days were scheduled to begin 4h later each day, and consisted of a 23.3-h wake episode and a 4.7-h sleep opportunity. Every 2.5h during wake, balance was measured while standing as still as possible on a force platform with eyes open for one minute, and eyes closed for one minute. Subjective sleepiness was assessed using the Karolinska Sleepiness Scale. Core body temperature, continuously recorded with rectal thermistors, was used to determine circadian phase. For measures of postural balance and subjective sleepiness, data were analysed using three separate repeated measures ANOVA with two within-subjects factors: circadian phase (six phases) and prior wake (nine levels). For subjective sleepiness, there was a significant effect of prior wake and circadian phase. In particular, sleepiness increased as prior wake increased, and was higher during biological night-time than biological daytime. For the eyes open balance task, there was no effect of prior wake or circadian phase. For the eyes closed balance task, there was a significant effect of circadian phase such that balance was poorer during the biological night-time than biological daytime, but there was no effect of prior wake. These results indicate that postural balance may be a viable tool for assessing fatigue associated with time of day, but may not be useful for assessing fatigue associated with extended hours of wake.

Sleep and sleepiness during an ultra long-range flight operation between the Middle East and United States

This study provides a practical example of fatigue risk management in aviation. The sleep and sleepiness of 44 pilots (11 trips × 4 pilot crew) working an ultra long-range (ULR; flight time >16 h) round-trip operation between Doha and Houston was assessed. Sleep was assessed using activity monitors and self-reported sleep diaries. Mean Karolinska Sleepiness Scores (KSS) for climb and descent did not exceed 5 ("neither alert nor sleepy"). Mean daily sleep duration was maintained above 6.3h throughout the operation. During in-flight rest periods, 98% of pilots obtained sleep and sleepiness was subsequently reduced. On layover (49.5h) crew were advised to sleep on Doha or Universal Co-ordinated Time (UTC), but 64% slept during the local (social) night time. Pilots originating from regions with a siesta culture were more likely to nap and made particularly effective use of their daytime in-flight rest periods. The results indicate that the operation is well designed from a fatigue management perspective.

Beyond working time: factors affecting sleep behaviour in rail safety workers

There are many factors that may affect the sleep behaviour and subsequent fatigue risk of shift workers. In the Australian rail industry the emphasis is primarily on the impact of working time on sleep. The extent to which factors other than working time might affect the sleep behaviour of employees in the large and diverse Australian rail industry is largely unknown. The present study used sleep, work and fatigue diaries completed for two weeks, in conjunction with actigraphy, to understand the contribution of demographic and health factors to sleep behaviour in 40 rail safety workers. Both shift type and having dependents were significant predictors of sleep duration (P<.05). Sleep duration was greatest prior to night shifts, followed by afternoon shifts and morning shifts. Participants with dependents got significantly less sleep than participants without dependents. Both timing of sleep and smoking were significant predictors of sleep quality (P<.05). Day sleeps were associated with lower subjective sleep quality than night sleeps and smokers reported poorer sleep quality than non-smokers. These findings indicate that factors other than working time have the potential to influence both the sleep duration and subjective sleep quality of rail safety workers.

At home and away: measuring the sleep of Australian truck drivers

The causes of fatigue in truck drivers related to work hours have been studied extensively and are reasonably well understood. However, much less is known about how rest opportunities can be structured to optimise recovery from fatigue. The nature of the road transport industry often requires that rest be taken in various locations. New investigation in this area, focusing on sleep obtained in truck cabs and other non-home environments is critically important to complement existing understanding. This study examined sleep at home and in truck cabs, in truck drivers who were actively working during the time of the study. Thirty-seven male drivers aged between 24 and 63 years (age: 48.7 ± 9.0 years; mean ± SD) wore activity monitors (also known as 'sleep watches') and completed work and sleep diaries for a period of 21 days, recording their subjective fatigue levels before, during and after work shifts, and before and after sleep periods. They also self-rated their sleep quality and noted the number of times they woke during sleep periods. Analyses focused on home versus in-truck sleep periods. The subjective data suggested that a greater quantity (P<.001) and quality (P<.05) of sleep was obtained at home than in the truck, and that sleeping at home more effectively reduced fatigue levels (P<.001). The objective data showed trends towards longer sleep length at home, but other variables, including total sleep per 24h and sleep quality, showed no significant differences. This study demonstrates that measuring sleep quantity and quality in operational road transport environments is feasible. The findings caution against over-reliance on laboratory and simulator studies since there are critical aspects of the operating environment that cannot be validly studied in artificially controlled settings. This study is unique in its direct examination of sleep quantity and quality in truck drivers sleeping at home and away from home.

Duty periods with early start times restrict the amount of sleep obtained by short-haul airline pilots

Most of the research related to human fatigue in the aviation industry has focussed on long-haul pilots, but short-haul pilots also experience elevated levels of fatigue. The aim of this study was to examine the impact of early start times on the amount of sleep obtained prior to duty and on fatigue levels at the start of duty. Seventy short-haul pilots collected data regarding their duty schedule and sleep/wake behaviour for at least two weeks. Data were collected using self-report duty/sleep diaries and wrist activity monitors. Mixed-effects regression analyses were used to examine the effects of duty start time (04:00-10:00 h) on (i) the total amount of sleep obtained in the 12h prior to the start of duty and (ii) self-rated fatigue level at the start of duty. Both analyses indicated significant main effects of duty start time. In particular, the amount of sleep obtained in the 12h prior to duty was lowest for duty periods that commenced between 04:00 and 05:00 h (i.e. 5.4h), and greatest for duty periods that commenced between 09:00 and 10:00 h (i.e. 6.6h). These data indicate that approximately 15 min of sleep is lost for every hour that the start of duty is advanced prior to 09:00 h. In addition, self-rated fatigue at the start of duty was highest for duty periods that commenced between 04:00 and 05:00 h, and lowest for duty periods that commenced between 09:00 and 10:00 h. Airlines should implement a fatigue risk management system (FRMS) for short-haul pilots required to work early-morning shifts. One component of the FRMS should be focussed on the production of 'fatigue-friendly' rosters. A second component of the FRMS should be focussed on training pilots to optimise sleep opportunities, to identify circumstances where the likelihood of fatigue is elevated, and to manage the risks associated with fatigue-related impairment.

Predicting pilot's sleep during layovers using their own behaviour or data from colleagues: implications for biomathematical models

Biomathematical models are used in industry to estimate how much sleep people are likely to get on different work patterns, and how efficient and safe people are likely to be at work. Since there is evidence to suggest that individuals respond differently to sleep loss, there has been a recent focus on trying to account for individual differences. One possible approach could use past behaviour to predict future responses to similar working conditions. This study investigated the predictive value of sleep timing and duration data for a particular individual on a break between shifts relative to data from their colleagues. Sleep diaries and wrist actigraphy were collected from 306 international long-haul pilots for at least 2-weeks. Fifty layovers, equivalent in origin and destination, length and timing, were completed twice by individual pilots. Matched layovers done by other pilots (n=2311) were also identified. Layover periods were analysed for minute-by-minute correspondence of sleep or wake (yes/no), and total sleep time (TST). Using an individual's own data improved concordance by approximately 5% relative to using a large sample of different pilots, and by 10% relative to using a random sample of 50 different pilots. Using an individual's own TST to predict their TST on an equivalent layover yielded an r value of 0.83, compared to r=0.78 when data from a colleague was used, and r=0.73 using different pilots in a random sample of equivalent size. The mean difference in TST using pilots' own data was <20 min, compared to <40 min using data from colleagues. However, the confidence limits on these differences were large (up to 8h). Results suggest that for international pilots on specific layover patterns, knowing the past behaviour of an individual may only represent a modest improvement over knowing the length and timing of a colleague's sleep, when it comes to predicting their sleep behaviour.

Restricted sleep and negative affective states in commercial pilots during short haul operations

This study aims to investigate (1) the relationship between restricted sleep and Heightened Emotional Activity (HEA) during normal flight operations, and (2) whether sleep patterns influence the strength of the HEA as a response to threats. Accident investigation reports continue to highlight the relationship between restricted sleep and poor safety outcomes. However, to date we have a limited understanding of how sleep and HEA interact. A total of 302 sectors of normal airline flight operations were observed by trained observers, and instances of heightened emotional activity were recorded. During the cruise phase of each of these sectors, crew members were asked to calculate the amount of sleep they had obtained in previous 24 and 48 h. In the 302 sectors of normal flight operations, 535 instances of HEA were observed. Descriptive analyses of instances of HEA and sleep in the prior 24 and 48 h showed a significant relationship between the occurrence of HEA and recent sleep. The relationship between restricted sleep and HEA suggests that there may well be further implications with respect to operational safety.

The effect of sleep restriction on snacking behaviour during a week of simulated shiftwork

Due to irregular working hours shiftworkers experience circadian disruption and sleep restriction. There is some evidence to indicate that these factors adversely affect health through changes in snacking behaviour. The aim of this study was to investigate the impact of sleep restriction, prior wake and circadian phase on snacking behaviour during a week of simulated shiftwork. Twenty-four healthy males (age: 22.0 ± 3.6 years, mean ± SD) lived in a sleep laboratory for 12 consecutive days. Participants were assigned to one of two schedules: a moderate sleep restriction condition (n=10) equivalent to a 6-h sleep opportunity per 24h or a severe sleep restriction condition (n=14) equivalent to a 4-h sleep opportunity per 24h. In both conditions, sleep/wake episodes occurred 4h later each day to simulate a rotating shiftwork pattern. While living in the laboratory, participants were served three meals and were provided with either five (moderate sleep restriction condition) or six (severe sleep restriction condition) snack opportunities daily. Snack choice was recorded at each opportunity and assigned to a category (sweet, savoury or healthy) based on the content of the snack. Data were analysed using a Generalised Estimating Equations approach. Analyses show a significant effect of sleep restriction condition on overall and sweet snack consumption. The odds of consuming a snack were significantly greater in the severe sleep restriction condition (P<0.05) compared to the moderate sleep restriction condition. In particular, the odds of choosing a sweet snack were significantly increased in the severe sleep restriction condition (P<0.05). Shiftworkers who are severely sleep restricted may be at risk of obesity and related health disorders due to elevated snack consumption and unhealthy snack choice. To further understand the impact of sleep restriction on snacking behaviour, future studies should examine physiological, psychological and environmental motivators.

Night-shift work and cardiovascular risk among employees of a public university

OBJECTIVE

To estimate the association between night-shift work and high cardiovascular risk.

METHODS

Cross-sectional study carried out with 211 workers of both genders, aged between 30 and 64 years, working on the health campus of a public university in the state of Minas Gerais, Brazil. Night-shift work was defined as a work shift between 7 pm and 7 am, and high cardiovascular risk was calculated based on the Framingham score. The association between night-shift work and high cardiovascular risk was estimated by the prevalence ratio (PR) and its 95% confidence interval (95% CI) after adjusting for potential confounding factors, calculated by Poisson regression.

RESULTS

Night-shift work was performed by 38.4% of the individuals, and high cardiovascular risk was diagnosed in 28% of the sample. Hypertension was more prevalent among night-shift compared with day-shift workers (p < 0.05). In the bivariate analysis, night-shift work, passive and high job strain categories at the demand-control scale, work time > 120 months, schooling > 9 years, family income > 6 minimum wages, level 2 abdominal obesity, and triglyceride levels > 150 mg/dL were associated with high cardiovascular risk (p < 0.05). After multivariate analysis, night-shift work remained independently associated with high cardiovascular risk (PR = 1.67; 95% CI = 1.10-2.54).

CONCLUSION

The prevalence of high cardiovascular risk was 67% higher among night-shift workers. This association should be considered when discussing the promotion of workers' health regarding changes in the work process.

Research and guidelines for implementing Fatigue Risk Management Systems for the French regional airlines

This paper describes research that aims to provide the overall scientific basis for implementation of a Fatigue Risk Management System (FRMS) for French regional airlines. The current research has evaluated the use of different tools and indicators that would be relevant candidates for integration into the FRMS. For the Fatigue Risk Management component, results show that biomathematical models of fatigue are useful tools to help an airline to prevent fatigue related to roster design and for the management of aircrew planning. The Fatigue Safety assurance includes two monitoring processes that have been evaluated during this research: systematic monitoring and focused monitoring. Systematic monitoring consists of the analysis of existing safety indicators such as Air Safety Reports (ASR) and Flight Data Monitoring (FDM). Results show a significant relationship between the hours of work and the frequency of ASR. Results for the FDM analysis show that some events are significantly related to the fatigue risk associated with the hours of works. Focused monitoring includes a website survey and specific in-flight observations and data collection. Sleep and fatigue measurements have been collected from 115 aircrews over 12-day periods (including rest periods). Before morning duties, results show a significant sleep reduction of up to 40% of the aircrews' usual sleep needs leading to a clear increase of fatigue during flights. From these results, specific guidelines are developed to help the airlines to implement the FRMS and for the airworthiness to oversight the implementation of the FRMS process.

Patterns of salivary cortisol levels can manifest work stress in emergency care providers

To develop objective assessments of work fatigue, we investigated the patterns of changes in salivary cortisol levels in emergency care providers working extended work shifts. Fourteen subjects, comprising seven physicians and seven physician assistants, provided unstimulated saliva samples at regular intervals over the course of a 24-h work shift and over their subsequent free day. There was a significant time effect, with early morning cortisol levels being significantly attenuated following the work shift. Native diurnal variations varied by gender, with the female subjects manifesting greater cortisol levels. Physicians also had higher cortisol profiles even though their wake-rest cycles were similar to those of the physician assistants. Our results suggest that temporal changes, as well as diurnal similarities, in the salivary cortisol patterns can reflect work-related stress and recovery. In particular, early morning cortisol levels may manifest individual reactivity to work stressors as well as sleep deprivation.

Circadian system, sleep and endocrinology

Levels of numerous hormones vary across the day and night. Such fluctuations are not only attributable to changes in sleep/wakefulness and other behaviors but also to a circadian timing system governed by the suprachiasmatic nucleus of the hypothalamus. Sleep has a strong effect on levels of some hormones such as growth hormone but little effect on others which are more strongly regulated by the circadian timing system (e.g., melatonin). Whereas the exact mechanisms through which sleep affects circulating hormonal levels are poorly understood, more is known about how the circadian timing system influences the secretion of hormones. The suprachiasmatic nucleus exerts its influence on hormones via neuronal and humoral signals but it is now also apparent that peripheral tissues contain circadian clock proteins, similar to those in the suprachiasmatic nucleus, that are also involved in hormone regulation. Under normal circumstances, behaviors and the circadian timing system are synchronized with an optimal phase relationship and consequently hormonal systems are exquisitely regulated. However, many individuals (e.g., shift-workers) frequently and/or chronically undergo circadian misalignment by desynchronizing their sleep/wake and fasting/feeding cycle from the circadian timing system. Recent experiments indicate that circadian misalignment has an adverse effect on metabolic and hormonal factors such as circulating glucose and insulin. Further research is needed to determine the underlying mechanisms that cause the negative effects induced by circadian misalignment. Such research could aid the development of novel countermeasures for circadian misalignment.

Circadian nature of immune function

The primary physiological role of the circadian system is to synchronize and coordinate organ systems, particularly in response to dynamics in the environment. The immune system is under direct circadian control by systemic cues and molecular clocks within immune cells. The master circadian pacemaker called the suprachiasmatic nucleus (SCN) conveys timing information to the immune system through endocrine and autonomic pathways. These signals promote phase coherence of peripheral clocks in the immune system, and also govern daily variations in immune function. The coordination of immune response may compose an anticipatory state for optimal immune response. Interactions between circadian and immune systems are bidirectional, in that immune factors can modulate phasing of circadian clocks. Circadian disruption, such as environmental desynchronization and/or anomalous molecular clock functions, may lead to lack of system coordination, and particular vulnerabilities to infection and disease may develop.

12-h or 8-h shifts? It depends

Since 12-h shifts were first implemented, the question has been asked - are 'twelves' better than 'eights'? People trying to answer this question invariably refer to the limited literature at their disposal, often piecemeal, small-scale studies comparing 8-h versus 12-h shifts in isolated groups of workers in which many other factors vary concurrently. The narrow perspective and sometimes 'vested interests' of the organizations, researchers, publishers and individual workers can influence both the choice of measures, the analysis of results and their interpretation. The current review suggests that it is not sufficient to evaluate a shift pattern on the basis of a single dimension of a working time arrangement, such as shift length. Numerous factors associated with the work practice influence the outcome of a shift pattern including start times, pattern of shifts and amount of overtime. Moreover, the type of work being done and the demographics or characteristics of the workforce are additional mediating factors. Finally, and perhaps most critically, the relative importance assigned to different outcome measures is an important consideration. There are situations where total sleep time might increase following a change to 12-h shifts, whereas domestic life for some workers may deteriorate. Additionally, safety measures may show improvements on 8-h shifts but physical or psychological health outcomes may be worse. The myriad combinations of work pattern, work task, worker and outcome measure under investigation mean that the best way to take account of these complexities may be to use an approach that manages 'system' risk. Given the non-linearities in the system, and the fact that current approaches either ignore, or privilege a subset of outcomes, it is perhaps more appropriate to conceptualize working time arrangements as an 'ecosystem' and to address the risks in the overall system as opposed to a single dimension such as shift length.

[Blood pressure in night shift workers: circadian rhythms and levels, and their seasonal variation]

Average diurnal blood pressure (BP) profiles (DBPP) were studied in persons working at different hours of a day, including night workers. The results obtained in winter and summer seasons were compared. The study consisted of more than 497 000 pre-work BP measurement points for each of 30 566 locomotive drivers. It was found that average DBPP of persons working at different hours of a day is of the marked non-dipper type in spite of night wakefulness. BP was lower at night but not as low as that of night sleeping persons. In the cohort studied, the form of DBPP curve does not differ in winter and summer; however BP in winter is significantly higher.

Job strain and shift work influences on biomarkers and subclinical heart disease indicators: a pilot study

This pilot study is one of the first to examine the impact of job strain and shift work on both the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis using two salivary stress biomarkers and two subclinical heart disease indicators. This study also tested the feasibility of a rigorous biological sampling protocol in a busy workplace setting. Paramedics (n = 21) self-collected five salivary samples over 1 rest and 2 workdays. Samples were analyzed for α-amylase and cortisol diurnal slopes and daily production. Heart rate variability (HRV) was logged over 2 workdays with the Polar RS800 Heart Rate monitors. Endothelial functioning was measured using fingertip peripheral arterial tonometry. Job strain was ascertained using a paramedic-specific survey. The effects of job strain and shift work were examined by comparing paramedic types (dispatchers vs. ambulance attendants) and shift types (daytime vs. rotating day/night). Over 90% of all expected samples were collected and fell within expected normal ranges. Workday samples were significantly different from rest day samples. Dispatchers reported higher job strain than ambulance paramedics and exhibited reduced daily alpha-amylase production, elevated daily cortisol production, and reduced endothelial function. In comparison with daytime-only workers, rotating shift workers reported higher job strain, exhibited flatter α-amylase and cortisol diurnal slopes, reduced daily α-amylase production, elevated daily cortisol production, and reduced HRV and endothelial functioning. Despite non-statistically significant differences between group comparisons, the consistency of the overall trend in subjective and objective measures suggests that exposure to work stressors may lead to dysregulation in neuroendocrine activity and, over the long-term, to early signs of heart disease. Results suggest that further study is warranted in this population. Power calculations based on effect sizes in the shift type comparison suggest a study size of n = 250 may result in significant differences at p = 0.05. High compliance among paramedics to complete the intensive protocol suggests this study will be feasible in a larger population.

[Preventing hazardous effects of work on functional state of mental workers]

Long-standing research covered hazardous effects of intense work on functional state of mental workers. Findings are correlations between severity of developing strain, overstrain and natural biorhythms course, and work intensity degree. The authors justified prophylactic measures to optimize work and rest schedule, to correct functional state, and other procedures to prevent stress and overstrain.

[Research on the method of stress assessment--from the research findings of 2010]

The Japanese Society for Occupational Mental Health has conducted research on assessment of the psychological load (i.e., stress) among workers. Investigations were conducted three times, and those were contract research projects assigned by the Ministry of Health, Labour and Welfare. In this project, the author was the primary researcher. In the latest research, a survey utilizing the Live Event Method was performed extensively nationwide; the survey covered 10,494 subjects (including 1,977 females) from all types of industry and occupation. The objective of this research was to reevaluate the Psychological Load Assessment Sheet used as an evaluation basis for the "Certification of workers' compensation related to mental disorders from psychological load." Two previous research investigations, conducted in 2002 and 2006, had suggested the need for such reevaluation. The outcomes revealed that, the longer the monthly overtime working hours, the higher the stress scores (in the range of 0 to 10), and the lower the appearance rate of stress. Subjects who performed 140 hours or more of overtime work per month, which fell under the category of "Extremely Excessive Overtime Work," showed 6.3 points, which was markedly high, and ranked fourth in the survey with 63 assessment items. The category, "Extremely Excessive Overtime Work," includes two working hour ranges, 120 hours or more and 160 hours or more; those working hour ranges were defined in the revision based on the latest research. Monthly overtime work of 120 hours or more, but less than 140 hours, was ranked ninth and scored 6.3 points. Monthly overtime work of 80 hours or more, but less than 100 hours, scored 5.3 points with a frequency of 14.2%. Based on the above results, new assessment items were added to the Psychological Load Assessment Sheet. This paper addresses and studies the issues explained above.