Social Jetlag and Related Risks for Human Health: A Timely Review

The term social jetlag is used to describe the discrepancy between biological time, determined by our internal body clock, and social times, mainly dictated by social obligations such as school or work. In industrialized countries, two-thirds of the studying/working population experiences social jetlag, often for several years. Described for the first time in 2006, a considerable effort has been put into understanding the effects of social jetlag on human physiopathology, yet our understanding of this phenomenon is still very limited. Due to its high prevalence, social jetlag is becoming a primary concern for public health. This review summarizes current knowledge regarding social jetlag, social jetlag associated behavior (e.g., unhealthy eating patterns) and related risks for human health.

Association between circadian rhythm disruption and polycystic ovary syndrome

OBJECTIVE

To explore the association of circadian rhythm disruption with polycystic ovary syndrome (PCOS) and the potential underlying mechanism in ovarian granulosa cells (GCs).

DESIGN

Multicenter questionnaire-based survey, in vivo and ex vivo studies.

SETTING

Twelve hospitals in China, animal research center, and research laboratory of a women's hospital.

PATIENTS/ANIMALS

A total of 436 PCOS case subjects and 715 control subjects were recruited for the survey. In vivo and ex vivo studies were conducted in PCOS-model rats and on ovarian GCs collected from women with PCOS and control subjects.

INTERVENTION(S)

The PCOS rat model was established with the use of testosterone propionate.

MAIN OUTCOME MEASURE(S)

Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), RNA sequencing, rhythmicity analysis, functional enrichment analysis.

RESULT(S)

There was a significant correlation between night shift work and PCOS. PCOS-model rats presented distinct differences in the circadian variation of corticotropin-releasing hormone, adrenocorticotropic hormone, prolactin, and a 4-h phase delay in thyrotropic hormone levels. The motif enrichment analysis of ATAC-seq revealed the absence of clock-related transcription factors in specific peaks of PCOS group, and RNA sequencing ex vivo at various time points over 24 hours demonstrated the differential rhythmic expression patterns of women with PCOS. Kyoto Encyclopedia of Genes and Genomes analysis further highlighted metabolic dysfunction, including both carbohydrate and amino acid metabolism and the tricarboxylic acid cycle.

CONCLUSION(S)

There is a significant association of night shift work with PCOS, and genome-wide chronodisruption exists in ovarian GCs.

Genetic polymorphisms associated with circadian rhythm dysregulation provide new perspectives on bipolar disorder

OBJECTIVES

The objective of this study was to present a broad view of how genetic polymorphisms in genes that control the rhythmicity and function of circadian rhythm may influence the etiology, pathophysiology and treatment of bipolar disorder (BD).

METHODS

A bibliographic search was performed to identify and select papers reporting studies on variations in circadian genes and BD. A search of Medline, Google Scholar, Scopus, and Web of Science was carried out to review the literature.

RESULTS

Several studies provide evidence of contributions of variations in circadian genes to disease etiology, pathophysiological variations and lithium drug response. Dysfunction of the sleep-wake cycle, an important brain function regulator, is indicated as the primary means by which circadian gene variations act in mood disorders.

CONCLUSIONS

Investigations of the effects of circadian genes have suggested that the chronotype offers hope for guiding and improving management of patients with BD. However, BD is a disease of a complex nature and presents multiple endophenotypes determined by different associations between genetics and the environment. Thus, new genomic studies to delimit variations that may help improve the clinical condition of these patients are extremely important.

Night sleep influences white matter microstructure in bipolar depression

BACKGROUND

Alteration of circadian rhythms and sleep disruption are prominent trait-like features of bipolar disorder (BD). Diffusion tensor imaging (DTI) measures suggest a widespread alteration of white matter (WM) microstructure in patients with BD. Sleep promotes myelination and oligodendrocyte precursor cells proliferation. We hypothesized a possible association between DTI measures of WM microstructure and sleep quantity measures in BD.

METHODS

We studied 69 inpatients affected by a depressive episode in course of type I BD. We used whole brain tract-based spatial statistics on DTI measures of WM microstructure: axial, radial, and mean diffusivity (AD, RD, MD), and fractional anisotropy (FA). Self-assessed measures of time asleep (TA) and total sleep time (TST) were extracted from the Pittsburgh Sleep Quality Index (PSQI). Actigraphic recordings were performed on a subsample of 23 patients.

RESULTS

We observed a positive correlation of DTI measures of FA with actigraphic measures of TA and TST, and with PSQI measure of TA. DTI measures of RD inversely associated with actigraphic measure of TA, and with PSQI measures of TA and TST. Several WM tracts were involved, including corpus callosum, cyngulate gyrus, uncinate fasciculus, left superior and inferior longitudinal and fronto-occipital fasciculi, thalamic radiation, corona radiata, retrolenticular part of internal capsule and corticospinal tract.

LIMITATIONS

The study is correlational in nature, and no conclusion about a causal connection can be drawn.

CONCLUSIONS

Reduced FA with increased RD and MD indicate higher water diffusivity associated with less organized myelin and/or axonal structures. Our findings suggest an association between sleep disruption and these measures of brain microstructure in specific tracts contributing to the functional connectivity in BD.

Circadian Rhythm Dysregulation in Bipolar Spectrum Disorders

PURPOSE OF REVIEW

We review recent evidence for circadian rhythm dysregulation in bipolar spectrum disorders (BSDs). We examine evidence for endogenous abnormalities in the biological clock and disruptions in the external entrainment of circadian rhythms in BSDs. We also address whether circadian dysregulation provides vulnerability to onset of BSD and evidence for a new integration of reward and circadian dysregulation in BSD.

RECENT FINDINGS

Relative circadian phase delay (e.g., later melatonin peak, evening chronotype) is associated with BSD, particularly in the depressive phase. More consistent evidence supports irregularity of social rhythms, sleep/wake and activity patterns, and disruptions of social rhythms by life events, as stable trait markers of BSD and potential vulnerabilities for BSD onset. Growing research supports an integrative reward/circadian model. Both endogenous abnormalities in the biological clock pacemaking function and disruptions in the external entrainment of circadian rhythms by physical and social cues are involved in BSDs. Circadian dysregulation may provide vulnerability to BSD onset.

Disrupted Circadian Rhythm as a Common Player in Developmental Models of Neuropsychiatric Disorders

The environment in which individuals develop and mature is critical for their physiological and psychological outcome; in particular, the intrauterine environment has reached far more clinical relevance given its potential influence on shaping brain function and thus mental health. Gestational stress and/or maternal infection during pregnancy has been related with an increased incidence of neuropsychiatric disorders, including depression and schizophrenia. In this framework, the use of animal models has allowed a formal and deep investigation of causal determinants. Despite disruption of circadian clocks often represents a hallmark of several neuropsychiatric disorders, the relationship between disruption of brain development and the circadian system has been scarcely investigated. Nowadays, there is an increasing amount of studies suggesting a link between circadian system malfunction, early-life insults and the appearance of neuropsychiatric diseases at adulthood. Here, we briefly review evidence from clinical literature and animal models suggesting that the exposure to prenatal insults, i.e. severe gestational stress or maternal immune activation, changes the foetal hormonal milieu increasing the circulating levels of both glucocorticoids and pro-inflammatory cytokines. These two biological events have been reported to affect genes expression in experimental models and critically interfere with brain development triggering and/or exacerbating behavioural anomalies in the offspring. Herein, we highlight the importance to unravel the individual components of the body circadian system that might also be altered by prenatal insults and that may be causally associated with the disruption of neural and endocrine developmental programming.

Circadian Clocks as Modulators of Metabolic Comorbidity in Psychiatric Disorders

Psychiatric disorders such as schizophrenia, bipolar disorder, and major depressive disorder are often accompanied by metabolic dysfunction symptoms, including obesity and diabetes. Since the circadian system controls important brain systems that regulate affective, cognitive, and metabolic functions, and neuropsychiatric and metabolic diseases are often correlated with disturbances of circadian rhythms, we hypothesize that dysregulation of circadian clocks plays a central role in metabolic comorbidity in psychiatric disorders. In this review paper, we highlight the role of circadian clocks in glucocorticoid, dopamine, and orexin/melanin-concentrating hormone systems and describe how a dysfunction of these clocks may contribute to the simultaneous development of psychiatric and metabolic symptoms.

Circadian rest-activity rhythms predict future increases in depressive symptoms among community-dwelling older men

OBJECTIVE

Circadian rest-activity rhythms (CARs) have been cross-sectionally associated with depressive symptoms, although no longitudinal research has examined whether CARs are a risk factor for developing depressive symptoms.

METHODS

We examined associations of CARs (measured with actigraphy over a mean of 4.8 days) with depressive symptoms (measured with the Geriatric Depression Scale) among 2,892 community-dwelling older men (mean age: 76.2 ± 5.5 years) from the MrOS Sleep Study who were without cognitive impairment. Among 2,124 men with minimal (0-2) symptoms at baseline, we assessed associations between CAR parameters and increases to mild (3-5) or clinically significant (≥6) symptoms after an average of 1.2 (±0.32) years.

RESULTS

Cross-sectional associations between rhythm height parameters were independent of chronic diseases, lifestyle, sleep, and self-reported physical activity covariates. For example, men in the lowest mesor quartile had twice the adjusted odds (adjusted odds ratio [AOR]: 2.04, 95% confidence interval [CI]: 1.36-3.04, p = 0.0005) of having prevalent clinically significant symptoms (compared to minimal). Longitudinally, low CAR robustness (being in the lowest quartile of the pseudo-F statistic) was independently associated with increasing odds of developing symptoms (i.e., AOR for having clinically significant depressive symptoms at follow-up = 2.58, 95% CI: 1.11-5.99, p = 0.03).

CONCLUSION

CAR disturbances are indicative of depressive symptomology. Low CAR robustness may independently contribute to the risk of worsening depression symptomology.

The development and course of bipolar spectrum disorders: an integrated reward and circadian rhythm dysregulation model

In this article, we present and review the evidence for two major biopsychosocial theories of the onset and course of bipolar spectrum disorders (BSDs) that integrate behavioral, environmental, and neurobiological mechanisms: the reward hypersensitivity and the social/circadian rhythm disruption models. We describe the clinical features, spectrum, age of onset, and course of BSDs. We then discuss research designs relevant to demonstrating whether a hypothesized mechanism represents a correlate, vulnerability, or predictor of the course of BSDs, as well as important methodological issues. We next present the reward hypersensitivity model of BSD, followed by the social/circadian rhythm disruption model of BSD. For each model, we review evidence regarding whether the proposed underlying mechanism is associated with BSDs, provides vulnerability to the onset of BSDs, and predicts the course of BSDs. We then present a new integrated reward/circadian rhythm (RCR) dysregulation model of BSD and discuss how the RCR model explains the symptoms, onset, and course of BSDs. We end with recommendations for future research directions.

Sleep quality and body mass index in college students: the role of sleep disturbances

OBJECTIVE

Obesity and its comorbidities have emerged as a leading public health concern. The aim of this study was to explore the relationship between body mass index (BMI) and sleep patterns, including duration and disturbances.

METHODS

A convenience sample of 515 college students completed an online survey consisting of the Pittsburgh Sleep Quality Index (PSQI), and self-reported height and weight to calculate BMI. Univariate and multivariate logistic regression analyses were performed using components of the PSQI as predictors of overweight (BMI ≥ 25).

RESULTS

One-third of the participants had BMI ≥ 25, and 51% were poor-quality sleepers (PSQI > 5). Controlling for age and sex, only sleep disturbances were associated with overweight (odds ratio = 1.66, 95% confidence interval [1.08, 2.57]).

CONCLUSIONS

Sleep disturbances, rather than sleep duration, predicted overweight among young adults; this is consistent with the most recent evidence in the literature. These findings support expanding the scope of wellness programs to promote healthy sleep among students.

[Cognitive impairments in early restorative period of ischemic stroke]

The aim was to study prevalence and peculiarity of cognitive impairments in patients with ischemic stroke. 76 patients with stroke were examined in early restorative period of disease. Neurologic status of the patients was examined with NIHSS scale, Renkin scale was employed for measuring the degree of disability, MMSE and FAB was used to estimate cognitive functions. 24-hour, non-invasive ambulatory blood pressure (BP) monitoring was used to reveal arterial hypertension and impairment of circadian rhythm of ABP. Considerable prevalence of cognitive impairments was shown. 34.2% patients suffered from dementia. The most impaired cognitive functions were memory, calculation, repetition and writing. Risk factors of cognitive impairments in patients with ischemic stroke were advanced age, severe neurological impairments, increasing SBP, minimal DBP. Examination cognitive function after stroke is necessary to plan treatment, prevention and reablement.

Postoperative circadian disturbances

An increasing number of studies have shown that circadian variation in the excretion of hormones, the sleep wake circle, the core body temperature rhythm, the tone of the autonomic nervous system and the activity rhythm are important both in health and in disease processes. An increasing attention has also been directed towards the circadian variation in endogenous rhythms in relation to surgery. The attention has been directed to the question whether the circadian variation in endogenous rhythms can affect postoperative recovery, morbidity and mortality. Based on the lack of studies where these endogenous rhythms have been investigated in relation to surgery we performed a series of studies exploring different endogenous rhythms and factors affecting these rhythms. We also wanted to examine whether the disturbances in the postoperative circadian rhythms could be correlated to postoperative recovery parameters, and if pharmacological administration of chronobiotics could improve postoperative recovery. Circadian rhythm disturbances were found in all the examined endogenous rhythms. A delay was found in the endogenous rhythm of plasma melatonin and excretion of the metabolite of melatonin (AMT6s) in urine the first night after both minor and major surgery. This delay after major surgery was correlated to the duration of surgery. The amplitude in the melatonin rhythm was unchanged the first night but increased in the second night after major surgery. The amplitude in AMT6s was reduced the first night after minimally invasive surgery. The core body temperature rhythm was disturbed after both major and minor surgery. There was a change in the sleep wake cycle with a significantly increased duration of REM-sleep in the day and evening time after major surgery compared with preoperatively. There was also a shift in the autonomic nervous balance after major surgery with a significantly increased number of myocardial ischaemic episodes during the nighttime period. The circadian activity rhythm was also disturbed after both minor and major surgery. The daytime AMT6s excretion in urine after major surgery was increased on the fourth day after surgery and the total excretion of AMT6s in urine was correlated to sleep efficiency and wake time after sleep onset, but was not correlated to the occurrence of postoperative cognitive dysfunction. We could only prove an effect of melatonin substitution in patients with lower than median pain levels for a three days period after laparoscopic cholecystectomy. In the series of studies included in this thesis we have systematically shown that circadian disturbances are found in the secretion of hormones, the sleep-wake cycle, core body temperature rhythm, autonomic nervous system tone, myocardial ischaemia and activity rhythm after surgery. Correlation exists between circadian rhythm parameters and measures of postoperative sleep quality and recovery. However, oral melatonin treatment in the first three nights after surgery, cannot yet be generally recommended for improvement of sleep quality or other recovery parameters based on the available results. It may be indicated in subgroups or if other perioperative treatment algorithms were used, but this has to be investigated in future trials.

A pilot home study of temporal variations of symptoms in chronic obstructive lung disease

The purposes of this pilot study are to describe the 24-hr patterns of dyspnea, fatigue, and peak expiratory flow rate (PEFR) in patients with chronic obstructive pulmonary disease (COPD) and examine their interrelationships. The repeated-measures design protocol involved 10 patients with moderate to severe COPD who self-assessed dyspnea, fatigue, and PEFR five times a day for 8 days. Circadian rhythms were documented by single cosinor analysis in 40% of the participants for dyspnea, 60% for fatigue, and 60% for PEFR. The 8-day, 24-hr means of dyspnea and fatigue were moderately correlated; 70% of the sample displayed significant correlations. The means of PEFR and both dyspnea and fatigue were weakly negatively correlated. The findings suggest that circadian rhythm in lung function may not be temporally coupled with the circadian rhythm in dyspnea and fatigue in all patients and that the mean self-perceived levels of dyspnea and fatigue are moderately related.

The ascent into mania: a review of psychological processes associated with the development of manic symptoms

A comprehensive psychological account of the development of manic symptoms is needed to improve interventions for bipolar disorder. This review aims to develop the basis for such an account by covering three domains of evidence: (1) the multiple symptoms of mania; (2) the signs and symptoms leading up to mania; (3) the psychological processes associated with bipolar disorder, in particular during elevated mood states. It is concluded that the development of mania is characterised by a core experience of psychomotor activation that builds up over time and is associated with, and potentially enhanced by, increased processing of internally generated evaluative (positive and negative) information about the self and close others. The challenge of a theoretical account is to explain this dynamic process and predict how different symptom profiles develop over time within different individuals.

Cortisol circadian rhythm alterations in psychotic major depression

BACKGROUND

Increased hypothalamic-pituitary-adrenal axis activity is well described in psychotic depression with an emphasis on 24-hour, urinary free cortisol levels or dexamethasone suppression tests. There are limited data on cortisol levels during specific times of the day.

METHODS

Patients with depression with (PMD) and without (NPMD) psychosis and healthy control subjects were studied using rating scales of depression and psychosis and measures of HPA activity, including overnight cortisol and adrenocorticotropin levels. We used analysis of variance to determine group differences and regression analyses to assess contributions of specific measures to cortisol levels.

RESULTS

PMDs had higher cortisol during the evening hours than did NPMDs or control subjects, who did not differ from one another. Regression analyses suggest that depression and the combination of depressive and psychotic symptoms were important contributors to variance in evening cortisol.

CONCLUSIONS

PMD is associated with increased cortisol levels during the quiescent hours. Enhanced cortisol activity, particularly a higher nadir, was related to depression severity and the interaction of depressive and psychotic symptoms. This increase suggests a defect in the action of the circadian timing system and HPA axis, creating a hormonal milieu similarly seen in early Cushing's syndrome and potentially an (im)balance of mineralocorticoid and glucocorticoid receptor activity.

[Psychological stress in oncology: the role of glucocorticoids]

During the last years, the correlations between biological processes, psychological adjustment and stress disorders have received increasing attention and a growing body of research results has been published in the general literature. In the realm of psycho-oncology, however, conceptual models on this topic and studies aimed at their validation have remained relatively scanty. On the basis of our observations and available literature in the field of post-traumatic and depressive stress disorders in oncology, we have proposed to apply the concept of allostatic load to the study and understanding of the psychological experience of cancer. This strategy has led us to the formulation of a novel classification of adjustment disorders in oncology and the creation of the clinical entity named "cancer-specific stress syndrome". Depending on clinical presentation of the syndrome, one distinguishes three subtypes, namely the depressive, post-traumatic and "dysallostatic" (mixed) forms. In the present paper, we examine the role of glucocorticoids and their relationships with one of the basic components of allostatic load--a failure to counter-regulate the immune system by the hypothalamic-pituitary-adrenal axis--in the physiopathology of stress disorders in oncology. Conflicting theories are presented--glucocorticoid cascade versus insufficient glucocorticoid signal transmission--and studies measuring potential correlations between stress and cortisol in oncology are critically reviewed. The results of this process provide substantial support for the application of the allostatic load model and post-traumatic phenomenology, but important advances have yet to be achieved before definitive conclusions can be established in this field. Such advances could lead to profound changes in the way we understand and treat psychological distress in patients with cancer, both pharmacologically and psychotherapeutically.

Socioeconomic status, race, and diurnal cortisol decline in the Coronary Artery Risk Development in Young Adults (CARDIA) Study

OBJECTIVES

The objectives of this study were to assess whether socioeconomic status (SES) is associated with dysregulation of the cortisol diurnal rhythm and whether this association is independent of race and occurs equally in whites and blacks; and to determine if an association between SES and cortisol can be explained (is mediated) by behavioral, social, and emotional differences across the SES gradient.

METHODS

Seven hundred eighty-one subjects from a multisite sample representing both whites and blacks provided six saliva cortisol samples over the course of the day: at awakening, 45 minutes, 2.5 hours, 8 hours, and 12 hours after awakening, and at bedtime.

RESULTS

Both lower SES (education and income) and being black were associated with higher evening levels of cortisol. These relationships were independent of one another and SES associations with cortisol were similar across racial categories. The evidence was consistent with poorer health practices (primarily smoking), higher levels of depressive symptoms, poorer social networks and supports, and feelings of helplessness (low mastery) mediating the link between SES and cortisol. However, we found no evidence for psychosocial or behavioral mediation of the association between race and cortisol response.

CONCLUSIONS

Lower SES was associated in a graded fashion with flatter diurnal rhythms as a result of less of a decline during the evening. This association occurred independent of race and the data were consistent with mediation by health practices, emotional and social factors. Blacks also showed a flatter rhythm at the end of the day. This association was independent of SES and could not be explained by behavioral, social, or emotional mediators.

Subjective and predicted sleepiness while driving in young adults

Sleepiness is a significant contributor to car crashes and sleepiness related crashes have higher mortality and morbidity than other crashes. Young adult drivers are at particular risk for sleepiness related car crashes. It has been suggested that this is because young adults are typically sleepier than older adults because of chronic sleep loss, and more often drive at times of increased risk of acute sleepiness. This prospective study aimed to determine the relationship between predicted and perceived sleepiness while driving in 47 young-adult drivers over a 4-week period. Sleepiness levels were predicted by a model incorporating known circadian and sleep factors influencing alertness, and compared to subjective ratings of sleepiness during 2518 driving episodes. Results suggested that young drivers frequently drive while at risk of crashing, at times of predicted sleepiness (>7% of episodes) and at times they felt themselves to be sleepy (>23% of episodes). A significant relationship was found between perceived and predicted estimates of sleepiness. However, the participants nonetheless drove at these times. The results of this study may help preventative programs to specifically target factors leading to increased sleepiness when driving (particularly time of day), and to focus interventions to stop young adults from driving when they feel sleepy.

The empirical status of melancholia: Implications for psychology

The concept of a subtype of depression with a biological rather than a psychological set of causes has been more prominent in the psychiatric literature than in the psychological literature on depression. There has been dispute as to whether research on melancholia supports the distinction of a separate subtype with a distinct symptomatic profile characterized by marked anhedonia, psychomotor difficulties, excessive guilt or hopelessness, suicidal features, and appetite and weight disturbances. Research suggests that individuals with melancholic depression are qualitatively different from those with non-melancholic depression in their symptomatology. Examination of biological functioning, personality traits, responsiveness to treatment, and suicidality also tend to support the melancholic-non-melancholic distinction. This paper reviews the status of the melancholia concept and explores its implications for psychological research and practice.

Mood regulation in seasonal affective disorder patients and healthy controls studied in forced desynchrony

In healthy subjects, both the duration of wakefulness and the circadian pacemaker have been demonstrated to be involved in the regulation of mood. Some features of affective disorders suggest that these two factors also play a role in the dysregulation of mood. In particular, disturbances of the circadian pacemaker have been proposed to be a pathogenetic factor in Seasonal Affective Disorder, winter type (SAD). This report presents a test of this proposition. To this end seven SAD patients and matched controls were subjected to a 120-h forced desynchrony protocol, in which they were exposed to six 20-h days. This protocol enables us to discriminate the extent to which the course of mood is determined by the imposed 20-h sleep-wake cycle from the influence of the circadian pacemaker on that course. Patients participated during a depressive episode, after recovery upon light therapy and in summer. Controls were studied in winter and in summer. Between SAD patients and controls no significant differences were observed in the period length nor in the timing of the endogenous circadian temperature minimum. In both groups, sleep-wake cycle- and pacemaker-related components were observed in the variations of mood, which were not significantly different between conditions.

Psychiatric features and disturbance of circadian rhythm of temperature, pulse, and blood pressure in Wilson's disease

Wilson's disease (hepatolenticular degeneration), a disease of genetic origin, is due to abnormal copper metabolism affecting many organs and systems, especially the liver and the nervous system. The initial symptoms can be exclusively or predominantly psychiatric, including psychotic features. Three cases are reported in which the clinical picture at the beginning was compatible with a psychiatric diagnosis. During hospitalization, before treatment, there were abnormal and spontaneous changes in the circadian rhythm of temperature, pulse, and blood pressure, recorded every 6 hours, with febrile peaks in the absence of infectious focus. Because the hypothalamus is important in the regulation of these autonomic functions, the hypothesis of a possible hypothalamic dysfunction was made, justifying a wide clinical and laboratory investigation that allowed the diagnosis of Wilson's disease. Alertness to circadian rhythm abnormalities in such cases may help the psychiatrist avoid an erroneous diagnosis.

The impact of shift patterns on healthcare professionals

Aim To compile a literature review of studies on shift work which have relevance to the management of health services personnel. Background In the National Health Service it has always been necessary for certain areas, for example, in-patient services, to provide 24-hour service and hence shift work has been very much a feature of the organization. There is much anecdotal evidence of staff suffering from adverse physical, psychological and social problems that are attributed to the shift patterns they work in. Method The literature review includes studies which cite evidence of the benefits or not for the differing lengths of shifts and shift rotation, particularly in relation to circadian rhythms. The literature reviewed highlighted the consequences of shift work as it affects sleep, eating and social patterns, and physical and mental health. Findings There are some compensatory behaviours to help staff better cope with working shifts and the research base for these is reviewed. Conclusions The paper concludes with recommendations to inform decision-making by nurse managers responsible for the completion of duty rotas in health service provision.