Shiftworkers report worse sleep than day workers,even in retirement

The aim of this study was to explore how the level of shiftwork exposure during an individual's working life might be related to subjectively reported sleep quality and timing during retirement. Telephone interviews regarding past employment and sleep timing and quality (among other variables) were conducted using a pseudo‐random age‐targeted sampling process. Subjective sleep quality was assessed using a telephone version of the Pittsburgh Sleep Quality Index. Timing of reported habitual bedtimes and rise‐times were assessed using the Sleep Timing Questionnaire. Questions measuring morningness and subjective health were also given. Retired seniors (aged >65 years, n = 1113) were studied. Analysis was by analysis of variance, with shiftwork exposure in three bins [0 (n = 387), 1–15 (n = 371) and >15 years (n = 355)], gender (n = 634 male, 479 female) and former occupation [in two broad categories, ‘managerial’ (n = 437) versus ‘other’ (n = 676)] as factors. In retired shiftworkers, relative to retired day workers, past exposure to shiftwork was associated with higher (worse) PSQI scores by 1.0 units (1–15 years) and 0.6 units (>15 years) (main effect P = 0.005). There were also main effects of gender and former occupation (males and managerials reporting better sleep), but neither variable interacted with shiftwork exposure. The timing of current mean habitual bedtimes and rise‐times (and also the variance around them) were very similar for the three shiftwork exposure groups. The shiftwork exposure effect did not appear to be mediated by either morningness or current health. Prior exposure to shiftwork would appear to be related to currently reported sleep problems during retirement.     

Prevalence and correlates of self-reported sleep problems among Chinese adolescents

STUDY OBJECTIVES: This study examined the prevalence and correlates of sleep problems in Chinese adolescents. DESIGN AND SETTING: An epidemiological questionnaire survey was carried out in five high schools in Shandong Province of Mainland China. PARTICIPANTS: A total of 1365 adolescents between the ages of 12 and 18 years comprising 823 boys and 542 girls. MEASUREMENTS AND INTERVENTIONS: The participants completed a self-administered questionnaire regarding sleep duration, sleep problems, stressful life events, lifestyles, and personal and family characteristics. RESULTS: Mean sleep duration at night was 7.64 hours (SD = 0.86) and decreased with increasing age. Of the sample, 16.9% (95% CI = 13.2-20.5%) reported insomnia symptoms including difficulty initiating sleep (10.8%), difficulty maintaining sleep (6.3%), and early morning awakening (2.1%). Nightmares were reported more frequently by girls (chi2=20.09, p<0.001). Only 2.3% of the sample had ever taken hypnotic medication during the past month. Almost 22% of the subjects went to bed later than 12:00 PM at least once a week. Multiple logistic regression analysis showed that greater age, being at senior high school, doing no habitual physical exercise, poor physical health, self-selection of diet, longer distance from home to school, and life stress experienced during the past 12 months were significantly associated with an increased risk of insomnia. CONCLUSIONS: Self-reported sleep problems in Chinese adolescents are common and associated with multiple factors. These findings suggest the need for comprehensive programs to prevent sleep problems in adolescents.     

Rapid changes in overnight blood pressure after transitioning to early-morning shiftwork

Risk for adverse cardiovascular events increases when blood pressure does not decrease at night (“non-dipping,” <10% decrease from daytime blood pressure). Shiftwork alters relationships between behaviors and endogenous circadian rhythms (i.e., circadian disruption along with variable sleep timing), and chronic shiftwork increases cardiovascular disease risk. To determine whether transitioning into shiftwork changes the overnight blood pressure dipping pattern, we leveraged a natural experiment that occurs when newly-hired bus operators transition from a daytime training schedule into an early-morning shiftwork or daywork schedule. Twenty participants were studied in a 90-day protocol upon new employment and underwent cardio-metabolic health assessments, including ambulatory blood pressure monitoring, and weekly sleep-wake diaries. Measurements were repeated after ~30 and 90 days after transitioning to a day or an early-morning shiftwork schedule. Newly-hired shiftworkers displayed dramatic changes in overnight blood pressure, with 62% converting from a healthy dipping blood pressure to the nondipping pattern, resulting in 93% of shiftworkers displaying a nondipping phenotype at 90-days. In contrast, 50% of dayworkers had a nondipping profile at baseline and this decreased to 0% at 90-days, a significant difference from shiftworkers (p = .001). At 90-days, overnight blood pressure dipping was ~7% less in shiftworkers than dayworkers (–6.3% [95%CI –3.7 to –8.8%] vs –13.1% [–10.3 to –15.9%]: p < .01), with changes in dipping associated with changes in sleep timing variability (r² = .28, p = .03). The observed changes in overnight blood pressure dipping in newly-hired early-morning shiftworkers, which were associated with sleep timing variability, may be an early warning sign of increased cardiovascular risk among shiftworkers.     

Implementation of napping In industry and the problem of sleep inertia

SUMMARY  It seems reasonable to believe that in specific situations napping at the work place would be possible and used if authorized and encouraged. Very short naps could have very positive long-term effects on biological functions. Training someone to sleep for short periods appears feasible if there is a high motivation to do so. Sleep inertia can be considered as one of the main limiting factors in napping strategy. Sleep inertia depends on different factors such as sleep stage preceding the awakening, temporal placement of the nap, duration of nap and wakefulness preceding it, etc. The effects of sleep inertia might be different depending on the type of task, and a reactivation technique applied immediately after awakening may remove it. Despite the fact that its implementation in industry raises some practical issues, napping can be considered as a possible strategy to increase the vigilance level of night workers.     

Hypnotics and caffeine as countermeasures for shiftwork-related sleepiness and sleep disturbance

SUMMARY  Hypnotic medication reliably improves sleep during the day, in terms of increasing total sleep time (TST) and reducing awakenings and light sleep. Middle-aged individuals may benefit more than young adults. In addition, the time of day during which sleep is attempted may influence the efficacious dose of short-acting drugs. Available data suggest that improving sleep during the day may improve alertness/performance at night to a mild degree, but significant circadian-related sleepiness remains. Hypnotic medication may help minimize the cumulative effects of sleep loss associated with daytime sleep. Use for more than one week has not been adequately studied; however, as most night and rotating workers' schedules allow for night-time sleep for two or more nights per week, available evidence indicates that hypnotics can be used effectively on an intermittent basis, e.g. for the first 2–4 day-sleep periods of night shifts. Caffeine has been shown to increase alertness and improve psychomotor performance during usual night-shift hours when taken between 22.30 and 01.20 hours. Available data indicate that at approximate dosages of 250–400 mg, the beneficial effects persist until at least 05.30 hours. For most subjects, caffeine taken at the start of the night-shift does not interfere significantly with daytime sleep beginning at 09.00 hours. There is also some evidence that single doses of caffeine at the beginning of a night shift may be more alerting than divided doses. If caffeine is to be used therapeutically, avoidance of social use may be required to avoid tolerance to CNS stimulant effects. Despite the positive results of laboratory research examining hypnotics or caffeine as shiftwork countermeasures, field trials have not been conducted.     

Methylation alterations at imprinted genes detected among long‐term shiftworkers

Exposure to light at night through shiftwork has been linked to alterations in DNA methylation and increased risk of cancer development. Using an Illumina Infinium Methylation Assay, we analyzed methylation levels of 397 CpG sites in the promoter regions of 56 normally imprinted genes to investigate whether shiftwork is associated with alteration of methylation patterns. Methylation was significantly higher at 20 CpG sites and significantly lower at 30 CpG sites (P < 0.05) in 10 female long‐term shiftworkers as compared to 10 female age‐ and folate intake‐matched day workers. The strongest evidence for altered methylation patterns in shiftworkers was observed for DLX5, IGF2AS, and TP73 based on the magnitude of methylation change and consistency in the direction of change across multiple CpG sites, and consistent results were observed using quantitative DNA methylation analysis. We conclude that long‐term shiftwork may alter methylation patterns at imprinted genes, which may be an important mechanism by which shiftwork has carcinogenic potential and warrants further investigation. Environ. Mol. Mutagen., 2013. © 2012 Wiley Periodicals, Inc.     

Hormonal and pharmacological manipulation of the circadian clock: recent developments and future strategies

The mammalian circadian oscillator, located in the suprachiasmatic nuclei of the anterior hypothalamus, serves as the principal source of rhythmic temporal information for virtually all physiologic processes in the organism, including the alternating expression of sleep and wakefulness. Recent studies, in both animal models and human subjects, have demonstrated the important modulation of sleep and wakefulness mediated by the circadian clock. Independent of other factors, notably prior sleep-wake history, the circadian clock potentiates wakefulness (and alertness) at one phase of the diurnal cycle, while facilitating sleep and its attendant processes at the opposite phase. The adaptive advantage of synchronizing sleep-wake behaviors with the daily changes in the external environment is clear. But in a modern world where the constraints of environmental time are less and less important, the circadian clock still imposes rigid boundaries on the timing of sleep and alert wakefulness that are increasingly perceived as limitations on human performance. This conflict underlies the sleep "disorders" of jet lag and shiftwork sleep disruption, problems that are not really diseases at all, but instead reflect normal function of circadian timing in the context of extraordinary demands on sleep-wake scheduling. Whatever their proper classification, both jet lag and shiftwork insomnia represent important societal problems deserving of public health and medical attention. Barring a worldwide rejection of air-travel, jet lag will continue to afflict tens of thousands of people annually. The effects of jet lag on human performance, while typically transient, can nonetheless be significant, affecting commerce, government, and even the outcome of professional sports contests. More important, only a global regression to an agrarian economy will eliminate the problem of tens of millions of workers in this country who regularly attempt to work at night and sleep during the day. In contrast to jet lag, shiftwork produces chronic sleep disruption lasting for the duration of shiftwork exposure. For while individual differences in the ability to adjust to a nocturnal work schedule clearly exist, recent studies suggest that few if any night workers regularly experience restful and restorative day sleep equivalent to that considered normal at night. This chronic sleep limitation is associated with significant increases in a number of consequent problems including sleepiness-related accidents, social disruption, and psychiatric disturbances. In addition, chronic exposure to shiftwork has now been shown to be an independent risk factor for the development of both cardiovascular and gastrointestinal diseases. While these epidemiological studies have not identified the specific aspect of shiftwork that is associated with increased risk of these disorders, the chronic limitation and disruption is foremost among plausible factors. The most important aspect of human circadian physiology that limits adaptation to the extreme schedules inherent in shiftwork and jet travel is the primacy of light among entraining signals, or zeitgebers. Exposure to sunlight for night shiftworkers, or for jet travelers at their destination, results in maintenance (or resetting) of the clock to environmental time. This response can be prevented or overridden with extraordinary avoidance of sunlight or with provision of artificial light of sufficient duration and intensity to negate the sunlight signal, an approach shown to be effective in the treatment of shiftwork sleep disruption. Practical issues sharply limit the application of artificial lighting to all shiftwork settings, however, and the role for a pharmacological chronobiotic agent capable of accomplishing the same end is potentially very large (Copinschi et al., 1995; Jamieson et al., 1998). For example, the effects of zolpidem vs. placebo on sleep, daytime alertness, and fatigue in travelers who complain of jet lag was co     

Occupational asthma, eosinophil and skin prick tests and serum total IgE values of the workers in a plant manufacturing rose oil

This study was aimed to determine the rate of occupational asthma (OA) in workers at a rose extracting plant. Specific clinical tests of 52 workers, randomly chosen from four local rose extracting plants, were statistically compared with the test results of 30 local control subjects of similar age and sex as the plant workers, but who had never worked in such a plant. There were no significant differences in pulmonary function tests (FVC, FEV1, FEV1/FVC, PEFR) between the control and test groups. Significantly higher serum total IgE values (p < 0.0001) were observed for the test subjects (239.08+/-240 IU/ml) compared to the control subjects (81.33+/-61.45 IU/ml). There were also significant differences (p < 0.0001) in the number of eosinophils between the control and test groups, with corresponding mean values of 2.28+/-2.75% and 0.73+/-1.72%, respectively. A specifically prepared skin prick test using a rose allergen (Rosa domescena) was positive for 53.84% in the test subjects whereas only 5.33% positive test results were seen in the control group. We have demonstrated the involvement of Rosa domescena pollen in occupational allergy, through IgE-mediated hypersensitivity. It was concluded that the workers of a rose oil extracting plant are more susceptible to the rose pollens.     

Correlation between wrist activity monitor and electrophysiological measures of sleep in a simulated shiftwork environment for younger and older subjects.

Although several studies have examined the correlation between nocturnal PSG and activity measurement, validation studies of actigraphically measured sleep in shiftworking populations have not been reported. This study investigates the correlation between sleep recorded using EEG and actigraphic techniques during a simulated 12-hour shift rotation. Thirty-two subjects were allocated to groups according to age. Group (1) included sixteen subjects mean (+/- s.d.) age of 21.2 +/- 2.7 years, and Group (2) included sixteen subjects mean (+/- s.d.) age of 43.9 +/- 6.8 years. An adaptation night was followed by two 12-hour day shifts (7 am-7 pm), 24 hours off and then two 12-hour night shifts (7 pm-7 am). For the entire study subjects wore an activity monitor, and while in bed, sleep was recorded using polysomnography; both techniques were collected in 30-second epochs. A high epoch for epoch agreement between wrist activity monitoring and EEG measures of sleep was recorded for daytime and nighttime sleep periods (80-90%). There was a high correlation between EEG and actigraphically recorded sleep duration in young (0.98-0.77) and older (0.78-0.96) subjects for all sleep periods. Sleep efficiency correlations were extremely variable for both the young (0.72-0.15) and older (-0.18-0.58) subjects for daytime and nighttime sleep periods. Taken together these results suggest that wrist activity monitoring is a valid measure of sleep/wake activity and sleep duration, in a simulated shiftwork environment. However, some caution should be used for more specific measures, such as sleep efficiency particularly in older subjects.     

Sleep and adolescent suicidal behavior

STUDY OBJECTIVES: Suicide risk begins to increase during adolescence. Adolescents do not get enough sleep and are also at risk for many sleep disturbances. This study examined the association between sleep patterns and sleep problems and adolescent suicidal behavior. DESIGN AND SETTING: A questionnaire survey of adolescents attending school was conducted in one prefecture of Shandong Province, People's Republic of China. PARTICIPANTS: A total of 1,362 adolescents attending school (mean age 14.6 years, 60% males) participated in the survey. MEASUREMENTS: Respondents completed a self-administered questionnaire that asked about sleep patterns, sleep problems, suicidal behavior, depressive symptoms, and demographic characteristics of the family and adolescent. RESULTS: Overall, 19.3% of the sample reported having suicidal ideation, 10.5% having suicide attempts in the past 6 months, 16.9% having insomnia symptoms, 2.3% having taken hypnotic medication, and 48.9% having experience of nightmares in the past month. Mean night sleep duration was 7.6 hours (SD = 0.8). Logistic regression analyses showed that sleeping less than 8 hours at night (OR = 2.89, 95% confidence interval [CI] = 1.07-7.81) and frequent nightmares (OR = 2.43, 95% CI = 1.76-3.35) were significantly associated with increased risk for suicide attempts after adjustment for age, sex, father's occupation, and depressive symptoms and that nightmares (OR = 1.69, 95% CI = 1.20-2.38) were also significantly related to suicidal ideation. CONCLUSION: These findings demonstrate the association between short sleep duration and nightmares and suicidal behavior and highlight the potential role of sleep intervention in the prevention of adolescent suicide.     

A process model of shiftwork and health.

The authors developed and tested a process model of adaptation to shiftwork, which hypothesizes that various individual and situational variables influence the development of sleep and social and domestic disturbances. Both types of disturbances trigger various types of coping behavior, leading to several proximal outcomes. The end result is the development of chronic health problems in the form of digestive and cardiovascular symptoms. The model was tested with survey data collected from 2 samples of nurses (N = 1,532) in the United Kingdom and was cross-validated against a 3rd sample of industrial workers (N = 370). Results indicate support for the model across the 3 samples, although some sample-specific and subgroup effects were found. Results have direct implications for the development of shiftwork theory and interventions.     

Sleep duration, subjective sleep need, and sleep habits of 40- to 45-year-olds in the Hordaland Health Study

STUDY OBJECTIVE: To report the distribution of various sleep parameters in a population-based study. DESIGN: Population-based cross-sectional study with self-administered questionnaires. SETTING: Conducted as part of the Hordaland Health Study '97-'99 in collaboration with the Norwegian National Health Screening Service. PARTICIPANTS: 8860 subjects, aged 40 to 45 years, answered the sleep questionnaire part of the study. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Reports on habitual bedtimes, rise times, subjective sleep need, and various sleep characteristics were used in this study. Mean (+/- SD) nocturnal sleep duration during weekdays in men was 6 hours 52 minutes (+/- 55 minutes); in women 7 hours 11 minutes (+/- 57 minutes). Mean subjective sleep need was 7 hours 16 minutes (+/- 52 minutes) in men; 7 hours 45 minutes (+/- 52 minutes) in women. Sleep duration was shorter in shift workers and longer in married subjects and in those living in rural areas. Subjective sleep need was higher in subjects reporting poor subjective health and in subjects living in rural areas. In total, these variables accounted for only around 3% of the variance in sleep duration and sleep need. Ten percent of the men and 12.2% of the women reported frequent insomnia. CONCLUSIONS: The wide distribution of sleep duration and subjective sleep need indicate large interindividual variations in these parameters. There were pronounced sex differences in these variables and in most of the sleep characteristics studied. Shift work, urban-rural living, marital status, and education in men were sources of significant, but small, variations in sleep duration.     

Sleepiness and shiftwork: individual differences

SUMMARY  On-site studies of shiftwork show considerable differences in sleepiness between workers. Variation between individuals depends on different sleeping, coping and living habits of the workers, on possible sleep disorders, but also on more 'permanent' inter-individual factors that may influence sleepiness by changing either the circadian or homeostatic factors of sleep. The effects of circadian phase, age, sex, physical fitness, domestic and personality factors on shiftworkers' sleepiness and work-related accidents are reviewed. It is concluded that only a minor part of the variation in sleepiness between individuals can be explained. The present knowledge is not sufficient to carry out reliable 'selection' of individuals suitable for shiftwork. However, preventive advice and medical surveillance focusing on individual differences in sleepiness are recommended.     

Subjective sleep disturbance and its correlates in middle-aged Hong Kong Chinese women

OBJECTIVES: To examine the factors associated with subjective sleep disturbance in middle-aged Hong Kong Chinese women. METHODS: A total of 305 women aged 45-55 years were recruited at community-based women's clubs. Eligible subjects were of Chinese ethnicity and not taking oral contraceptives, hormone therapy or had received surgical removal of ovary. Standardized questionnaires, including sociodemographic, health and life-style variables, Pittsburgh Sleep Quality Index (PSQI), Greene Climacteric Scale (GCS) and Perceived Stress Scale were administered. RESULTS: About 18% of the sample complained of difficulty initiating sleep, difficulty maintaining sleep or early morning awakening at least three times per week in the past month. About 26% of the women were poor sleepers as defined by a global PSQI score >5. Sleep difficulty was one of the five most commonly reported climacteric symptoms. Cross-sectional analysis found that significantly more peri- and postmenopausal women had subjective sleep disturbance than premenopausal women. Multiple logistic regression analysis showed that women who had high levels of somatic complaints, psychological symptoms and perceived stress had a four to sixfold increased risk of reporting disturbed sleep. Menopausal status was not an independent predictor. CONCLUSIONS: Comparison of our findings with recent literatures suggested a lower prevalence of insomnia in Hong Kong Chinese middle-aged females than Caucasian women. Somatic complaints, psychological symptoms and perceived stress were independent risk factors for sleep disturbance. Clinicians should screen for sleep problems in middle-aged Chinese women with prominent somatic and psychological symptoms and perceived stress.     

EEG spectral power and cognitive performance during sleep inertia: the effect of normal sleep duration and partial sleep deprivation

Sleep inertia (SI) is a transient period occurring immediately after awakening, usually characterized by performance decrement. When sleep is sufficient, SI is moderate, and produces few or no deficit. When it is associated with prior sleep deprivation, SI shows dose-dependent negative effects on cognitive performance, especially when subjects have been awaken in slow wave sleep (SWS). In the present study, spectral analysis was applied during the last 10 min before and the first 10 min after awakening, and during 1 h after awakening while subjects performed the Stroop test. Seventeen subjects were divided into a Control group who slept 8 h, and a Sleep Deprived group who slept only 2 h. The results show that performance was normal in the Control group, whereas reaction time was increased during the first half hour and error level during the second half hour in the Sleep Deprived group. Spectral analysis applied on the waking EEG during the whole test session showed that alpha activity was increased in both groups, but theta power only in the Sleep Deprived group. There was a high positive correlation in sleep deprived subjects between delta power during the last 10 min of sleep and subsequent performance decrement in speed and accuracy. Comparison of individual records showed a high positive correlation between spectral power before and after awakening in the Control group (generally in the sense of an increased frequency band), but no correlation was found in the Sleep Deprived group who exhibited a rather disorganized pattern. We discuss these results in terms of incoherence in the EEG continuity during sleep offset after prior sleep loss, which could partly account for the performance decrement observed during SI in sleep deprived subjects.     

Yawning in morning and evening types

Yawning occurs more frequently in the early morning and in the late evening, close to sleep onset and after the awakening, and it might be linked to sleep propensity. We aimed to study yawning and its temporal distribution in morning and evening subjects who display different sleep-wake and sleepiness rhythms. Sixteen healthy young adults (8 evening-types and 8 morning-types, matched for age and gender) have been selected and instructed to keep their habitual sleep schedules and to signal every yawning occurrence for three consecutive days. Results show that evening-types yawn more frequently than morning-types, particularly during morning hours. Yawning frequency decreases across daytime in evening-types reaching its lowest level in the early evening and increases thereafter. Instead, in morning-types, yawning frequency remains quite low during daytime and increases in the evening. Moreover, both morning and evening types show a progressive increase of yawning frequency in the hours preceding sleep onset, whereas they differ after the awakening. Evening-types show a higher yawning frequency that remains quite stable in the hours following the awakening, while morning-types display a decline in yawning frequency. Our findings show that the temporal distribution of yawning frequency differs between chronotypes, supporting the hypothesis that differences in sleep-wake rhythm affect yawning, which could represent a behavioural sign of sleep propensity.     

Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women

STUDY OBJECTIVES: Examine age-adjusted odds and racial/ethnic differences in self-reported difficulties falling and staying asleep and early morning awakening in midlife women to determine whether difficulty sleeping increased with progression through the menopausal transition. DESIGN: Longitudinal analysis. SETTING: Community-based. PARTICIPANTS: 3,045 Caucasian, African American, Chinese, Japanese, and Hispanic women, aged 42-52 years and pre- or early peri-menopausal at baseline, participating in the Study of Women's Health Across the Nation (SWAN). Interventions: None. MEASUREMENTS AND RESULTS: Self-reported number of nights of difficulty falling asleep, staying asleep, and early morning awakening during the previous 2 weeks were obtained at baseline and 7 annual assessments. Random effects logistic regression was used to model associations between each of the 3 sleep measures and the menopausal transition, defined by bleeding patterns, vasomotor symptoms (VMS), and estradiol (E2) and follicle stimulating hormone (FSH) serum levels. Adjusted odds ratios (ORs) for difficulty falling asleep and staying asleep increased through the menopausal transition, but decreased for early morning awakening from late perimenopause to postmenopause. Naturally and surgically postmenopausal women using hormones, compared with those who were not, generally had lower ORs for disturbed sleep. More frequent VMS were associated with higher ORs of each sleep difficulty. Decreasing E2 levels were associated with higher ORs of trouble falling and staying asleep, and increasing FSH levels were associated with higher ORs of trouble staying asleep. Racial/ethnic differences were found for staying asleep and early morning awakening. CONCLUSIONS: Progression through the menopausal transition as indicated by 3 menopausal characteristics--symptoms, bleeding-defined stages, and endogenous hormone levels--is associated with self-reported sleep disturbances.