Sleep Complaints and Polysomnographic Findings: A Study of Nuclear Power Plant Shift Workers

The literature widely recognizes that shift workers have more health complaints than the general population. The objective of this study was to describe the prevalence of sleep complaints and verify the polysomnographic (PSG) variables of shift workers in two Brazilian nuclear power plants. We carried out a subjective evaluation with a sleep questionnaire. Based on these results, the interviewees that reported sleep‐related complaints were referred for polysomnographic evaluation. Of the 327 volunteers initially evaluated by the sleep questionnaire, 113 (35%) reported sleep complaints; they were significantly older, had higher body mass index (BMI), and worked more years on shifts than those without sleep complaints. Of these 113, 90 met criteria for various sleep disorders: 30 (9%) showed obstructive sleep apnea (OSA), 18 (5.5%) showed limb movement, and 42 (13%) evidenced both sleep problems and had a significantly higher proportion of sleep stage 1 and arousals compared with the 23 shift workers that had no indices of sleep problems. The present study found that 90 (27.5%) of the evaluated participants met the PSG criteria of some type of clinical sleep disorder. This high proportion should be investigated for associations with other aspects of work, such as working hours, working schedule, years performing shift work, and access to health services. Due to the strong association between sleep disorders and the incidence of fatigue and sleepiness, the evaluation of the sleep patterns and complaints of shift workers is essential and should be considered to be one of the basic strategies of industry to prevent accidents.     

Sleep Disturbances Among Female Nurses: Comparing Shift to Day Work

Recently, attention has focused in Israel on the possible legal and health consequences of shift work. We decided to study sleep disorders among female nursing personnel working a shift schedule, in comparison with day nurses, in a large metropolitan general hospital. The study population was composed of 131 female certified nurses working shifts and 44 working days only. Inclusion criteria for the survey was at least 1 year of shift work alternating between day, evening, and night shifts, or at least 1 year of day work. All participants completed a self-report sleep questionnaire encompassing (a) demographic data, (b) sleep survey, and (c) employment details. Statistical analysis was performed using the Pearson correlation test and analysis of variance multiple range test (according to Scheffe's procedure). No significant correlation was found between sleep disorders and age of subjects. No sleep disorders were reported by 19.8% of shift workers versus 76.5% of day workers. Statistically significant findings were that the number of shifts per week >4.1 (p = 0.001) and duration of shift work >13.6 years (p = 0.007) correlated with the presence of sleep disorders. An additional significant finding (p = 0.014) was the impact of evening shifts on sleep disorders. The present small study confined to women supports the growing body of data on sleep complaints among shift workers.     

Disturbed sleep in shift workers, day workers, and insomniacs

Very little is known about differences in sleep between day and shift workers in representative samples of the population. This study compared a national representative sample (N=3400) of shift (with night shifts) and day workers regarding the different types of sleep disturbances and also the level of sleep symptoms with that of insomnia patients. The results showed very few differences between shift and day workers; only "too little sleep" and "nodding off at work" were marginally higher among shift workers. The results also showed that the complaints of insomnia patients for most sleep disturbances corresponded to the 2nd-16th percentile of the shift workers' levels of complaints. The results suggest, at least with the present questionnaire methodology, that shift work does not appear to be a major source of sleep disturbances and that their complaint levels bear no resemblance to those seen in insomniac patients.     

Disturbed Sleep in Shift Workers,Day Workers,and Insomniacs

Very little is known about differences in sleep between day and shift workers in representative samples of the population. This study compared a national representative sample (N=3400) of shift (with night shifts) and day workers regarding the different types of sleep disturbances and also the level of sleep symptoms with that of insomnia patients. The results showed very few differences between shift and day workers; only “too little sleep” and “nodding off at work” were marginally higher among shift workers. The results also showed that the complaints of insomnia patients for most sleep disturbances corresponded to the 2nd–16th percentile of the shift workers' levels of complaints. The results suggest, at least with the present questionnaire methodology, that shift work does not appear to be a major source of sleep disturbances and that their complaint levels bear no resemblance to those seen in insomniac patients.     

Comparison of Two Different Actigraphs with Polysomnography in Healthy Young Subjects

The present study aimed to compare two commercially available actigraphs, with a concurrent polysomnographic (PSG) recording. Twelve healthy volunteers (six women; age range 19–28 yrs) simultaneously wore the Basic Mini‐Motionlogger® and Actiwatch® for seven overnight polysomnographic recordings. Comparisons of the following sleep measures were focused on: sleep onset latency (SOL), total sleep time, wake after sleep onset, and sleep efficiency. Both devices underestimated SOL in comparison to PSG, but they had similar performance compared to PSG for the other sleep measures. A limit of the study is that the results can be only generalized to healthy young subjects.     

Comparison of two different actigraphs with polysomnography in healthy young subjects

The present study aimed to compare two commercially available actigraphs, with a concurrent polysomnographic (PSG) recording. Twelve healthy volunteers (six women; age range 19-28 yrs) simultaneously wore the Basic Mini-Motionlogger^® and Actiwatch^® for seven overnight polysomnographic recordings. Comparisons of the following sleep measures were focused on: sleep onset latency (SOL), total sleep time, wake after sleep onset, and sleep efficiency. Both devices underestimated SOL in comparison to PSG, but they had similar performance compared to PSG for the other sleep measures. A limit of the study is that the results can be only generalized to healthy young subjects.     

Can we consider medical residents as shift workers?

Although medical residents are characterized by long working hours, night shifts and high levels of work load, it is unclear if their work schedule can be classified as shift work, or if it has a similar impact on residents' well-being. The present paper compared the profile of complaints about sleep or daytime functioning of medical residents to that of rotating shift workers and day workers, of similar ages. Sixty-one residents (aged: 32.2 +/- 2.2 years), after 2 years of residency, participated in the study. The two control groups with a similar age range (26-40 years) were chosen, and included 94 rotating shift workers and 146 day workers. All subjects completed self-administered questionnaires on their sleep habits, and their sleep-wake cycle was monitored by a wrist-worn actigraph. Ten percent of the residents complained about difficulties falling asleep, 34% complained about morning tiredness, 14% complained about mid-sleep awakening, and 20% about prolonged fatigue. The residents slept significantly less than the day workers, and their sleep efficiency was significantly higher. When examining their subjective complaints profile, residents complained more than day workers and their answers were more similar to those of rotating shift workers, therefore they can be considered to be characterized as shift workers.     

Relationship between shift work schedule and self-reported sleep quality in Chinese employees

Few studies have reported on the effects of fixed and rotating shift systems on the prevalence of sleep disturbance. Thus, in this study, the relationships between different work schedules and sleep disturbance in Chinese workers were investigated. A total of 2180 workers aged 19–65 years responded to the self-report questionnaire on shift work schedule (fixed day-shift, fixed night-shift, two-shift or three-shift system), working hours a day, and working days a week, physical effort, subjective sleep quality and subjective mental state. It was found that the rotating shift workers, namely, two- and three-shift workers, exhibited higher risks of sleep disturbance than with the fixed day-shift workers did (OR 1.37; 95% CI 1.07to 1.74; and OR 2.19; 95% CI 1.52 to 3.15, respectively). The risk was particularly high among two- or three-shift workers who worked more than 8 hours a day or more than 5 days a week and among three-shift workers who reported both light and heavy physical effort at work. Moreover, the two- and three-shift workers (rotating shift workers) suffered from poorer sleep quality than the fixed night shift workers did (OR 1.84; 95% CI 1.01 to 3.32; and OR 2.94; 95% CI 1.53 to 5.64, respectively). Consequently, rotating shift work (two- and three-shift work) is a risk factor for sleep disturbance, and the fixed work rhythm may contribute to the quality of sleep.     

Elevated Plasma Homocysteine in Older Shift‐Workers: A Potential Risk Factor for Cardiovascular Morbidity

There is evidence supporting an association between shift work and cardiovascular morbidity, but the underlying mechanisms are unknown. The present paper investigated the levels of cardiovascular biochemical risk factors in shift‐workers both with (n=26) and without (n=103) sleep complaints, and in day‐workers (n=173) working in the same plant. Blood samples were taken in the morning after an overnight fast and analyzed for homocysteine, C‐reactive protein, and lipid profile. Biochemical data were compared among groups after stratifying workers by age (i.e., <40 and ≥40 yrs). Shift‐workers who complained about sleep disturbances and who were ≥40 years of age had significantly higher levels of homocysteine than did their younger counterparts—shift‐workers who did not complain of sleep disturbances and day‐workers. There were no other between‐group differences in any of the biochemical variables. The results of this investigation demonstrate an association between sleep disturbances in older shift‐workers and mild hyperhomocysteinemia. The elevated homocysteine levels may play a role in the increased rates of cardiovascular morbidity in shift‐workers, and they may have practical implications regarding the nutrition of shift‐workers.     

Sleep parameters among offshore workers: an initial assessment in the Campos Basin, Rio De Janeiro, Brazil

Shift work has potentially adverse effects on health, particularly on sleep. The purpose of the present study was to assess sleep parameters among personnel working in oil and gas offshore installations in the Campos Basin, Rio de Janeiro, Brazil. One hundred and seventy-nine subjects were asked to complete a sleep questionnaire with multiple-choice answers. Offshore workers were divided into two groups according to their work schedule: (1) fixed daytime workers (n = 86; age: 35.8+/-9.6 yrs) and (2) shift (n = 87) or night (n = 6) workers (total n = 93; age: 37.7+/-9.7 yrs). Shift/night workers reported poor sleep more frequently than the daytime workers (20.4% vs. 1.2%, p < 0.01), as well as habitual difficulty in falling asleep (15.1% vs. 4.7%, p<0.01), long latency of sleep onset (28% vs. 7%, p<0.01), fragmented sleep (45.2% vs. 16.3%, p<0.01), short sleep episodes (44.1% vs. 16.3%, p < 0.01), irregular bedtimes (29.0% vs. 12.8%, p < 0.01), and feeling tired upon awakening (15.1% vs. 3.5%, p < 0.01). Habitual napping and loud snoring were reported twice as often in shift/night than in day workers (p < 0.01). Nightmares, somnambulism, and unpleasant feeling in the legs were equality reported by both groups (p > 0.05). Few offshore workers had sought medical help for their sleep problems. A higher number of shift/night workers reported feelings of sadness compared with day workers (26.9% vs. 9.3%, p < 0.01). The findings of this study show that subjective reports of sleep-related problems are quite common among Brazilian offshore shift workers. Reliance on self-reported sleep problems and a cross-sectional design are the main limitations of our study.     

Diseases in Patients Coming to a Sleep Center with Symptoms Related to Restless Legs Syndrome

Study Objective

To explore the profile of patients who visit a sleep center with symptoms that fulfill the four essential criteria for restless legs syndrome (RLS).

Design

A prospective study.

Setting

Outpatients from one sleep disorders clinic in Taiwan.

Participants

1,200 consecutive patients visit sleep disorders clinic with any sleep complaints.

Interventions

After completing a history and physical examination, all participants answered the RLS questionnaire. Subjects who fulfilled the four essential criteria for RLS were referred to a special clinic. A work-up including blood tests, polysomnography, and specialized neurological tests etc. was performed to make the final diagnosis.

Measurements and Results

A total of 1,185 participants were enrolled, and, of these, 131(11.1%) fulfilled the four essential criteria for RLS, and 121 completed the supplemental work-up. Their mean age was 47.6±13.3 and 52.9% were male. Insomnia and snoring were the most common chief complaints. Obstructive sleep apnea syndrome and other diseases were found in 103 patients. Only 18 (14.9%) patients had no comorbid condition and were diagnosed with primary RLS.

Conclusions

Symptoms of RLS are common in patients with sleep complaints. Even in a sleep clinic, using a questionnaire approach for identification of RLS has a low positive predictive value. Clinicians should pay attention to the limitations of the 4-item questionnaire in diagnosis of RLS and also the importance of a careful differential diagnosis to identify possible secondary causes of RLS.     

The Amount of Diurnal Sleep, and Complaints of Fatigue and Poor Sleep, in Night-Working Women: The Effects of Having Children

This study deals with female industrial night workers. There is little scientific literature on this topic since, until recently, such shift systems have in most countries been restricted to men. The amount of diurnal sleep, as well as complaints about fatigue and poor sleep, were compared in women who were (n = 17) or were not (n = 26) caring for children. The women were engaged at an assembly line, working nights (22:00-06:00) from Monday to Friday. They filled out sleep logs for 10 consecutive weeks and were interviewed about complaints concerned with fatigue and poor sleep. A comparison of the diurnal sleeps taken between consecutive night shifts showed that the average total length of daily sleep, as well as the time of onset of the first sleep, did not differ between the groups; however, workers who had children tended to show, in comparison with their childless colleagues, more sleep episodes per day and a shorter first sleep. The total number of complaints about poor sleep and fatigue did not differ between the groups; nevertheless, workers with children complained more of difficulty in falling asleep, had a greater dissatisfaction with the amount of sleep on weekdays, and tended to show an increasing fatigue as the week progressed. We conclude that there are social pressures in women who care for children that are in addition to those that are a general consequence of night work. These results reinforce a need for the implementation of measures that organise child care, so helping a mother who wishes to work also outside the home.     

Shift work tolerance and the importance of sleep quality: a study of police officers

The aim of this study was to examine how subjective shift work tolerance was related to general health variables, with the expectation of inter-individual differences in the nature of this relation. A total of 740 employees of the Dutch Police force completed a questionnaire, covering seven health-related domains: sleep quality, sleep duration, need for recovery, fatigue, physical health, mental health, and work–life balance. Based on subjective reports of shift work tolerance, participants were classified as intolerant, medium-tolerant, or tolerant workers. Analysis involved group comparisons, regression, and cluster analysis. Eighteen percentage of the shift workers were classified as intolerant. The intolerant and medium-tolerant workers expressed more severe complaints than the tolerant workers, for all seven health-related domains. Shift work tolerance was primarily related to sleep quality and subsequently to need for recovery, fatigue, and work–life balance. No indications were found for systematic inter-individual differences in the nature of this relationship. For all participants equally, the degree of shift work tolerance was related to the severity of health-related complaints. This study highlights the central role of sleep for tolerance to shift work and underlines the need for occupational medicine to take explicit account of sleep.     

Self-Reported Health and Sleep Complaints Among Nursing Personnel Working Under 12 h Night and Day Shifts

This cross-sectional exploratory study involved health care workers of various skill types and levels. We tested the hypothesis that the prevalence of diseases, sleep complaints, and insufficient time for nonprofessional activities (family, leisure, and rest) are higher among night than day workers. Data collection was carried out in two public hospitals using questionnaires and other forms. Night work was explored as a risk factor, considering a night worker as one who had at least one night job on the occasion of the research. Data were assessed by a univariate analysis. The association between work schedule and the dependent variables—health conditions, sleep complaints, and insufficient time for nonprofessional activities—was evaluated through the estimation of the prevalence ratio, with a confidence interval of 95%. Two hundred and fifty-eight female nursing personnel participated; 41.5% were moonlighters, and only 20 worked a shift of less than 12 h in length. Reports of migraine and need of medical care the 2 weeks before the survey were more prevalent among day than night workers (PR = 0.71; CI = 0.55–0.92 and PR = 0.71; CI = 0.52–0.95, respectively). Migraine headaches occurred less frequently among night than day workers as confirmed by comparing the reports of the night workers and day workers whose work history was always day shifts (PR = 0.74; CI = 0.57–0.96). Reports of mild emotional disorders (mild depression, tension, anxiety, or insomnia) were less frequent among night (PR = 0.76; CI = 0.59–0.98) and ex-night workers (PR = 0.68; CI = 0.50–0.91) than day workers who never had worked a night job. The healthy worker effect does not seem to explain the results of the comparisons between day and night workers. The possible role of exposure by day workers to some risk factors, such as stress, was suggested as an explanation for these results. No significant difference was observed between night and day workers as to sleep complaints, a result that may have been influenced by the nature of the shift-work schedule (no successive night shifts) and possibly nap taking during the night shift. Moreover, the long work hours and moonlighting of the healthcare workers, which is common in Brazil, may have masked other possible differences between the day and night workers. Among night workers, a significant relation was found between years working nights (more than 10 yrs) and high cholesterol values (PR = 2.58; CI = 1.07–6.27), a result that deserves additional study. Working nights more than four times per 2-week span was related to complaints about insufficient time for children (PR = 1.96; CI = 1.38–2.78) and rest/leisure (PR = 1.54; CI = 1.20–1.99). These results can be related to the “social value of time,” as evenings and nights are when families usually spend time together. The complexity of the professional life and the consequent heterogeneity of the group of workers under shift-work schemes confound the results. More in-depth study of the questions raised here demands a more sophisticated epidemiological treatment and larger sample size.     

The Amount of Diurnal Sleep,and Complaints of Fatigue and Poor Sleep,in Night-Working Women: The Effects of Having Children

This study deals with female industrial night workers. There is little scientific literature on this topic since, until recently, such shift systems have in most countries been restricted to men. The amount of diurnal sleep, as well as complaints about fatigue and poor sleep, were compared in women who were (n = 17) or were not (n = 26) caring for children. The women were engaged at an assembly line, working nights (22:00-06:00) from Monday to Friday. They filled out sleep logs for 10 consecutive weeks and were interviewed about complaints concerned with fatigue and poor sleep. A comparison of the diurnal sleeps taken between consecutive night shifts showed that the average total length of daily sleep, as well as the time of onset of the first sleep, did not differ between the groups; however, workers who had children tended to show, in comparison with their childless colleagues, more sleep episodes per day and a shorter first sleep. The total number of complaints about poor sleep and fatigue did not differ between the groups; nevertheless, workers with children complained more of difficulty in falling asleep, had a greater dissatisfaction with the amount of sleep on weekdays, and tended to show an increasing fatigue as the week progressed. We conclude that there are social pressures in women who care for children that are in addition to those that are a general consequence of night work. These results reinforce a need for the implementation of measures that organise child care, so helping a mother who wishes to work also outside the home.     

Shift-specific associations between age,chronotype and sleep duration

The objective of this study was to examine the association of age with chronotype and sleep duration in day workers and rotating shift workers, including night shift work. Between October 2012 and February 2015, a cross-sectional study was conducted in a German chemical company. Using the “Munich ChronoType Questionnaire” (MCTQ), data about sleep onset and sleep offset during workdays and work-free days were retrieved and the chronotype was computed during regular voluntary occupational health check-ups. Associations between age and chronotype, as well as sleep duration, were assessed using linear regression analyses. Potential effect modification by the working time system was examined. Within the study period, 4,040 employees (82.3% and 17.7% were engaged in day work and rotating shift work, respectively) completed the questionnaire. Study participants were on average 41.8 years old (Min = 18.0, Max = 65.0, SD = 10.2) and predominantly male (75.4%). Mean chronotype and overall sleep duration was 03:22 (SD = 54 min) and 7.2 h (SD = 1.0 h) respectively. Older age was associated with earlier chronotype and reduced overall sleep duration in both day workers and rotating shift workers (p < 0.001 for all models). Compared to day workers, employees whom engaged in rotating shift work were later chronotypes and had overall a longer sleep duration. With older age, the difference between day and rotating shift workers regarding chronotype increased, while the difference regarding overall sleep duration decreased (p_interaction<0.005 for both models). This finding could indicate that both changes in circadian physiology and exposure to certain work schedules contribute to the age-related changes. Older rotating shift workers, with early chronotypes may have issues with night shifts, while day work and morning shifts may be best compatible to earlier chronotypes. Differences in sleep timing across age groups, might indicate that the same work hours will affect shift workers differently, dependent on their age, suggesting that more flexible and chronotype-adapted work hours could provide useful; especially for older employees. Sleep education in the form of courses and health campaigns could be a way to raise awareness of the importance of a healthy sleep pattern. This could be achieved by learning strategies to better adjust individual sleep patterns to work hours.     

Sleeping under the Ocean: Despite Total Isolation,Nuclear Submariners Maintain Their Sleep and Wake Patterns throughout Their Under Sea Mission

BackgroundTo assess the effects of isolation, inadequate exposure to light and specific shift work on the subjective and objective measurements of sleep and alertness of submariners.PurposeA strictly controlled randomized crossover study with the polysomnography recorded twice during the mission.MethodsSetting: Shift and night work with prolonged (70 days) social isolation from the real world (with no phone or Internet contact with families or friends during a routine mission aboard the “Téméraire” French Strategic Submarine with Ballistic Nuclear missiles (SSBN). Participants: 19 submariners working on a 24-hour shift for three days in a row schedule. Interventions: The participants attended two polysomnographic (PSG) recordings of night sleep on Day 21 (D21) and Day 51 (D51) of the 70-day patrol; urine cortisol levels were also taken after sleep, and subjective assessments of sleep, sleepiness, mood and anxiety on D21 and D51. The light and temperature on board were also recorded.ResultsPSG analyses showed that sleep did not significantly vary in length (total sleep time) or in quality between D21 and D51. The mariners reported the same subjective sleep, sleepiness, anxiety or mood (except for a slightly worse score for confusion on D51). Blood cortisol levels did not vary significantly.ConclusionsThese results show that humans living in an isolated environment for more than two months with this specific shift schedule do not suffer from any significant effects on sleep, sleepiness and confusion between D21 and D51, when they follow an organized regular shift pattern with controlled light and temperature.     

Sleep patterns and sleep disorders among female shift workers in a computer factory of Japan

Using a repeated questionnaire survey for female workers in a computer factory of Japan, consisting of 45 daytime workers and 84 weekly rotating shift workers (of whom 40 and 44 were respectively engaged in early-shift work and late-shift work during the survey week), the present study aimed to clarify the effects of shift work on their sleep patterns and sleep disorders. The time of retiring, time of rising, duration of sleep, and self-evaluated sleep quality based on four sleep-related problems were investigated for four days (Sunday-Monday, Tuesday-Wednesday, Thursday-Friday, and Saturday-Sunday) in a week. The intergroup comparison revealed that the earlier the rising time and the shorter the duration of sleep, the lower the sleep quality; the lowest sleep quality was observed in the early-shift workers.     

The effects of double-shifts (15.5 hours) on sleep, fatigue and health

The aim of the present study was to investigate how "double-shifts" (15.5 hours) affects sleep, fatigue and self-rated health. The study was carried out on male construction workers of which 80% were long-distance commuters. The schedule involved two work periods and each work period involved two double shifts in a row. The subjects filled in a sleep/wake diary at 8 times across a year and a questionnaire at 3 times. They also wore an actigraph during one shift cycle. The results showed that sleepiness, and to a certain extent, mental fatigue increased during double shifts and accumulated across days. The short rest time (8.5 hours) between days caused insufficient sleep and approximately 5.5 hours of sleep was obtained between double shifts. Questionnaire data showed that complaints of insufficient sleep, exhaustion on awakening and pain symptoms increased across the year. It was concluded that a shift system involving double shifts has a negative effect on fatigue, recovery and health-related well-being.     

Shift work and sleep disorder comorbidity tend to go hand in hand

Taking into consideration that shift work has a wide-ranging impact on circadian and sleep functioning, it seems likely that shift work increases the risk of a general sleep disturbance, spread out over a multitude of comorbid sleep disorders. The aim of the present study is to analyze and present the sleep disorder data of 250 shift workers and 971 permanent day workers, taken from a nationally representative sample. Additional data concerning duration, timing, and quality of sleep, daytime functioning and social/family variables were added to the analyses. The results showed that the shift workers experienced significantly more difficulties with the variability of their sleep times, reported more napping and considered themselves more as poor sleepers than the day workers. Most importantly, shift work, in comparison with day work, appeared associated with a significantly higher prevalence of the clinical, International Classification of Sleep Disorders’ defined symptoms of nearly all main sleep disorders (including shift work disorder). For shift workers, the prevalence of a general sleep disturbance was 39.0% (95%CI 33.2 – 45.2), significantly higher than for day workers (24.6%, 95%CI 22.0 – 27.4). Moreover, shift workers were characterized by high levels of sleep disorder comorbidity. In addition, exclusively for shift workers, the prevalence of disordered sleep systematically decreased across decades of life and was considerably higher for single versus partnered shift workers. This study adds to the insight into the interacting factors that determine shift work coping and may play a role in occupational health interventions aimed at reducing sleep problems and thus improving the resilience and tolerance of the shift worker.