Sleep hygiene practices and sleep duration in rotating-shift shiftworkers

Abstract

Alcohol, caffeine and tobacco intake, exercise, activities on going to bed, and sleep-enhancing measures were assessed in 72 rotating-shift shiftworkers to determine whether these variables differ following day shifts and night-shifts, and which are related to sleep duration. Only alcohol intake and exercise prior to sleep, and feeling drowsy when retiring, differed following the night-shift. Workers generally followed recommendations concerning alcohol intake, sleeping immediately on retiring, and exercising, but acted contrary to recommendations concerning caffeine and nicotine intake. The only behaviour clearly associated with poor sleep was smoking, which reduced sleep duration.     

Effects of age and domestic commitment on the sleep and alertness of female shiftworkers

Abstract

In this study, the combined effects of age and domestic commitment on sleep duration, sleep difficulties and alertness in a sample of female shiftworkers were studied. A total of 572 nurses working in general hospitals in England completed a questionnaire. Two main shift systems were worked by the nurses: permanent nights or rotating shifts. Initial analysis revealed significant differences between these two groups of nurses, resulting in separate analysis of each group. Regression analysis showed that although older nurses had shorter sleep duration they did not report more sleep difficulties, in addition, their overall on-shift alertness was higher compared to younger nurses. Domestic commitment, defined as the number of dependants in the household and the level of perceived work-home conflict, not only reduced sleep duration, but also resulted in more sleep difficulties and lower on-shift alertness for most of the shifts. Two implications with regards to the relationship between age and sleep are discussed. First, the study points to the relevance of considering both biological and social factors when looking at age and sleep. Secondly, the study shows that the effects of age on sleep duration and sleep difficulties are not similar. This finding requires further research, especially in the light of the higher levels of alertness reported by older nurses.     

Is there an optimum number of night shifts? Relationship between sleep, health and well-being

By concentrating on the impact of a specific shift-system feature on the well-being of those concerned, rather than on the impact of the shift system as a whole, one might be able to offer more meaningful suggestions as to what constitutes a better form of shift system. The present study focused on the impact of the number of consecutive night shifts worked on the health and well-being of two groups of nurses (permanent night and rotating shift). All nurses completed a copy of the Standard Shiftwork Index, which is a set of questionnaires designed for comparing the effects of different types of shift system on large groups of workers. It includes measurements of psychological ill-health, physical ill-health, chronic fatigue, social and domestic disruption, attitudes towards shiftwork, sleep quality and sleep habits. Results showed clearly the impact of the number of consecutive nights worked on health and well-being, not directly, but indirectly through the impact on sleep duration and sleep quality. Sleep duration was shown to increase with more consecutive nights worked. This in turn was found to predict sleep quality, which in turn was found to be the stronger direct predictor of psychological and physical ill-health: i.e. better health was associated with longer and better quality sleeps. Explanations in terms of circadian adaptation are discussed.     

Sleep and napping in young shiftworkers: A 5-year follow-up

Abstract

The present study examined sleep characteristics in young workers who entered rapidly rotating shiftwork for the first time and stayed on shifts for 5 years. Data were collected when the subjects had shiftwork experience of approximately 1.5, 3.5 and 5.5 years and a mean age of 22, 24 and 26 years. Data are presented showing significant differences in the main sleep durations between situations within the shift cycle and a small reduction in overall sleep over the observed period, primarily due to a sleep reduction on afternoon shift days. Data on sleep quality did not show any change over this early period of shiftwork exposure. In addition, napping strategies did not change, with the exception of a small increase in those taking naps on night-shift days between 1.5 years and 3.5 years of shiftwork exposure. At all the observed phases there were more young shiftworkers taking a nap on the morning shift days than on the night-shift days. The data suggested that reduced sleeps on morning and night-shift days were not compensated by taking a nap, but rather with an increase in main sleep duration on afternoon shift days and days off. A weak tendency for individuals to be relatively long or short sleepers irrespective of sleep conditions could be seen.     

Is there an optimum number of night shifts? Relationship between sleep,health and well-being

Abstract

By concentrating on the impact of a specific shift-system feature on the well-being of those concerned, rather than on the impact of the shift system as a whole, one might be able to offer more meaningful suggestions as to what constitutes a better form of shift system. The present study focused on the impact of the number of consecutive night shifts worked on the health and well-being of two groups of nurses (permanent night and rotating shift). All nurses completed a copy of the Standard Shiftwork Index, which is a set of questionnaires designed for comparing the effects of different types of shift system on large groups of workers. It includes measurements of psychological ill-health, physical ill-health, chronic fatigue, social and domestic disruption, attitudes towards shiftwork, sleep quality and sleep habits. Results showed clearly the impact of the number of consecutive nights worked on health and well-being, not directly, but indirectly through the impact on sleep duration and sleep quality. Sleep duration was shown to increase with more consecutive nights worked. This in turn was found to predict sleep quality, which in turn was found to be the stronger direct predictor of psychological and physical ill-health: i.e. better health was associated with longer and better quality sleeps. Explanations in terms of circadian adaptation are discussed.     

Effects of sleep inertia on cognitive performance following a 1-hour nap

Abstract

This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, when compared with no-nap, reflecting SI effects. In SM, the slowing lasted 24 min, and 27 min in LR. Practical implications of the results are discussed.     

Effects of sleep inertia on cognitive performance following a 1-hour nap

This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, when compared with no-nap, reflecting SI effects. In SM, the slowing lasted 24 min, and 27 min in LR. Practical implications of the results are discussed.     

Interactive effect of individual factors on nurses' health and sleep

There is a tendency in studies concerning individual diferences in shiftwork tolerance to analyse the moderating effect of individual factors separately as if they acted independently. The aim of this study was to examine the interactive effect of individual factors (i.e. morningness, flexibility, languidity, neuroticism, extroversion) on nurses' health and sleep. A hundred female nurses (mean age 25.9 years, SD = 3.7 years) working a 2 × 12-h shift system were chosen from a larger study conducted among Intensive Care Unit staff. All subjects completed the Standard Shiftwork Index. Multiple regression analyses show that interactions of neuroticism and other factors (languidity, morningness) predict the majority of health and sleep complaints rather than neuroticism itself. Correlation analyses revealed that the interaction of neuroticism and languidity correlates higher with some indices of impaired health and sleep disturbances than when these factors are taken separately. The contribution of flexibility together with extroversion in interactions with neuroticism, and with neuroticism and languidity weaken the relations of languidity and neuroticism with health and sleep indices. The results show that some individual features tend to strengthen or counteract one another in relation to symptoms of shiftwork intolerance.     

Interactive effect of individual factors on nurses' health and sleep

Abstract

There is a tendency in studies concerning individual diferences in shiftwork tolerance to analyse the moderating effect of individual factors separately as if they acted independently. The aim of this study was to examine the interactive effect of individual factors (i.e. morningness, flexibility, languidity, neuroticism, extroversion) on nurses' health and sleep. A hundred female nurses (mean age 25.9 years, SD = 3.7 years) working a 2 × 12-h shift system were chosen from a larger study conducted among Intensive Care Unit staff. All subjects completed the Standard Shiftwork Index. Multiple regression analyses show that interactions of neuroticism and other factors (languidity, morningness) predict the majority of health and sleep complaints rather than neuroticism itself. Correlation analyses revealed that the interaction of neuroticism and languidity correlates higher with some indices of impaired health and sleep disturbances than when these factors are taken separately. The contribution of flexibility together with extroversion in interactions with neuroticism, and with neuroticism and languidity weaken the relations of languidity and neuroticism with health and sleep indices. The results show that some individual features tend to strengthen or counteract one another in relation to symptoms of shiftwork intolerance.     

Your work may be killing you! Workaholism,sleep problems and cardiovascular risk

This study tests the relationships between workaholism (i.e. working excessively and compulsively), sleep problems and cardiovascular risk in 537 employees from five Spanish hospitals. Four types of worker (i.e. workaholics, positive workers, compulsive workers and hard workers) were distinguished, and their health indicators were compared. The results showed that workaholics experienced significantly more sleep problems (i.e. morning tiredness, sleeping while driving and sleeping fewer hours both on weekdays and at weekends, with poorer quality), had higher relative risk scores, and consumed more caffeine and alcohol than the other patterns of worker (positive, compulsive and hard workers). Further analyses revealed that sleep problems fully mediated the relationship between workaholism (i.e. working excessively and compulsively) and cardiovascular risk. The study emphasizes the fact that being a workaholic might be a significant risk factor for having sleep problems and cardiovascular disease.     

The recovery paradox: Portraying the complex interplay between job stressors,lack of recovery,and poor well-being

Job stressors such as time pressure, organizational constraints, and interpersonal conflicts matter for individual well-being within organizations, both at the day level and over longer periods of time. Recovery-enhancing processes such as psychological detachment from work during nonwork time, physical exercise, and sleep have the potential to protect well-being. Although the experience of job stressors calls for effective recovery processes, empirical research shows that recovery processes actually are impaired when job stressors are high (recovery paradox). This article presents explanations for the recovery paradox, discusses moderating factors, and suggests avenues for future research.     

Effort-reward imbalance,overcommitment and sleep in a working population

The relationship between workplace characteristics and nocturnal sleep in a working population was investigated. Data from 709 employees (mean age=39 years; 87% men) from two German companies were analysed at the entry of the longitudinal cohort study (overall accrual 73%). We investigated the association between the effort-reward imbalance model at work (Siegrist, ) and self-reported sleep quality and sleep disturbances, as assessed by the Jenkins Sleep Quality Index. Effort and overcommitment were found to be higher, and reward was lower in participants with lower (N=328) vs. higher sleep quality (N=381), as well as in participants with (N=217) vs. without (N=492) disturbed sleep (all ps<.001). In regression analyses, lower sleep quality (R ²=.33) and sleep disturbances (R ² _Nagelkerke=.33) were predicted by older age, female gender (only significant for sleep disturbances), shift-work, lower physical and mental health functioning, and higher overcommitment. Individuals were 1.7 times more likely to report disturbed sleep per standard deviation increase in overcommitment. Gender-stratified analyses revealed that higher overcommitment was associated with unfavourable sleep in men, while in women poor sleep was related to lower reward. The findings suggest that overcommitment at work interferes with restful sleep in men, while in women disturbed sleep may be associated with the amount of overcommitment and perceived job reward and sleep quality associated with the perceived reward.     

The many meanings of sleep

Reductions in sleep are concomitant with night shift work. Data are presented showing that these robust differences in sleep are even present in experienced permanent night shift workers who most prefer to work nights. A model is presented which relates these reductions to chronic sleep deprivation. This, in turn, may be associated with performance decrements, and lead to accidents and illness. Better work schedule selection, worker training programs, and preventive medical action are unproven but promising approaches to overturning this model.     

Nutrient intake in day workers and shift workers

The 24-h dietary intake, nutritional status parameters and psychosomatic factors of two-shift, three-shift and day workers were compared. Estimations of the dietary intake (across a work cycle) were made by use of a nutrient database. No significant differences were found between the groups for a large number of nutritional variables: intake of energy; intake and percentage of energy from protein, fat, total carbohydrates and sucrose; intake of coffee; and intake and density of vitamins and minerals. Only minor differences were found between the groups with regard to the quantitative intake of alcohol and calcium, and with regard to the quality of the diet (percentage of energy from alcohol, density of calcium). The groups differed significantly with respect to attitude towards work hours (three-shift workers being most negative in their attitude) and sleep disturbances (shift workers being most negative). The three-shift workers were more evening-oriented and they had higher concentrations of glucose in their blood. It was concluded that work hours not related to nutritional intake—at least not when total amounts across time are considered. It was also concluded that work hours were not related to Body Mass Index or blood lipids: triglycerides, total cholesterol, LDL (low-density lipoprotein) cholesterol and HDL (high-density lipoprotein) cholesterol.     

Nutrient intake in day workers and shift workers

Abstract

The 24-h dietary intake, nutritional status parameters and psychosomatic factors of two-shift, three-shift and day workers were compared. Estimations of the dietary intake (across a work cycle) were made by use of a nutrient database. No significant differences were found between the groups for a large number of nutritional variables: intake of energy; intake and percentage of energy from protein, fat, total carbohydrates and sucrose; intake of coffee; and intake and density of vitamins and minerals. Only minor differences were found between the groups with regard to the quantitative intake of alcohol and calcium, and with regard to the quality of the diet (percentage of energy from alcohol, density of calcium). The groups differed significantly with respect to attitude towards work hours (three-shift workers being most negative in their attitude) and sleep disturbances (shift workers being most negative). The three-shift workers were more evening-oriented and they had higher concentrations of glucose in their blood. It was concluded that work hours not related to nutritional intake—at least not when total amounts across time are considered. It was also concluded that work hours were not related to Body Mass Index or blood lipids: triglycerides, total cholesterol, LDL (low-density lipoprotein) cholesterol and HDL (high-density lipoprotein) cholesterol.     

Sustained work, fatigue, sleep loss and performance: A review of the issues

The physiological and psychological stressors associated with sustained work, fatigue, and sleep loss affect worker performance. This review describes findings relating to sustained work stresses commonly found in our advancing technological world. Researchers report decrements in sustained performance as a function of fatigue, especially during and following one or more nights of complete sleep loss, or longer periods of reduced or fragmented sleep. Sleep loss appears to result in reduced reaction time, decreased vigilance, perceptual and cognitive distortions, and changes in affect. Sleep loss and workload interact with circadian rhythms in producing their effects. These interactions are a major source of stress in work situations requiring sustained work in continuous operations and have implications for theoretical models of sustained perceptual and cognitive functioning.     

Do eating and drinking habits interact with work schedule variables?

When compared to day workers, night-shift workers report that they eat fewer meals, have poorer appetites, are less satisfied with their eating habits, and eat at different times of the day. When demographic variables are held constant, there do not appear to be any significant differences between experienced day and night-shift workers in caffeine or alcohol consumption. Exceptions to and variations in these findings are probably due to the background influences of social and cultural variables. Eating and drinking behaviours do effect human performance and mood, but little relevant data have been gathered from experienced night-shift workers. There are no shiftworker data evaluating the effectiveness of the special diets or dietary recommendations that have been proposed for use by night-shift workers. Thus, attempts to manipulate night-shift worker eating and drinking habits require experimental test.     

Ten-hour days and eight-hour nights: Can the Ottawa Shift System reduce the problems of shiftwork?

Most research on condensed working weeks has concentrated either on daywork only or on 12-h shifts. The Police Force in Ottawa, Canada, have been reporting positive experiences with a shift system which retains an 8-h night shift but which extends the day shifts to 10-h, thus enabling a 6-day rest period following night shifts. In the present study, the effects on well-being, personal, social and work disruption, alertness and sleep were evaluated when the same system was adopted by a police force in the UK. A survey was conducted at four police stations prior to the change and again 6 months after the change. Two of the stations did not change to the Ottawa system and hence formed a control group. The stations originally worked 8-h shifts with blocks of seven consecutive shifts. The results suggest that, in contrast to the control group the 'Ottawa' group experienced a significant improvement in well-being, a significant reduction in personal, social and work disruption, and a significant increase in average sleep duration over a shift cycle. Self-rated alertness at the end of shifts was no worse under the Ottawa system. However, the values were still very low at the end of the night shift and, with an average sleep duration between night shifts of only 6-4-h it suggests that the block of seven nights in the Ottawa system may need review.     

Auditory evoked potentials as a function of sleep deprivation

Event-related brain potentials (ERPs) were studied in subjects deprived of sleep over a 48-h test period to assess the effects of different durations of continuous wakefulness on ERP components and to determine whether changes in the ERP components were related to changes in performance. Forty subjects were randomly assigned to either an experimental (sleep deprived) group (n = 30) or a control (not sleep deprived) group (n = 10). For the experimental subjects, ERP and performance measures were obtained in four-h test blocks throughout the 48-h period. Performance was assessed using the Walter Reed performance assessment battery. The control subjects were tested at the same times except during designated sleep periods. Both performance and evoked potential measures showed systematic changes over the experimental test period in association with sleep deprivation, time of day, and repeated testing. The latency of the N2 component of the evoked potential covaried with throughput measures on the performance assessment battery across the 12 four-h test blocks of the experiment. These data suggest that ERPs reflect central processes that change across the sleep deprivation period and that ERP measures might be useful in assessment and prediction of performance degradation under adverse conditions such as sleep loss.     

The after-effects of a prolonged period of day-sleep on subjective sleep quality

The effects of day-sleep on the quality ofsleep are not restricted to the night-work period itself. Effects can be measured during night-sleep in the period following night-work. A study on these after-effects, using a self-report instrument to measure sleep quality, is described. A total of N=7O operators wcrc observed over five consecutive undisturbed nights after a working period of seven morning shifts (N= 35) and after a working period of seven night-shifts (N= 35). The quality of sleep during the third night after the night-shift period was still significantly worse than the third night after the rnorning-shift period. No differential (after-)effects were observed with respect to differences in sleep duration.