Relationship of work schedules to gastrointestinal diagnoses, symptoms, and medication use in auto factory workers

Eating during the biological night is associated with nausea

OBJECTIVES

This study assessed whether there was a time-of-day effect on nausea reports in participants during studies employing circadian protocols.

METHODS

Visual-analog-scales of nausea ratings were recorded from 34 participants (18-70years; 18 women) during forced desynchrony studies, where meals were scheduled at different circadian phases. Subjective nausea reports from a further 81 participants (18-35years; 36 women) were recorded during constant routine studies, where they ate identical isocaloric hourly snacks for 36-40 hours.

RESULTS

Feelings of nausea varied by circadian phase in the forced desynchrony studies, peaking during the biological night. Nausea during the constant routine was reported by 27% of participants, commencing 2.9 ± 5.2 hours after the midpoint of usual sleep timing, but was never reported to start in the evening (4-9 PM).

CONCLUSIONS

Nausea occurred more often during the biological night and early morning hours. This timing is relevant to overnight and early morning shift workers and suggests that a strategy to counteract that is to pay careful attention to meal timing.

Seasonal influence on cognitive and psycho-physiological responses to a single 11-h day of work in outdoor mine industry workers

This study investigated the seasonal effects that working outdoors had on various parameters in mining industry workers over the course of a work-shift. Workers (n = 27) were assessed in summer (33.3 ± 4.2°C, 38 ± 18% RH; n = 13, age = 46 ± 14 y, BMI = 29.1 ± 5.7 kg/m2) and winter (23.6 ± 5.1°C, 39 ± 20% RH; n = 14, age = 44 ± 12 y, BMI = 31.2 ± 4.1 kg/m2). Core temperature and heart-rate were measured continuously (analyzed at five time points), while perceptual measures, cognitive and manual dexterity performance were assessed at various times over an 11-h shift at the start of a 14-day swing. Hydration was assessed (urine specific gravity) pre- and post-shift. Working memory was impaired in summer compared to winter (-10%; p = 0.039), however did not change throughout the shift. Processing efficiency was significantly reduced at 12 pm (-12%; p = 0.005) and 5 pm (-21%; p < 0.001) compared to 9 am, irrespective of season (p > 0.05). Manual dexterity (dominant-hand) improved over the shift (+13%, p = 0.002), but was not different between seasons. Perceived fatigue had no main effect of season or shift. Core temperature, heart-rate, thermal sensation and rating of perceived exertion increased throughout the shift, with only core temperature and thermal sensation showing a seasonal effect (summer: +0.33°C, +18%, respectively; p < 0.002). Notably, 23% of workers in summer and 64% in winter started work significantly dehydrated, with 54% and 64% in summer and winter, respectively, finishing work with significant to serious dehydration. Impairment in working memory in summer combined with high levels of dehydration over the work-shift reinforces the need for workplace education on the importance of hydration and risk of occupation heat stress. Abbreviations: Core temperature: Tc; Fly-in fly-out: FIFO; Ratings of perceived exertion: RPE; Relative humidity: RH; Urinary specific gravity: USG; Wet bulb globe temperature: WBGT.

Bowel Health in U.S. Shift Workers: Insights from a Cross-Sectional Study (NHANES)

Working outside of regular daytime hours is increasingly common in current societies and poses a substantial challenge to an individual’s biological rhythm. Disruptions of the gastrointestinal tract’s circadian rhythm and poor dietary choices subsequent to shiftwork may predispose the shift workforce to an increased risk of gastrointestinal disorders, including constipation, peptic ulcer disease, and erosive gastritis. We investigated bowel health in a US population of shift workers, using data from the National Health and Nutrition Examination Survey, and compared bowel movement (BM) frequency and defecation patterns between 2007 day workers and 458 shift workers (representing 55,305,037 US workers). Using bivariate and multivariate logistic regression techniques, our results suggested no association between shiftwork status and BM frequency, bowel leakage of gas, and stool consistency. Constipation prevalence was high but comparable in both groups (6.90% vs. 7.09%). The low fiber intake observed in both groups (15.07 vs. 16.75 g/day) could play a potential role here. The two groups did not differ with regard to other nutrients that may influence BM frequency and stool consistency (e.g., carbohydrate or caffeine intake). Additional studies including food group analyses and fecal biomarkers are warranted for a better understanding of GI health in shift workers.

Circadian Rhythms and Melatonin Metabolism in Patients With Disorders of Gut-Brain Interactions

Circadian rhythms are cyclic patterns of physiological, behavioural and molecular events that occur over a 24-h period. They are controlled by the suprachiasmatic nucleus (SCN), the brain’s master pacemaker which governs peripheral clocks and melatonin release. While circadian systems are endogenous, there are external factors that synchronise the SCN to the ambient environment including light/dark cycles, fasting/fed state, temperature and physical activity. Circadian rhythms also provide internal temporal organisation which ensures that any internal changes that take place are centrally coordinated. Melatonin synchronises peripheral clocks to the external time and circadian rhythms are regulated by gene expression to control physiological function. Synchronisation of the circadian system with the external environment is vital for the health and survival of an organism and as circadian rhythms play a pivotal role in regulating GI physiology, disruption may lead to gastrointestinal (GI) dysfunction. Disorders of gut-brain interactions (DGBIs), also known as functional gastrointestinal disorders (FGIDs), are a group of diseases where patients experience reoccurring gastrointestinal symptoms which cannot be explained by obvious structural abnormalities and include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Food timing impacts on the production of melatonin and given the correlation between food intake and symptom onset reported by patients with DGBIs, chronodisruption may be a feature of these conditions. Recent advances in immunology implicate circadian rhythms in the regulation of immune responses, and DGBI patients report fatigue and disordered sleep, suggesting circadian disruption. Further, melatonin treatment has been demonstrated to improve symptom burden in IBS patients, however, the mechanisms underlying this efficacy are unclear. Given the influence of circadian rhythms on gastrointestinal physiology and the immune system, modulation of these rhythms may be a potential therapeutic option for reducing symptom burden in these patients.

Chronic Jet Lag Exacerbates Jejunal and Colonic Microenvironment in Mice

Background

Evidence suggests that circadian rhythm disorder is associated with a variety of gastrointestinal diseases, and the circadian rhythm plays a key role in maintaining the homeostasis of intestinal flora. The underlying mechanisms are still not completely identified. This study was aimed to explore whether jet lag-caused circadian disruption influences gut microbiome and its metabolites.

Methods

Mice were synchronized with 12-h light/dark cycles (control group) or subjected to daily 8-h advance of the light/dark cycle for every 3 days (jet-lagged group). Four months later, fecal samples and jejunal contents were collected and analyzed by 16S rRNA gene sequencing. In addition, fecal samples were subjected to metabolome analysis with ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS).

Results

The results of 16s rRNA sequencing showed that chronic jet lag led to decreased microbial abundance, richness, and diversity in both feces and jejunal contents. ANOSIM analysis revealed significant difference between control and jet-lagged groups. As the colonic microbiome, the abundance of Bacteroidetes phylum was significantly decreased and that of Actinobacteria phylum was increased in jet-lagged mice. Jet lag increased the ratio of Firmicutes to Bacteroidetes, an indicator for the imbalance of gut microbiota. Metabolome analysis of fecal samples showed that the levels of tryptophan and its derivatives were decreased in jet-lagged mice. In addition, fecal levels of secondary bile acids changed under jet lag conditions. Correlation analysis identified associations between tryptophan (and its derivatives) levels and colonic microbiota.

Conclusions

This study presents a comprehensive landscape of gut microbiota and its metabolites in mice subjected to chronic jet lag. The results suggest that circadian disruption may lead to changes in fecal and jejunal microbiota and fecal metabolites. Moreover, our results demonstrate a novel interplay between the gut microbiome and metabolome.

Differences between fixed day shift workers and rotating shift workers in gastrointestinal problems: a systematic review and meta-analysis

This study comprised a review and compilation of literature to gain an in-depth understanding of the impact of rotating shift work on gastrointestinal health. PubMed, CINAHL, and the Cochrane Library were searched for studies published between January 1, 1985, and June 30, 2020. Fixed day shifts were defined as work shifts that began between 7:00 and 9:00 in the morning. Shifts beginning at any other time were classified as rotating shifts. A meta-analysis was performed using Comprehensive Meta-Analysis Software (CMA) version 3. In the end, 16 studies were included in the meta-analysis. An odds ratio (OR) of 1.56 (95% confidence interval (CI): 1.24-1.95), indicating that gastrointestinal problems are more common in rotating shift workers than in fixed day shift workers. Four gastrointestinal problems, namely, irritable bowel syndrome, constipation, indigestion, and peptic ulcers, were then analyzed separately. Significant differences between rotating shift workers and fixed day shift workers were found only for indigestion and peptic ulcers. For indigestion, the OR was 1.72 (95% CI: 1.28-2.30). For peptic ulcers, the OR was 1.66 (95% CI: 1.19-2.30). Thus, research indicates that rotating shift work may increase the risk of gastrointestinal problems, particularly indigestion and peptic ulcers.

Sleep Characteristics and Rest-Activity Rhythms Are Associated with Gastrointestinal Symptoms Among Adults with Inflammatory Bowel Disease

BACKGROUND

Sleep disturbance is common in inflammatory bowel disease (IBD) and is associated with poorer quality of life and increased disease activity; however, sleep is a multidimensional process, and little is known about specific sleep characteristics and rest-activity rhythms (RARs) in this population.

AIMS

The purposes were to (1) describe sleep characteristics and RARs; (2) compare sleep characteristics and RARs and GI symptoms by disease activity; and (3) describe associations between sleep characteristics, RARs, and GI symptoms among adults with IBD.

METHODS

We conducted a cross-sectional study of adults with IBD. We measured sleep characteristics and RARs (continuous wrist actigraphy); GI symptoms (PROMIS-GI); and disease activity (physicians' global assessment). We conducted cosinor and nonparametric analyses to compute RAR variables and bivariate analyses to address the aims.

RESULTS

The sample included 37 participants [age M = 38 years (SD = 13.8) and 21 (56.8%) female], of whom 23 (60.6%) were in remission. Sleep efficiency [M = 82.91% (SD 5.35)] and wake after sleep onset (WASO) [M = 42.26 min (SD 18.57)] were not associated with disease activity. Inter-daily stability of the RAR was associated with heartburn/reflux (r = - .491, p = .005) and gas/bloating (r = - .469, p = .008). Intra-daily variability of the RAR was associated with heartburn/reflux (r = .421, p = .018).

CONCLUSIONS

People with IBD may have disrupted RARs, which are associated with GI symptoms. Research is needed to improve understanding of these associations and to develop interventions to improve these characteristics in adults with IBD.

Time after time: circadian clock regulation of intestinal stem cells

Daily fluctuations in animal physiology, known as circadian rhythms, are orchestrated by a conserved molecular timekeeper, known as the circadian clock. The circadian clock forms a transcription-translation feedback loop that has emerged as a central biological regulator of many 24-h processes. Early studies of the intestine discovered that many digestive functions have a daily rhythm and that intestinal cell production was similarly time-dependent. As genetic methods in model organisms have become available, it has become apparent that the circadian clock regulates many basic cellular functions, including growth, proliferation, and differentiation, as well as cell signalling and stem cell self-renewal. Recent connections between circadian rhythms and immune system function, and between circadian rhythms and microbiome dynamics, have also been revealed in the intestine. These processes are highly relevant in understanding intestinal stem cell biology. Here we describe the circadian clock regulation of intestinal stem cells primarily in two model organisms: Drosophila melanogaster and mice. Like all cells in the body, intestinal stem cells are subject to circadian timing, and both cell-intrinsic and cell-extrinsic circadian processes contribute to their function.

Circadian rhythms: a regulator of gastrointestinal health and dysfunction

Circadian rhythms regulate much of gastrointestinal physiology including cell proliferation, motility, digestion, absorption, and electrolyte balance. Disruption of circadian rhythms can have adverse consequences including the promotion of and/or exacerbation of a wide variety of gastrointestinal disorders and diseases. Areas covered: In this review, we evaluate some of the many gastrointestinal functions that are regulated by circadian rhythms and how dysregulation of these functions may contribute to disease. This review also discusses some common gastrointestinal disorders that are known to be influenced by circadian rhythms as well as speculation about the mechanisms by which circadian rhythm disruption promotes dysfunction and disease pathogenesis. We discuss how knowledge of circadian rhythms and the advent of chrono-nutrition, chrono-pharmacology, and chrono-therapeutics might influence clinical practice. Expert opinion: As our knowledge of circadian biology increases, it may be possible to incorporate strategies that take advantage of circadian rhythms and chronotherapy to prevent and/or treat disease.

Sleep Disturbances Are Commonly Reported Among Patients Presenting to a Gastroenterology Clinic

BACKGROUND

Poor sleep quality is common among patients with gastrointestinal (GI) disorders. However, few studies have assessed the presence of insomnia or reported circadian preferences and none have directly compared sleep between common GI conditions.

AIMS

To compare clinical sleep characteristics in patients presenting to a tertiary care GI clinic for irritable bowel syndrome (IBS), functional dyspepsia (FD), inflammatory bowel disease (IBD), gastroesophageal reflux disease (GERD), and celiac disease (CD).

METHODS

Validated sleep measures were administered to consecutive patients if they were diagnosed with IBS, IBD in clinical remission, CD, FD, or GERD. Healthy Controls (HCs) with no reported GI diagnoses or symptoms were also recruited.

RESULTS

A total of 212 eligible respondents completed this survey, 161 GI clinic patients (IBS (n = 48), GERD (n = 29), IBD in clinical remission (n = 44), CD (n = 40)), and 41 HCs. Only, 10 respondents had a diagnosis of FD, and these were excluded. The IBS group had the highest frequency of poor sleep (72%) followed by CD (61%), GERD (60%), IBD (54%), and HC (39%). IBS patients also had the highest frequency of clinical insomnia (51%), followed by GERD (37%), CD (35%), IBD (27%), and HC (18%). 40% of IBS patients reported taking sleep medications at least once per week, compared to 32% of GERD, 23% IBD, 13% CD, and 15% HC.

CONCLUSIONS

Patients presenting to a tertiary care GI clinic report poorer sleep than healthy controls. In general, patients with IBS report the highest rates of sleep difficulties compared to patients with other diagnoses.

Effects of Clockwise and Counterclockwise Job Shift Work Rotation on Sleep and Work-Life Balance on Hospital Nurses

Rotational shift work is associated with sleep disturbances, increased risk of cardiovascular and psychological disorders, and may negatively impact work⁻life balance. The direction of shift rotation (Clockwise, CW or counterclockwise, CCW) and its role in these disorders are poorly understood. The aim of the study was to investigate the effect of the shift schedule direction on sleep quantity and quality, alertness and work performance, and on work⁻life balance on hospital nurses. One-hundred female nurses, working a continuous rapid shift schedule in hospitals in the north of Italy, participated in this cross-sectional study. Fifty worked on CW rotation schedule (Morning: 6 a.m.⁻2 p.m., Afternoon: 2 p.m.⁻10 p.m., Night: 10 p.m.⁻6 a.m., 2 rest days) and fifty on CCW rotation (Afternoon, Morning, Morning, Night, 3 rest days). Data were collected by ad hoc questionnaire and daily diary. During the shift cycle CW nurses slept longer (7.40 ± 2.24 h) than CCW (6.09 ± 1.73; p < 0.001). CW nurses reported less frequently than CCW awakening during sleep (40% vs. 80%; p < 0.001), attention disturbance during work (20% vs. 64%; p < 0.001), and interference with social and family life (60% vs. 96% and 20% vs. 70%, respectively; p < 0.001). CCW rotating shift schedule seems to be characterized by higher sleep disturbances and a worse work⁻life balance.

The impact of long working hours on the health of German employees

Excessive working hours have negative consequences for employees’ health. Looking deeper into this problem, this article examines how employers’ needs for more intense working or more flexible working hours affect their employees’ psychosomatic health. A German representative survey of 13,452 full-time employees found that long working hours, work intensity (deadline and performance pressure) and flexibility requirements (permanent availability, changes in working hours) were significantly related to psychosomatic health complaints. When considering future work design and practices, these findings show which unfavourable working conditions are to be avoided to maintain the psychosomatic health of employees.

The Relationship Between Shift Work and Men's Health

BACKGROUND

More than 21 million Americans and nearly 20% of the U.S. workforce are shift workers. Non-standard shift work, defined as work that falls outside of 6 am-6 pm, can lead to poor diet, exercise, and sleep habits that lead to decreased productivity, increased workplace accidents, and a variety of negative health outcomes.

AIM

To investigate the associations between shift work exposure and chronic medical conditions such as metabolic syndromes, cardiovascular disease, gastrointestinal disturbances, and depression as well as urologic complications including hypogonadism, male infertility, lower urinary tract symptoms, and prostate cancer with a focus on the effects of shift work sleep disorder (SWSD) on the severity of these negative health outcomes.

METHODS

We reviewed the literature examining effects of shift work and SWSD on general and urologic health.

OUTCOMES

We produced a summary of effects of shift work on health with focus on the increased risk of negative health outcomes in non-standard shift workers, particularly those with SWSD, when compared to daytime workers or workers without SWSD.

RESULTS

Studies have associated non-standard shift work schedules and poor health outcomes, including increased risks of diabetes mellitus, dyslipidemia, hypertension, heart disease, peptic ulcer disease, and depression, in shift workers. However, few studies have focused on the role that shift work plays in men's urologic health. Current evidence supports associations between non-standard shift work and increased hypogonadal symptoms, poor semen parameters, decreased fertility, lower urinary tract symptoms, and prostate cancer. These associations are strengthened by the presence of SWSD, which affects up to 20% of shift workers. Unfortunately, interventions, such as planned naps, timed light exposure, melatonin, and sedative hypnotics, aimed at alleviating excessive nighttime sleepiness and daytime insomnia in non-standard shift workers experiencing SWSD, are limited and lack strong evidence to support their efficacy.

CONCLUSIONS

Non-standard shift work has been associated with a variety of negative health outcomes and urologic complications, especially with concurrent SWSD. Recognition of these increased risks among shift workers can potentially aid in more effective screening of chronic health and urologic conditions. Non-pharmacologic treatment of SWSD focuses on behavioral therapy and sleep hygiene while melatonin, hypnotics, and stimulants are used to alleviate insomnia and excessive sleepiness of SWSD. Further research into both pharmacologic and non-pharmacologic therapies for SWSD is needed to establish more definitive guidelines in the treatment of SWSD in order to increase productivity, minimize workplace accidents, and improve quality of life for shift workers. Deng N, Kohn TP, Lipshultz LI, et al. The Relationship Between Shift Work and Men's Health. Sex Med Rev 2018;6:446-456.

A Review of Medication Use as an Indicator of Human Health Impact in Environmentally Stressed Areas

We reviewed from literature the feasibility of medication use as an indicator of health outcomes in environmentally stressed areas, especially where a paucity of typical epidemiological and other risk-based data are encountered. The majority of studies reported were about medication use as an indicator of adverse respiratory effects from air pollution in developed countries. Studies to a lesser extent pointed to medication use as indicator of health outcomes associated with other environmental health stressors such as water, noise pollution, and habitat conditions. The relationship between environmental stressors and medication use strongly suggests that medication use could be used to measure the impact of environmental stressors that otherwise could not be measured by epidemiological or other impact assessment studies, typically in settings where morbidity and mortality data might not be not accessible.

The impact of meal timing on performance, sleepiness, gastric upset, and hunger during simulated night shift

This study examined the impact of eating during simulated night shift on performance and subjective complaints. Subjects were randomized to eating at night (n=5; 23.2 ± 5.5 y) or not eating at night (n=5; 26.2 ± 6.4 y). All participants were given one sleep opportunity of 8 h (22:00 h-06:00 h) before transitioning to the night shift protocol. During the four days of simulated night shift participants were awake from 16:00 h-10:00 h with a daytime sleep of 6 h (10:00 h-16:00 h). In the simulated night shift protocol, meals were provided at ≈0700 h, 1900 h and 0130 h (eating at night); or ≈0700 h, 0930 h, 1410 h and 1900 h (not eating at night). Subjects completed sleepiness, hunger and gastric complaint scales, a Digit Symbol Substitution Task and a 10-min Psychomotor Vigilance Task. Increased sleepiness and performance impairment was evident in both conditions at 0400 h (p<0.05). Performance impairment at 0400 h was exacerbated when eating at night. Not eating at night was associated with elevated hunger and a small but significant elevation in stomach upset across the night (p<0.026). Eating at night was associated with elevated bloating on night one, which decreased across the protocol. Restricting food intake may limit performance impairments at night. Dietary recommendations to improve night-shift performance must also consider worker comfort.

Reliability and Validity of the Turkish Version of the Gastrointestinal Symptom Rating Scale

The purpose of this methodological study is to investigate the validity and reliability of the Turkish version of the Gastrointestinal Symptom Rating Scale (GSRS). The scale was adapted to the Turkish language via backward translation. Content validity was examined by referring to experts. Reliability was examined via test-retest reliability and internal consistency, and validity was examined with divergent and convergent validity. The Epworth Sleepiness Scale (ESS) and the Marlowe-Crowne Social Desirability Scale (MCSDS) were used for divergent validity. As for convergent validity, the Constipation Severity Instrument (CSI) and the Patient Assessment of Constipation Quality of Life Scale (PAC-QOLQ) were utilized. The relationship between the GSRS and the health-related quality of life (36-item short-form health survey [SF-36]) was also analyzed. The study population consisted of patients in orthopedic clinic who volunteered to participate. Test-retest reliability was examined with the participation of 30 patients; internal consistency and validity were examined with 150 patients. Test-retest reliability correlation coefficients of the GSRS varied from 0.39 to 0.87 for all items. For internal consistency, the GSRS's item total correlation was found to be 0.17-0.67, and Cronbach α was 0.82 for all items. There was a positive linear significant correlation between the GSRS, CSI, and PAC-QOLQ. There was no significant correlation between the GSRS, MCSDS, and ESS. Higher GSRS scores inversely correlated with general quality of life (SF-36). The Turkish version of the GSRS has been found to be a reliable and valid instrument for assessing patients' gastrointestinal symptoms. Therefore, this instrument can be confidently used with Turkish individuals.

Lifestyle and bowel movements in school children: Results from the Toyama Birth Cohort Study

BACKGROUND

Constipation is a prevalent health disorder. There have been few epidemiological surveys on constipation in Japanese children. The aim of this study was to evaluate the prevalence of non-daily bowel movements (BM) and irregular BM among children and to identify modifiable lifestyle factors relevant to bowel habits.

METHODS

Subjects were from the Toyama Birth Cohort Study in Japan. A total of 7762 children aged 9-10 years were investigated via questionnaire in 1999. We evaluated bowel habit and the relationship between lifestyle and BM. Non-daily BM and totally irregular BM were defined as dependent variables in the present study.

RESULTS

Non-daily BM were reported by 21.8% of boys and by 31.6% of girls, while 10.6% of boys and 18.3% of girls had totally irregular BM. Non-daily BM were significantly associated with skipping breakfast (OR, 1.23), slow eating (OR, 1.13), physical inactivity (OR, 1.50) and late wake up (OR, 1.29). Totally irregular BM were significantly correlated with skipping breakfast (OR, 1.30), slow eating (OR, 1.41), physical inactivity (OR, 1.27), long TV viewing (OR, 1.52), late bedtime (OR, 1.43), and short sleep duration (OR, 1.33). More girls had non-daily and totally irregular BM than boys, and these sex differences were not reduced after adjusting for lifestyle variables.

CONCLUSIONS

Non-daily and totally irregular BM are common in children, and there are many relevant lifestyle factors. Establishing regular lifestyle habits may lessen constipation.

The Circadian Clock Gene BMAL1 Coordinates Intestinal Regeneration

BACKGROUND & AIMS

The gastrointestinal syndrome is an illness of the intestine caused by high levels of radiation. It is characterized by extensive loss of epithelial tissue integrity, which initiates a regenerative response by intestinal stem and precursor cells. The intestine has 24-hour rhythms in many physiological functions that are believed to be outputs of the circadian clock: a molecular system that produces 24-hour rhythms in transcription/translation. Certain gastrointestinal illnesses are worsened when the circadian rhythms are disrupted, but the role of the circadian clock in gastrointestinal regeneration has not been studied.

METHODS

We tested the timing of regeneration in the mouse intestine during the gastrointestinal syndrome. The role of the circadian clock was tested genetically using the BMAL1 loss of function mouse mutant in vivo, and in vitro using intestinal organoid culture.

RESULTS

The proliferation of the intestinal epithelium follows a 24-hour rhythm during the gastrointestinal syndrome. The circadian clock runs in the intestinal epithelium during this pathologic state, and the loss of the core clock gene, BMAL1, disrupts both the circadian clock and rhythmic proliferation. Circadian activity in the intestine involves a rhythmic production of inflammatory cytokines and subsequent rhythmic activation of the JNK stress response pathway.

CONCLUSIONS

Our results show that a circadian rhythm in inflammation and regeneration occurs during the gastrointestinal syndrome. The study and treatment of radiation-induced illnesses, and other gastrointestinal illnesses, should consider 24-hour timing in physiology and pathology.

Negative impacts of shiftwork and long work hours

PURPOSE

Healthcare organizations often have to provide patient care around the clock. Shift work (any shift outside of 7 a.m. to 6 p.m) and long work hours increase the risk for short sleep duration and sleep disturbances. Thirty-two percent of healthcare workers report they do not get enough sleep. The purpose of the article is to give an overview of the wide range of risks to nurses, patients, and employers that are linked to shift work, long work hours, and poor sleep from other sources.

FINDINGS

Shift work and long work hours increase the risk for reduced performance on the job, obesity, injuries, and a wide range of chronic diseases. In addition, fatigue-related errors could harm patients. Fatigued nurses also endanger others during their commute to and from work.

CONCLUSION AND CLINICAL RELEVANCE

The key strategy to reduce these risks is making sleep a priority in the employer's systems for organizing work and in the nurse's personal life.

The role of the circadian system in fractal neurophysiological control

Many neurophysiological variables such as heart rate, motor activity, and neural activity are known to exhibit intrinsic fractal fluctuations - similar temporal fluctuation patterns at different time scales. These fractal patterns contain information about health, as many pathological conditions are accompanied by their alteration or absence. In physical systems, such fluctuations are characteristic of critical states on the border between randomness and order, frequently arising from nonlinear feedback interactions between mechanisms operating on multiple scales. Thus, the existence of fractal fluctuations in physiology challenges traditional conceptions of health and disease, suggesting that high levels of integrity and adaptability are marked by complex variability, not constancy, and are properties of a neurophysiological network, not individual components. Despite the subject's theoretical and clinical interest, the neurophysiological mechanisms underlying fractal regulation remain largely unknown. The recent discovery that the circadian pacemaker (suprachiasmatic nucleus) plays a crucial role in generating fractal patterns in motor activity and heart rate sheds an entirely new light on both fractal control networks and the function of this master circadian clock, and builds a bridge between the fields of circadian biology and fractal physiology. In this review, we sketch the emerging picture of the developing interdisciplinary field of fractal neurophysiology by examining the circadian system's role in fractal regulation.

Impact of shiftwork on irritable bowel syndrome and functional dyspepsia

Disturbances in biological rhythms could lead to unfavorable health impact. This study aimed to evaluate the prevalence of functional dyspepsia (FD) and irritable bowel syndrome (IBS) in rotating shift workers, and to determine the factors that have significant association with the prevalence of FD and IBS. The research had been carried out among nurses and nursing assistants working at Ewha Womans University Mokdong Hospital between December 2010 and February 2011. The subjects completed self-reported questionnaires, including the quality of the sleep and the level of stress. The prevalence of FD and IBS defined by ROME III criteria, and factors associated the disorders in rotating shift workers were compared with those of day workers. A total of 207 subjects were included in the study with 147 rotating shift workers (71.0%), and 60 (29.0%) day workers. The prevalence of IBS in rotating shift workers was higher than that in day workers (32.7% vs 16.7%, P = 0.026). However, no significant difference in the prevalence of FD was observed between the two groups (19.7% vs 20.0%, P = 0.964). In the multivariate analysis, the risk factors for IBS were rotating shift work (OR, 2.36; 95% CI, 1.01-5.47) and poor sleep quality (OR, 4.13; 95% CI, 1.82-9.40), and the risk factors for FD were poor sleep quality (OR, 2.31; 95% CI, 1.01-5.28), and severe stress (OR, 2.19; 95% CI, 1.06-4.76). A higher prevalence of IBS among rotating shift workers could be directly associated with the circadian rhythm disturbance. The circadian rhythm disturbance may be related with the pathogenesis of IBS.

Seasonal patterns of abdominal pain consultations among adults and children

BACKGROUND AND AIM

Consultations for chronic abdominal pain are frequent in adults and children. A seasonal pattern of abdominal pain consultations with winter predominance was shown in previous pediatric studies; however, no studies have investigated whether such a pattern exists in adult patients. Understanding the differences in seasonal patterns of abdominal pain consultations among adults and children may indicate that either different mechanisms exist for common chronic pain conditions or triggering factors may vary by age. The aim of the study was to investigate whether a seasonal variation in abdominal pain consultation patterns exists among adults and children.

METHODS

The number of outpatient consultations among children (5-17 years) and adults (18 years or older) with a diagnosis of abdominal pain of nonspecified origin (International Classification of Diseases-9 code 789.0) from May 2000 to December 2008 was identified in an administrative claims database. The primary outcome measure was the rate of abdominal pain consultations (total number of abdominal pain consultations/total number of distinct patients by month×1000) by season in children and adults. Seasons were defined as follows: winter (December-February), spring (March-May), summer (June-August), and fall (September-November). A trend test was conducted to determine the degree of linearity in the patterns between the 2 groups. Among children, subanalyses by age 5 to 11 years and 12 to 17 years and sex were conducted.

RESULTS

A total of 172.4 million distinct patients (13.4% children, 87.6% adults) were identified in the database between May 2000 and December 2008. During the same time period, 15.6 million patient consultations for abdominal pain were identified (10.1% children, 89.9% adults). Children demonstrated a seasonal pattern in abdominal pain consultations, which best fit a quadratic regression curve, with consultations less common during the summer months. Abdominal pain consultations in adults were linear with no seasonal predominance. The trend in seasonal variation of abdominal pain consultations among children stratified by age and sex remained consistent with the overall child population.

CONCLUSIONS

Abdominal pain consultations in children are less common during summer months, whereas no evidence of seasonal pattern of consultation was found in adults. Factors involved in the pathogenesis of abdominal pain in adults and children may differ.

Sleep disruption secondary to overnight call shifts is associated with irritable bowel syndrome in residents: a cross-sectional study

OBJECTIVES

Sleep disruption has been associated with irritable bowel syndrome (IBS). We hypothesized that residents with greater sleep disruption secondary to intermittent overnight call shifts would have a higher prevalence of IBS.

METHODS

Postgraduate residents completed a Web-based survey including demographic data, frequency and characteristics of call shifts, the Rome III questionnaire, and the IBS-quality of life measure.

RESULTS

For every hour of sleep deprivation while on call vs. off call, the odds ratio for an increased likelihood of IBS was 1.32, after adjustment for age and gender. The mean number of calls per block, sleep deprivation while on call, and specialty program vs. family practice each predicted the severity of IBS.

CONCLUSIONS

Sleep disruption secondary to overnight call in residents was associated with an increased prevalence of IBS.

A cross-sectional study of the association between overnight call and irritable bowel syndrome in medical students

BACKGROUND

Shift work has been associated with irritable bowel syndrome (IBS), which includes gastrointestinal symptoms such as abdominal pain, constipation and diarrhea. Overnight call shifts also lead to a disruption of the endogenous circadian rhythm.

HYPOTHESIS

Medical students who perform intermittent overnight call shifts will demonstrate a higher prevalence of IBS symptoms when compared with medical students who perform no overnight call shifts.

METHODS

First- and second-year (preclinical) medical students have no overnight call requirements, whereas third- and fourth-year medical (clerkship) students do have overnight call requirements. All medical students at the Schulich School of Medicine and Dentistry (London, Ontario) were invited to complete an anonymous, web-based survey or an identical paper copy that included demographic data, the Rome III questionnaire and the IBS-Quality of Life measure (IBS-QOL). The prevalence of IBS symptoms and quality of life secondary to those symptoms were determined.

RESULTS

Data were available for 247 medical students (110 preclinical students, 118 clerkship students and 19 excluded surveys). There was no significant difference in the presence of IBS between preclinical and clerkship students (21 of 110 [19.1%] versus 26 of 118 [22.0%]; P=0.58). The were no significant differences in mean (± SD) IBS-QOL score of those with IBS between preclinical (43.5±8.3) and clerkship students (45.7±13.8) (P=0.53).

CONCLUSIONS

Participation in overnight call was not associated with the development of IBS or a lower quality of life secondary to IBS in medical students.

Interaction of occupational and personal risk factors in workforce health and safety

Most diseases, injuries, and other health conditions experienced by working people are multifactorial, especially as the workforce ages. Evidence supporting the role of work and personal risk factors in the health of working people is frequently underused in developing interventions. Achieving a longer, healthy working life requires a comprehensive preventive approach. To help develop such an approach, we evaluated the influence of both occupational and personal risk factors on workforce health. We present 32 examples illustrating 4 combinatorial models of occupational hazards and personal risk factors (genetics, age, gender, chronic disease, obesity, smoking, alcohol use, prescription drug use). Models that address occupational and personal risk factors and their interactions can improve our understanding of health hazards and guide research and interventions.

Shiftwork Problems

U radu se raspravlja o negativnim utjecajima smjenskog rada koji su klasificirani u četiri kategorije učinaka: na biološke funkcije, radnu efikasnost, društvene / obiteljske aspekte života te na zdravlje. Dan je sustavni pregled dosadašnjih istraživanja zdravstvenih problema smjenskih radnika u čijoj je osnovi narušavanje cirkadijurnih ritmova organizma koju nameće smjenski / noćni rad. Zdravstveni problemi koji se dovode u vezu sa smjenskim radom su ovi: problemi sa spavanjem, gastrointestinalne i kardiovaskularne bolesti, karcinom, problemi s reproduktivnim funkcijama žena te lošije psihičko zdravlje.

U radu se također raspravlja o toleranciji smjenskog rada. Pri tome je kao teoretski okvir povezanosti smjenskog rada i negativnih zdravstvenih posljedica rabljen procesni model koji su postavili Smith i suradnici 1999. Poseban naglasak stavljen je na individualne i organizacijske faktore o kojima ovisi mogućnost prilagodbe na smjenski rad te tolerancija takvog rada. Značajni prediktori tolerancije smjenskog rada su: dob, spol, jutarnjost-večernjost, rigidnost-fleksibilnost u navikama spavanja, obiteljska situacija, higijena spavanja te zdrava prehrana. S obzirom na rezultate istraživanja koji upućuju na povezanost nekih karakteristika organizacije smjenskog rada s tolerancijom prema smjenskom radu, kao što su: broj radnih smjena i trajanje smjene, broj sukcesivnih noćnih smjena, regularnost smjena, brzina i smjer rotacije smjena, preporučene su intervencijske strategije u organizaciji smjenskog rada.

Gastrointestinal complaints in shift-working and day-working nurses in Iran

Background

There is evidence in the scientific literature of the adverse physiological and psychological effects of shift work. The work of nurses in hospitals is connected with shift and night work. Several publications have described gastrointestinal disturbances in shift workers. The aim of this study was to compare the frequency of gastrointestinal (GI) complaints of nurses on a rotating shift with that of nurses on a regular day shift.

Methods

The study involved 160 nurses (133 working in shifts and at night and 27 working on day shifts) in the Shahid Beheshti Hospital in Kashan, Iran. These nurses answered a Gastrointestinal Symptom Questionnaire regarding the presence of gastrointestinal symptoms (including heartburn, regurgitation, constipation, diarrhea and bloating). Positive responses required frequent symptom occurrence in the past 4 weeks. Significance of group differences was assessed by chi-square and Fisher-exact tests.

Results

Prevalence of GI symptoms was significantly higher (p = 0.009) in rotating-shift nurses (81.9%) than in day-shift nurses (59.2%). Irregular meal consumption (p = 0.01) and GI medications (p = 0.002) were all significantly higher among the rotating shift nurses. In both groups, regurgitation was the most common symptom.

Conclusion

Nurses on rotating shifts in Iran experience more GI disturbances than do nurses on day shifts.

Role of clock genes in gastrointestinal motility

Biological rhythms coordinate the timing of our internal bodily functions. Colonic motility follows a rhythm as well: most people will have a bowel movement in the morning and rarely during the night. Recent work provides a potential mechanism for this observation: the mouse colon possesses a functional circadian clock as well as a subset of rhythmically expressed genes that may directly impact on colonic motility. Furthermore, measures of colonic motility such as the colonic tissue contractile response to acetylcholine, stool output, and intracolonic pressure changes vary as a function of the time of day, but these variations are attenuated in mice with disrupted clock function. These laboratory findings are supported by clinical observations. Gastrointestinal symptoms such as diarrhea or constipation are prevalent among shift workers and time-zone travelers, both of which are conditions associated with disruptions in biological rhythms. This review will discuss new insights into the role of clock genes in colonic motility and their potential clinical relevance.

The impact of rotating shift work on the prevalence of irritable bowel syndrome in nurses

OBJECTIVES

Shift work has been associated with gastrointestinal symptoms such as abdominal pain, constipation, and diarrhea. These symptoms overlap with those reported by patients with functional bowel disorders. Because shift work will lead to misalignment between the endogenous circadian timing system and the external 24 h environment, we hypothesized that nurses participating in shift work will have a higher prevalence of functional bowel disorders when compared with nurses participating in day shifts.

METHODS

Nurses engaged in patient care were invited to complete Rome III, irritable bowel syndrome-quality of life measure (IBS-QOL) and modified Sleep-50 questionnaires. Respondents were classified as working day, night, or rotating shifts. The prevalence of IBS, functional constipation, functional diarrhea, and individual gastrointestinal symptoms was determined.

RESULTS

Data were available for 399 nurses (214 day shift, 110 night shift, and 75 rotating shift workers). Rotating shift nurses had a significantly higher prevalence of IBS compared to day shift nurses (48% vs. 31%, P<0.01). Multivariable logistic regression correcting for age, gender, and sleep quality proved this association robust. IBS-QOL scores among groups were similar. Prevalence of functional constipation and functional diarrhea was similar between groups. Rotating shift nurses had a significantly higher prevalence of abdominal pain compared to day shift (81% vs. 54%, P<0.0001) and night shift workers (61%, P=0.003).

CONCLUSIONS

Participation in shift work, especially rotating shift work, is associated with the development of IBS and abdominal pain that is independent of sleep quality. Circadian rhythm disturbances may have a function in the pathogenesis of IBS and abdominal pain.

Rhythmic changes in colonic motility are regulated by period genes

Human bowel movements usually occur during the day and seldom during the night, suggesting a role for a biological clock in the regulation of colonic motility. Research has unveiled molecular and physiological mechanisms for biological clock function in the brain; less is known about peripheral rhythmicity. This study aimed to determine whether clock genes such as period 1 (per1) and period2 (per2) modulate rhythmic changes in colonic motility. Organ bath studies, intracolonic pressure measurements, and stool studies were used to examine measures of colonic motility in wild-type and per1per2 double-knockout mice. To further examine the mechanism underlying rhythmic changes in circular muscle contractility, additional studies were completed in neuronal nitric oxide synthase (nNOS) knockout mice. Intracolonic pressure changes and stool output in vivo, and colonic circular muscle contractility ex vivo, are rhythmic with greatest activity at the start of night in nocturnal wild-type mice. In contrast, rhythmicity in these measures was absent in per1per2 double-knockout mice. Rhythmicity was also abolished in colonic circular muscle contractility of wild-type mice in the presence of N(omega)-nitro-L-arginine methyl ester and in nNOS knockout mice. These findings suggest that rhythms in colonic motility are regulated by both clock genes and a nNOS-mediated inhibitory process and suggest a connection between these two mechanisms.

Role of biological rhythms in gastrointestinal health and disease

The molecular basis for biological rhythms is formed by clock genes. Clock genes are functional in the liver, within gastrointestinal epithelial cells and neurons of the enteric nervous system. These observations suggest a possible role for clock genes in various circadian functions of the liver and the gastrointestinal tract through the modulation of organ specific clock-controlled genes. Consequently, disruptions in circadian rhythmicity may lead to adverse health consequences. This review will focus on the current understanding of the role of circadian rhythms in the pathogenesis of gastrointestinal- and hepatic disease such as obesity, non-alcoholic fatty liver disease, alcoholic fatty liver disease and alterations in colonic motility.

Restless Legs Syndrome in shift workers: A cross sectional study on male assembly workers

Background

Restless Legs Syndrome (RLS) is a common neurological movement disorder characterized by symptoms that follow a circadian pattern. Night and rotating shift work schedules exert adverse effects on functions of the human body by disturbing circadian rhythms, and they are known to cause sleep disturbances and insomnia. In this paper, we investigate the possible association between shift work and RLS.

Methods

This cross sectional study was conducted in an automobile manufacturing factory in Tehran, Iran. A total of 780 male assembly workers were recruited in three groups, each with 260 workers: workers on a permanent morning shift (A) and two different rotating shift schedules (B and C) with morning, afternoon and night shifts. We used the international RLS study group criteria for diagnosis of RLS, and the severity scale for severity assessment in subjects with RLS. Self administered questionnaires were used to gather information on age, smoking, work history, medical condition, and existence and severity of RLS symptoms.

Results

The prevalence of RLS was significantly higher in rotational shift workers (15%) than workers with permanent morning work schedule (8.5%). In workers suffering from RLS, we found greater mean values of age and work experience, higher percentages of drug consumption, smoking, and co-morbid illnesses compared with subjects who did not have RLS, although these differences were statistically significant only for age, work experience and drug consumption.

Conclusion

Rotational shift work acts as a risk or exacerbating factor for Restless Legs Syndrome.

A review of work schedule issues and musculoskeletal disorders with an emphasis on the healthcare sector

Musculoskeletal disorders (MSDs) are a significant cause of morbidity in healthcare workers. The influence of shift work and long work hours on risk for MSDs is an area that needs further exploration. The purpose of this report is to assess research progress and gaps across studies that examined the relationship between demanding work schedules and MSD outcomes. A literature search identified 23 peer-reviewed publications in the English language that examined MSDs and long work hours, shift work, extended work shifts, mandatory overtime, or weekend work. Eight studies that examined long work hours and had some controls for physical job demands reported a significant increase in one or more measures of MSDs. Fourteen studies examining shift work had incomparable methods and types of shift work, and therefore, no clear trends in findings were identified. A small number of studies examined mandatory overtime, work on weekends and days off, and less than 10 h off between shifts. Given the complexity of the work schedule research topic, relatively few studies have adequately examined the relationship of work schedules and musculoskeletal outcomes. The review discusses research gaps including methodological issues and suggests research priorities.

Transcriptional profiling of mRNA expression in the mouse distal colon

BACKGROUND & AIMS

Intestinal epithelial cells and the myenteric plexus of the mouse gastrointestinal tract contain a circadian clock-based intrinsic time-keeping system. Because disruption of the biological clock has been associated with increased susceptibility to colon cancer and gastrointestinal symptoms, we aimed to identify rhythmically expressed genes in the mouse distal colon.

METHODS

Microarray analysis was used to identify genes that were rhythmically expressed over a 24-hour light/dark cycle. The transcripts were then classified according to expression pattern, function, and association with physiologic and pathophysiologic processes of the colon.

RESULTS

A circadian gene expression pattern was detected in approximately 3.7% of distal colonic genes. A large percentage of these genes were involved in cell signaling, differentiation, and proliferation and cell death. Of all the rhythmically expressed genes in the mouse colon, approximately 7% (64/906) have been associated with colorectal cancer formation (eg, B-cell leukemia/lymphoma-2 [Bcl2]) and 1.8% (18/906) with various colonic functions such as motility and secretion (eg, vasoactive intestinal polypeptide, cystic fibrosis transmembrane conductance regulator).

CONCLUSIONS

A subset of genes in the murine colon follows a rhythmic expression pattern. These findings may have significant implications for colonic physiology and pathophysiology.

Shift-work and suicide ideation among police officers

BACKGROUND

This cross-sectional study assessed the association of shift work with suicide ideation among police officers.

METHODS

Shift work was based on daily payroll records over 5 years (41 women, 70 men). Standardized psychological measures were employed. ANOVA and Poisson regression were used to evaluate associations.

RESULTS

Among policewomen with increased depressive symptoms, prevalence of suicide ideation increased by 116% for every 10-unit increase in percentage of hours worked on day shift (prevalence ratio (PR) = 2.16; 95% confidence interval (CI) = 1.22-3.71). Among policemen with higher (but not lower) posttraumatic stress disorder (PTSD) symptoms, prevalence of suicide ideation increased by 13% with every 10-unit increase in the percentage of hours worked on afternoon shift (PR = 1.13; 95% CI = 1.00-1.22).

CONCLUSION

Prevalence of suicide ideation significantly increased among policewomen with higher depressive symptoms and increasing day shift hours, and among policemen with higher PTSD symptoms with increasing afternoon shift hours.

Expression levels of estrogen receptor beta are modulated by components of the molecular clock

Circadian regulation of gene expression plays a major role in health and disease. The precise role of the circadian system remains to be clarified, but it is known that circadian proteins generate physiological rhythms in organisms by regulating clock-controlled target genes. The estrogen receptor beta (ERbeta) is, together with ERalpha, a member of the nuclear receptor superfamily and a key mediator of estrogen action. Interestingly, recent studies show that disturbed circadian rhythmicity in humans can increase the risk of reproductive malfunctions, suggesting a link between the circadian system and ER-mediated transcription pathways. Here, we identify a novel level of regulation of estrogen signaling where ERbeta, but not ERalpha, is controlled by circadian clock proteins. We show that ERbeta mRNA levels fluctuate in different peripheral tissues following a robust circadian pattern, with a peak at the light-dark transition, which is maintained under free-running conditions. Interestingly, this oscillation is abolished in clock-deficient BMAL1 knockout mice. Circadian control of ERbeta expression is exerted through a conserved E-box element in the ERbeta promoter region that recruits circadian regulatory factors. Furthermore, using small interfering RNA-mediated knockdown assays, we show that the expression levels of the circadian regulatory factors directly influence estrogen signaling by regulating the intracellular levels of endogenous ERbeta.

Medication use in patients with restless legs syndrome compared with a control population

Primary restless legs syndrome (RLS) is a sensorimotor disorder causing chronic sleep deprivation in those with moderate to severe symptoms. It has been associated with other medical conditions, such as high blood pressure, depression and attention deficit hyperactive disorder (ADHD). If these conditions are more prevalent for RLS patients, then it would be expected RLS patients would use relatively more of the medications treating these conditions. Current medication use was obtained from 110 RLS patients and 54 age, race and gender-matched local-community controls. Each subject was diagnosed as primary RLS or having no indications for RLS by a clinician board-certified in sleep medicine. The RLS group used more medications than the control group even when medications used for treating RLS were excluded. Significantly more of the RLS patients than controls used anti-depressants, gastro-intestinal (GI) medications and asthma/allergy medications. RLS patients compared with those without RLS are more likely to use medications not related to treating RLS. Moreover they use medications for conditions that have not previously been considered related to RLS, i.e. GI and asthma/allergy conditions.

Clock gene expression in the murine gastrointestinal tract: endogenous rhythmicity and effects of a feeding regimen

BACKGROUND & AIMS

Based on observations that the gastrointestinal tract is subject to various 24-hour rhythmic processes, it is conceivable that some of these rhythms are under circadian clock gene control. We hypothesized that clock genes are present in the gastrointestinal tract and that they are part of a functional molecular clock that coordinates rhythmic physiologic functions.

METHODS

The effects of timed feeding and vagotomy on temporal clock gene expression (clock, bmal1, per1-3, cry1-2) in the gastrointestinal tract and suprachiasmatic nucleus (bmal, per2) of C57BL/6J mice were examined using real-time polymerase chain reaction and Western blotting (BMAL, PER2). Colonic clock gene localization was examined using immunohistochemistry (BMAL, PER1-2).

RESULTS

Clock immunoreactivity was observed in the myenteric plexus and epithelial crypt cells. Clock genes were expressed rhythmically throughout the gastrointestinal tract. Timed feeding shifted clock gene expression at the RNA and protein level but did not shift clock gene expression in the central clock. Vagotomy did not alter gastric clock gene expression compared with sham-treated controls.

CONCLUSIONS

The murine gastrointestinal tract contains functional clock genes, which are molecular core components of the circadian clock. Daytime feeding in nocturnal rodents is a strong synchronizer of gastrointestinal clock genes. This synchronization occurs independently of the central clock. Gastric clock gene expression is not mediated through the vagal nerve. The presence of clock genes in the myenteric plexus and epithelial cells suggests a role for clock genes in circadian coordination of gastrointestinal functions such as motility, cell proliferation, and migration.

A systematic review of the neurobehavioural and physiological effects of shiftwork systems

Shiftwork is a common experience for many workers. There are a wide range of shift systems in use, with a number of general approaches and myriad variations of each one. Many aspects of shift systems have been studied, but attempts to reach definitive conclusions about appropriate designs have been hampered by a number of methodological issues. The aim of this systematic review was to provide evidence-based recommendations on the effect of various shift systems on neurobehavioural and physiological functioning and to identify areas which are lacking in appropriate evidence. Two main aspects of shift design were able to be considered-the direction of shift rotation and extended shift length (mainly 12-h shifts). Other areas for which there was at least one relevant paper of adequate methodology were the use of naps during night shifts, the starting time of shifts, and several other specific shift issues. Overall, the review found there is insufficient evidence to support definitive conclusions regarding any of these factors. However, the analysis provides support for the use of forward rotating shift systems in preference to backward rotating shift systems, at last as far as 8-h shifts are concerned. There are many unanswered questions in shift design. For these questions to be answered, it is important that the methodological shortcomings present in most of the studies published to date be overcome.

Biologic clocks and the gut

The gastrointestinal tract displays biologic rhythms in basal gastric acid output, epithelial cell proliferation, gastrointestinal motility, and appetite regulation. Furthermore, the development of gastrointestinal complications after administration of aspirin and after chemo- and radiotherapy for metastatic colon cancer depends on the time of administration. Biologic rhythms are driven by so-called clock genes. Thus, it is conceivable that subsets of genes in the gastrointestinal tract are under clock gene control as well. The purpose of this article is to discuss basic concepts in the studies of biologic rhythms, to review examples of biologic rhythms in the gastrointestinal tract, and to discuss examples of gastrointestinal diseases in which alterations in biologic rhythms may play a pathogenetic role.

Impact of Shift Work on the Health and Safety of Nurses and Patients

Shift work generally is defined as work hours that are scheduled outside of daylight. Shift work disrupts the synchronous relationship between the body's internal clock and the environment. The disruption often results in problems such as sleep disturbances, increased accidents and injuries, and social isolation. Physiologic effects include changes in rhythms of core temperature, various hormonal levels, immune functioning, and activity-rest cycles. Adaptation to shift work is promoted by reentrainment of the internally regulated functions and adjustment of activity-rest and social patterns. Nurses working various shifts can improve shift-work tolerance when they understand and adopt counter measures to reduce the feelings of jet lag. By learning how to adjust internal rhythms to the same phase as working time, nurses can improve daytime sleep and family functioning and reduce sleepiness and work-related errors. Modifying external factors such as the direction of the rotation pattern, the number of consecutive night shifts worked, and food and beverage intake patterns can help to reduce the negative health effects of shift work. Nurses can adopt counter measures such as power napping, eliminating overtime on 12-hour shifts, and completing challenging tasks before 4 am to reduce patient care errors.

Global estimates of fatal work-related diseases

BACKGROUND

Work-related mortality is a relatively new concept which aims to widen occupational health and safety; to take into account not only recognized fatal occupational accidents and diseases but also other work-related deaths. Few countries in the world have a register for work-related diseases.

METHODS

Estimates are calculated using baseline world mortality scenarios of all diseases for the year 2000 and attributable fractions made for work-related diseases in Finland, as adjusted.

RESULTS

It is estimated that about 2 million work-related deaths take place annually. Men suffer two thirds of those deaths. The biggest groups of work-related diseases are cancers, circulatory diseases and communicable diseases.

CONCLUSIONS

Information about work-related diseases is needed for prevention, as people in developed countries are working longer, and the age of retirement is being raised in many countries. As a result, workers are being exposed to different kinds of substances and working conditions for a longer time. In developing countries, work exposures may already start in infancy. Due to industrialization, workers in developing countries are facing new conditions with a lack of relevant knowledge and skills. With the help of information, nations can direct resources and skills for appropriate purposes such as regulatory measures on health and safety at work.

Circadian timing in health and disease

Metabolic status varies predictably on a daily and seasonal basis in order to adapt to the cyclical environment. The hypothalamic circadian pacemaker of the suprachiasmatic nuclei (SCN) co-ordinates these metabolic cycles. Circadian timing is based upon a transcriptional/post-translational negative feedback loop involving a series of core clock genes and their products. Local molecular clocks in peripheral tissues are synchronised by a variety of autonomic, paracrine and endocrine cues reflective of SCN time, thereby ensuring internal temporal co-ordination and optimal metabolic function. Disturbances of this co-ordination, as occur in long-term shift work, have a major impact on health.