Circadian Adaptation to Night Shift Work Influences Sleep, Performance, Mood and the Autonomic Modulation of the Heart (original) (raw)
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Background. Epidemiologic evidence indicates that sleep loss may be a novel risk factor for cardiovascular diseases (CVDs); hypertension, coronary artery disease (CAD) and stroke. The increased risk of CVDs is possibly linked to the effect of sleep loss on hormones that play a major role in the central control of blood pressure and heart rate variability, also on angiotensin, cytokines, appetite and energy expenditure as well as sympathetic and vagal activity, melatonin and serotonin. Methods. Internet search and expert opinion from colleagues. Results. Exposure to light at night disturbs the circadian system with alterations of the sleep/activity patterns and suppression of melatonin production. Light is the most powerful synchronizer but, when exposure occurs at a time when the body would normally not be exposed to light, (that is, at night), then it disrupts the circadian rhythms. In developed countries, approximately, one fifth of the workers may have disruption of sleep due to night shift and may be unable to tolerate exposure to light during this time. Daily physiological variations include normal circadian rhythms which are interactive and require a high degree of phase positioning to produce subjective feelings of well being. Disturbances in these activities, may predispose circadian desynchronization, (whether from passage over time zones or from shift rotation), resulting in disturbance of the quantity and quality of sleep leading to hormonal and cardiovascular dysfunction. Shift work can increase the risk of CVD by several interrelated psychosocial, behavioral, and physiological mechanisms. Biological mechanisms are related to the activation of the autonomic nervous system, inflammation, dyslipidemia and glucose intolerance, which may increase the risk for atherosclerosis, metabolic syndrome and insulin resistance resulting in CAD, hypertension and stroke. It is important to promote greater changes in behavioural factors like physical activity, Mediterranean-style diet and meditation apart from providing rotation in shift to cover the loss of sleep. Conclusions. Disruption of sleep has become a public health problem due to industrialization and urbanization. Strategies to reduce the potential for circadian disruption, including extending the daily dark period, appreciating nocturnal awakening in the dark, using dim red light for R. B. Singh, B. Anjum, Rajiv Garg et al. 24 night-time necessities, and avoiding frequently rotating shifts. There is a need to have more intensive guidelines on dietary intakes, physical activity and meditation to prevent CVDs among subjects who have significant sleep disruption.
Circadian heart rate variability rhythm in shift workers
Journal of Electrocardiology, 1997
The objective of this study was to assess the influence of day-night cycle and sleep-awake period on the circadian pattern of heart rate variability (HRV). Twelve male oil refinery security shift workers, aged 39 _+ 7 years, 'were studied with 24-hour Holter monitor recordings during morning and :night work periods. Hourly HRV parameters in the time and frequency domains were evaluated. For both shifts, all HRV parameters during awake or work periods were found not to be statistically different. In both day and night work shifts, the very low frequency and high-frequency components of HRV and the proportion of differences in successive R-R intervals greater than 50 ms increased during the sleep period, while the low frequency/high frequency ratio decreased. The low-frequency component in absolute units and the SD of the R-R interval did not show any variation in either shifts for the different periods. These results suggest that the circadian pattern of HRV seems to be predominantly related to sleep (supine) and wakefulness (standing) and remains independent of night-day cycle. Key words: circadian rhythm, heart rate variability, shift workers, autonomic nervous system.
Melatonin Rhythms in Night Shift Workers
Sleep, 1992
For some time, it has remained uncertain whether the circadian rhythms of permanent night shift workers are adapted to their night-active schedule. Previous studies of this question have often been limited by "masking" (evoked) effects of sleep and activity on body temperature and cortisol, used as marker rhythms. In this study, the problem of masking was minimized by measuring the timing of melatonin production under dim light conditions. Nine permanent night shift workers were admitted to the Clinical Research Center (CRC) directly from their last work shift of the week and remained in dim light while blood samples were obtained hourly for 24 hours. Melatonin concentrations were measured in these samples using a gas-chromatographic mass-spectrometric method. Sleep diaries were completed for two weeks prior to the: admission to the CRC. Overall, the onset of the melatonin rhythm was about 7.2 hours earlier (or 16.8 hours late:r) in the night workers compared to day-active controls. It was not possible to know whether the phase of the melatonin rhythm was the result of advances or delays. In night shift workers, sleep was initiated (on average) about three hours prior to the onset of melatonin production. In contrast, day-active subjects initiated sleep (on average) about three hours after their melatonin onset. Thus, the sleep times selected by night shift workers may not be: well-synchronized to their melatonin rhythm, assumed to mark the phase of their underlying circadian pacemaker.
Permanent night work alters characteristics of circadian rhythm of rest--activity in human subjects
Biological Rhythm Research, 2008
The objective of this study was to explore the impact of permanent night shift on rest–activity rhythm in 20 randomly selected male permanent night workers, employed in a local newspaper printing office. The machine operators performed their job from 20:00 to 04:00 and the computer operators from 18:00 to 02:00 every day. The night workers availed one-day rest after working six consecutive days. Twenty-one age- and gender-matched day workers were also studied for comparison of rhythm parameters. In each subject rest–activity rhythm was monitored non-invasively by using Actiwatch (AW64 Mini Mitter Co. Inc., USA). Data were gathered at one-minute intervals for seven consecutive days. In addition, all subjects also responded to the morningness-eveningness questionnaire (Horne and Östberg's MEQ). Data were stored in the form of records and analyzed with the help of Actiware sleep software, Cosinor rhythmometry, Power spectrum analysis, Autocorrelation, ANOVA and Duncan's multiple range test, t-test and descriptive statistics. Rhythm parameters were computed at two different fixed windows, namely τ = 24 h and τ = 12 h. Harmonic means were calculated for those parameters obtained at both windows. All permanent night workers and day workers exhibited statistically significant circadian rhythm in rest–activity profile. At least five permanent night workers exhibited prominent non-circadian period. Statistically significant differences were observed between the rhythm characteristics of permanent night workers and day workers. The circadian 24-h average of activity in computer operators was significantly lower compared to that of the machine operators and day workers. Circadian amplitude of both machine operators and computer operators was significantly lower than that of day workers. Further, the peak appeared significantly later in machine operators (18.1 h) than that of the computer operators (16.8 h) and the day workers (10.9 h). The value of r24 was also lower in permanent night workers compared with that of the day workers. Results of this study conclusively demonstrate that permanent night shift alters circadian rhythm characteristics of rest–activity in night workers significantly and the changes were independent of the factors age and to the most extent chronotype. These might force permanent night workers to face negative health consequences in future.
Romanian Journal of Occupational Medicine, 2019
In many large cohort studies, the night shift constitutes a risk factor for developing cardiovascular disease and diabetes in workers. Current screening tests for people working in night shift include fasting glycaemia and electrocardiography. In fact, there are few studies focused on the description of the electrocardiographic changes after the night shift. This article describes the protocol of the “ECG modifications induced by the disturbance of the circadian rhythm in night-shift workers (ECGNoct)” study, which was initiated by the National Institute for Infectious Diseases “Prof. Dr. Matei Balș”. Nurses represent the target population. The protocol includes a full medical and occupational history, lifestyle habits (smoking, alcohol, nutrition), anthropometric and blood pressure measurements, blood tests (fasting glycemia, total cholesterol, triglycerides and high density lipoprotein cholesterol) and electrocardiogram recording. For nurses working in (night) shifts, we will reco...
2021
ABSTRACTNight shift work, characterized by behavioral circadian disruption, increases cardiometabolic disease risk. Our long-term goal is to develop a novel methodology to quantify behavioral circadian disruption in field-based settings and to explore relations to four metabolic salivary biomarkers of circadian rhythm. This pilot study enrolled 36 police academy trainees to test the feasibility of using wearable activity trackers to assess changes in behavioral patterns. Using a two-group observational study design, participants completed in-class training during dayshift for six weeks followed by either dayshift or nightshift field-training for six weeks. We developed a novel data-post processing step that improves sleep detection accuracy of sleep episodes that occur during daytime. We next assessed changes to resting heart rate (RHR) and sleep regularity index (SRI) during dayshift versus nightshift field training. Secondarily, we examined changes in field-based assessments of sa...
International Journal of Environmental Research and Public Health
Background: The effect of circadian disruption on the bio-psychological clock system has been widely studied. However, the mechanism and the association of circadian rhythm disruption with mental health and physiological responses are still unclear. Therefore, this study was conducted to investigate the effects of circadian rhythm disruption on mental health and physiological responses among shift workers and the general population. Methods: A total of 42 subjects participated in this quasi-experimental study. Participants were divided into a group of shift workers (n = 20) and a general population group (n = 22). Polysomnography tests, blood tests (cortisol, triglycerides and glucose), and psychological tests (Abbreviated Profile of Mood States, General Health Questionnaire-28, Working Memory and Processing Speed Indexes of the Wechsler Adult Intelligent Scale (WAIS-IV) were used to examine the effects of circadian rhythm disruption. Results: The results showed a significant relati...
Night work, chronotype and cortisol at awakening in female hospital employees
Scientific Reports, 2022
To examine the effect of night shift on salivary cortisol at awakening (C1), 30 min later (C2), and on the cortisol awakening response (CAR, the difference between C2 and C1). We compared shift and nonshift workers with a focus on the impact of worker chronotype. Our study included 66 shift-working females (mean age = 37.3 years, SD = 10.2) and 21 non-shift working females (mean age = 47.0 years, SD = 8.9). The shift workers collected their saliva samples at C1 and C2 on each two consecutive day shifts and night shifts. Non-shift workers collected their samples on two consecutive day shifts. We applied linear mixed-effects models (LMM) to determine the effect of night shift on CAR and logtransformed C1 and C2 levels. LMMs were stratified by chronotype group. Compared to non-shift workers, shift workers before day shifts (i.e. after night sleep) showed lower cortisol at C1 (exp (β) =0.58, 95% CI 0.42, 0.81) but not at C2. In shift workers, the CARs after night shifts (i.e. after day sleep) were lower compared to CARs before day shifts (β = − 11.07, 95% CI − 15.64, − 6.50). This effect was most pronounced in early chronotypes (early:
The Journal of physiology, 2018
Shift work is highly prevalent and is associated with significant adverse health impacts. There is substantial inter-individual variability in the way the circadian clock responds to changing shift cycles. The mechanisms underlying this variability are not well understood. We tested the hypothesis that light-dark exposure is a significant contributor to this variability; when combined with diurnal preference, the relative timing of light exposure accounted for 71% of individual variability in circadian phase response to night shift work. These results will drive development of personalised approaches to manage circadian disruption among shift workers and other vulnerable populations to potentially reduce the increased risk of disease in these populations. Night shift workers show highly variable rates of circadian adaptation. This study examined the relationship between light exposure patterns and the magnitude of circadian phase resetting in response to night shift work. In 21 part...