Working on atypical schedules

Shift work in nurses: contribution of phenotypes and genotypes to adaptation

BACKGROUND

Daily cycles of sleep/wake, hormones, and physiological processes are often misaligned with behavioral patterns during shift work, leading to an increased risk of developing cardiovascular/metabolic/gastrointestinal disorders, some types of cancer, and mental disorders including depression and anxiety. It is unclear how sleep timing, chronotype, and circadian clock gene variation contribute to adaptation to shift work.

METHODS

Newly defined sleep strategies, chronotype, and genotype for polymorphisms in circadian clock genes were assessed in 388 hospital day- and night-shift nurses.

RESULTS

Night-shift nurses who used sleep deprivation as a means to switch to and from diurnal sleep on work days (∼25%) were the most poorly adapted to their work schedule. Chronotype also influenced efficacy of adaptation. In addition, polymorphisms in CLOCK, NPAS2, PER2, and PER3 were significantly associated with outcomes such as alcohol/caffeine consumption and sleepiness, as well as sleep phase, inertia and duration in both single- and multi-locus models. Many of these results were specific to shift type suggesting an interaction between genotype and environment (in this case, shift work).

CONCLUSIONS

Sleep strategy, chronotype, and genotype contribute to the adaptation of the circadian system to an environment that switches frequently and/or irregularly between different schedules of the light-dark cycle and social/workplace time. This study of shift work nurses illustrates how an environmental "stress" to the temporal organization of physiology and metabolism can have behavioral and health-related consequences. Because nurses are a key component of health care, these findings could have important implications for health-care policy.

Model-based human circadian phase estimation using a particle filter

We present a method for tracking an individual's circadian phase that integrates dynamic models of circadian physiology with physiological measurements in a Bayesian statistical framework. A model of the circadian pacemaker's response to light exposure is transformed into a nonlinear state-space model with a circadian phase state. The probability distribution of the circadian phase is estimated by a particle filter that predicts changes over time based on the model, and performs updates with information gained from physiological measurements. Simulations demonstrate how probability distributions allow flexible initialization of model states and enable statistical quantification of entrainment and divergence properties of the circadian pacemaker. The combined use of sleep-wake scheduling data and physiological measurements is demonstrated in a case study highlighting advantages for addressing the challenge of noninvasive ambulatory monitoring of circadian physiology.

Hospital staff nurses' work hours, meal periods, and rest breaks. A review from an occupational health nurse perspective

Registered nurses are the largest group of health care providers in the United States. To provide 24-hour care, hospital staff nurses often work long hours and consecutive shifts, without adequate meal or rest breaks. Serious declines in functioning related to provider fatigue can lead to safety issues for patients and nurses alike. The occupational health nurse can assess the effects of nurses' work hours and break periods on employee health, educate staff on the importance of sleep and deleterious effects of fatigue, and implement programs to improve the work environment. This article examines nurses' work hours, break and meal period laws and regulations, and the role of the occupational health nurse in caring for this group of employees. Overall findings suggest that the expertise of an occupational health nurse in the hospital setting could significantly improve the health and safety of staff nurses.

Aspectos do regime de embarque, turnos e gestão do trabalho em plataformas offshore da Bacia de Campos (RJ) e sua relação com a saúde e a segurança dos trabalhadores

O artigo aborda pesquisa desenvolvida na indústria petrolífera offshore da Bacia de Campos (Rio de Janeiro, Brasil), campo empírico que acompanhamos de forma sistemática desde 2003 e que se situa no rol dos sistemas sociotécnicos complexos. Nosso objetivo é destacar os riscos potenciais associados à organização do trabalho, em especial o regime de embarque e o sistema de turnos adotados nas plataformas de petróleo por algumas das empresas atuantes na região. Isto porque entendemos que, no contexto investigado, os problemas relacionados à saúde - aí inclusos os que se situam na esfera mental - e à segurança dos trabalhadores possuem relação importante com aspectos da organização do trabalho, como aqueles que aqui se encontram em foco. Indicam-se proposições de mudança com o intuito de reduzir os impactos deletérios de tais fatores sobre a saúde e a segurança dos trabalhadores. A base teórico-metodológica utilizada na pesquisa se fundamenta, principalmente, no instrumental da Ergonomia da Atividade e da Psicodinâmica do Trabalho, numa perspectiva ergológica.

Hospital Staff Nurses' Work Hours, Meal Periods, and Rest Breaks

Registered nurses are the largest group of health care providers in the United States. To provide 24-hour care, hospital staff nurses often work long hours and consecutive shifts, without adequate meal or rest breaks. Serious declines in functioning related to provider fatigue can lead to safety issues for patients and nurses alike. The occupational health nurse can assess the effects of nurses' work hours and break periods on employee health, educate staff on the importance of sleep and deleterious effects of fatigue, and implement programs to improve the work environment. This article examines nurses' work hours, break and meal period laws and regulations, and the role of the occupational health nurse in caring for this group of employees. Overall findings suggest that the expertise of an occupational health nurse in the hospital setting could significantly improve the health and safety of staff nurses.

Using blue-green light at night and blue-blockers during the day to improves adaptation to night work: a pilot study

BACKGROUND

Bright light at night paired with darkness during the day seem to facilitate adaptation to night work. Considering the biological clock sensitive to short wavelengths, we investigated the possibility of adaptation in shift workers exposed to blue-green light at night, combined with using blue-blockers during the day.

METHODS

Four sawmill shift workers were evaluated during two weeks of night shifts (control and experimental) and one week of day shifts. Throughout the experimental week, ambient light (approximately 130 lx) was supplemented with blue-green light (200 lx) from 00:00 h to: 05:00 h on Monday and Tuesday, 06:00 h on Wednesday and 07:00 h on Thursday. Blue-blockers had to be worn outside from the end of the night shift until 16:00 h. For circadian assessment, salivary melatonin profiles were obtained between 00:00 h and 08:00 h, before and after 4 experimental night shifts. Sleep was continuously monitored with actigraphy and subjective vigilance was measured at the beginning, the middle and the end of each night and day shifts. The error percentage in wood board classification was used as an index of performance.

RESULTS

Through experimental week, melatonin profiles of 3 participants have shifted by at least 2 hours. Improvements were observed in sleep parameters and subjective vigilance from the third night (Wednesday) as performance increased on the fourth night (Thursday) from 5.14% to 1.36% of errors (p=0.04).

CONCLUSIONS

Strategic exposure to short wavelengths at night, and/or daytime use of blue-blocker glasses, seemed to improve sleep, vigilance and performance.

Sleep problems and workplace injuries in Canada

STUDY OBJECTIVE

To investigate the association between sleep problems and risk of work injuries among Canadian workers and to identify working groups most at risk for injuries.

DESIGN

Population-based cross-sectional survey.

SETTING

Canada Participants: Working-age respondents (15-64 years of age) who worked part or full-time in the last 12 months (n = 69,584).

INTERVENTIONS

None.

METHODS

This study used data from the Canadian Community Health Survey (CCHS) Cycle 1.1 2000-2001.

MEASUREMENTS AND RESULTS

The main indicator of sleep problems was reporting trouble going to sleep or staying asleep. Stratified logistic regression models were used to calculate odds ratios (OR) and 95% confidence intervals (CI) for the association of sleep problems and work injury after adjusting for potential confounders and for the survey design. Trouble sleeping most of the time was significantly associated with work injury in both men (OR = 1.25, 95% CI = 1.01-1.55) and women (OR = 1.54, 95% CI = 1.25-1.91). The multivariate stratified analysis found that men in trades and transportation jobs (OR = 1.50, 95% CI = 1.09-2.08), women in processing and manufacturing jobs (OR = 2.46, 95% CI = 1.11-5.47), and women who work rotating shifts (OR = 1.71, 95% CI = 1.11-2.64) were at the highest increased risk for work injury associated with trouble sleeping.

CONCLUSIONS

Trouble sleeping was associated with an increased risk of work injury. The number of injuries attributable to sleep problems was higher for women compared to men. While most job classes and shift types showed an increased risk of injury, some groups such as women in processing and manufacturing and those who work rotating shifts warrant further investigation and attention for intervention.

Microwave-assisted synthesis and structure-activity relationships of neuroactive pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivatives

We described herein the optimization of the synthetic methodology exploited to obtain the pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine sedative prototype 1a and novel analogues designed by successive molecular simplifications. By applying microwave irradiation during the hetero Diels-Alder key-step to obtain the heterotricyclic scaffold, under solvent-free conditions, we were able to obtain the desired compounds in drastically shorter times and better yields. Additionally, in vivo evaluation of the sedative effects of these heterocyclic derivatives showed that 1a and the novel structurally-related analogue 1e were the most efficient compounds to impair the locomotor activity in mice at the dose of 10micromol/kg.

Neurobiology of circadian systems

Time is a dimension tightly associated with the biology of living species. There are cycles of varied lengths in biological activities, from very short (ultradian) rhythms to rhythms with a period of approximately one day (circadian) and rhythms with longer cycles, of a week, a month, a season, or even longer. These rhythms are generated by endogenous biological clocks, i.e. time-keeping structures, rather than being passive reactions to external fluctuations. In mammals, the suprachiasmatic nucleus (SCN) is the major pacemaker. The pineal gland, which secretes melatonin, is the major pacemaker in other phyla. There also exist biological clocks generating circadian rhythms in peripheral tissues, for example the liver. A series of clock genes generates the rhythm through positive and negative feedback effect of proteins on their own synthesis, and this system oscillates with a circadian period. External factors serve as indicators of the astronomical (solar) time and are called zeitgebers, literally time-givers. Light is the major zeitgeber, which resets daily the SCN circadian clock. In the absence of zeitgebers, the circadian rhythm is said to be free running; it has a period that differs from 24 hours. The SCN, together with peripheral clocks, enables a time-related homeostasis, which can become disorganized in its regulation by external factors (light, social activities, food intake), in the coordination and relative phase position of rhythms, or in other ways. Disturbances of rhythms are found in everyday life (jet lag, shift work), in sleep disorders, and in several psychiatric disorders including affective disorders. As almost all physiological and behavioural functions in humans occur on a rhythmic basis, the possibility that advances, delays or desynchronization of circadian rhythms might participate in neurological and psychiatric disorders has been a theme of research. In affective disorders, a decreased circadian amplitude of several rhythms as well as a phase advance or delay have been described, leading to hypotheses about changes in biological clocks themselves or in their sensitivity to environmental factors, such as light or social cues. Molecular genetics studies have suggested the involvement of circadian clock genes, but no tight association has yet been found. Agomelatine is an antidepressant, agonist at melatonergic MT(1), MT(2) receptors and antagonist at 5-HT(2C) receptors, and is able to phase advance circadian rhythms in humans. The fact that non-pharmacological (light therapy, sleep deprivation, rhythm therapy) and pharmacological (lithium, antidepressants, agomelatine) therapies of affective disorders influence circadian rhythms indicates that biological clocks play a role in the pathophysiology of these disorders.

The regulation of central and peripheral circadian clocks in humans

Many circadian rhythms are controlled by the central clock of the suprachiasmatic nucleus of the hypothalamus, as well as clocks located in other brain regions and most peripheral tissues. These central and peripheral clocks are based on clock genes and their protein products. In recent years, the expression of clock genes has started to be investigated in human samples, primarily white blood cells, but also skin, oral mucosa, colon cells, adipose tissue as well as post-mortem brain tissue. The expression of clock genes in those peripheral tissues offers a way to monitor human peripheral clocks and to compare their function and regulation with those of the central clock, which is followed by markers such as melatonin, cortisol and core body temperature. We have recently used such an approach to compare central and peripheral rhythms in subjects under different lighting conditions. In particular, we have monitored the entrainment of the clock of blood cells in subjects undergoing a simulated night shift protocol with bright light treatment, known to efficiently reset the central clock. This line of research will be helpful for learning more about the human circadian system and to find ways to alleviate health problems of shift workers, and other populations experiencing altered circadian rhythms.

Circadian variability of cystatin C, creatinine, and glomerular filtration rate (GFR) in healthy men during normal sleep and after an acute shift of sleep

The estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with kidney disease and for the treatment of patients with medications that are eliminated by the kidneys. Plasma cystatin C has been shown in several studies to be superior to plasma creatinine for the estimation of GFR. However, there is limited information on the circadian variation of cystatin C and estimated GFR using cystatin C (eGFR(CystC)) or "The Modification of Diet in Renal Disease Study" (MDRD) (eGFR(MDRD)) equations. We studied the circadian variation of cystatin C and creatinine during night- and day-sleep conditions in seven healthy volunteers. Serum samples were collected every hour (48 samples per individual) to evaluate the effect of different sampling times on the test results. The median intra-individual coefficients of variations for the studied markers were 4.2% for creatinine, 4.7% for eGFR(MDRD), 5.5% for cystatin C, and 7.7% for eGFR(CystC). Neither cystatin C nor creatinine differed significantly between the night- and day-sleep conditions. Cystatin C differed significantly with time of day (p=.0003), but this was not the case for creatinine (p=.11). The circadian variation of cystatin C was minor. Small but significant increases in creatinine values and a decrease of eGFR(MDRD) were observed after food intake. Thus, cystatin C and creatinine sampling does not have to be restricted to specific times of the day.

Introduction: aging and the multifaceted influences on adaptation to working time

This special issue of Chronobiology International presents a selection of papers originally delivered at the 18th International Symposium on Shift Work and Working Time, held at Yeppoon, Australia, in August 2007. The key theme of the symposium was "Aging and Working Time: Creating Safe Environments." Older workers are widely believed to experience greater difficulty than younger workers adapting to shift work and irregular work schedules. However, while the three reviews of age effects published here (Costa & Di Milia, 2008; Folkard, 2008b; Gander & Signal, 2008) identify evidence that older workers do indeed adapt less well, they also demonstrate that much more research is urgently required. The remaining papers address various aspects of the impact of work schedules on health, safety, sleep, and performance. They can be divided into three broad categories: circadian and other periodic factors; sleep, sleepiness, and fatigue; and other aspects of health and adjustment. This collection of papers showcases the best of contemporary research on the safety and health effects of working hours, continuing the tradition established by the two previous issues of the journal devoted to earlier symposia on shift work and working time.

A practical approach to circadian rhythm sleep disorders

Circadian rhythm sleep disorders are common in clinical practice. The disorders covered in this review are delayed sleep phase disorder, advanced sleep phase disorder, free-running, irregular sleep-wake rhythm, jet lag disorder and shift work disorder. Bright light treatment and exogenous melatonin administration are considered to be the treatments of choice for these circadian rhythm sleep disorders. Circadian phase needs to be estimated in order to time the treatments appropriately. Inappropriately timed bright light and melatonin will likely worsen the condition. Measurements of core body temperature or endogenous melatonin rhythms will objectively assess circadian phase; however, such measurements are seldom or never used in a busy clinical practice. This review will focus on how to estimate circadian phase based on a careful patient history. Based on such estimations of circadian phase, we will recommend appropriate timing of bright light and/or melatonin in the different circadian rhythm sleep disorders. We hope this practical approach and simple recommendations will stimulate clinicians to treat patients with circadian rhythm sleep disorders.