Metabolic Syndrome in Permanent Night Workers

Night and shift work might be risk factors for metabolic and cardiovascular disorders due to interference with diet, circadian metabolic rhythms, and lifestyle. The relationship between permanent night work and metabolic and cardiovascular risk factors was explored in a retrospective longitudinal study of workers employed in a large municipal enterprise in charge of street cleaning and domestic waste collection. All subjects who had worked night shifts between 1976 and 2007 as hand sweepers, motor sweepers, and delivery tricar drivers were compared with subjects who always worked the same jobs but on day shifts. From the periodical medical surveillance files, we identified 488 male workers who had been examined on average five times (minimum 2, maximum 14) during the study period, for a total of 2,328 medical examinations; 157 always had worked day shifts, 12 always the night shift, and 319 both (initially day and subsequently night shifts). Their age ranged from 22 to 62 yrs, and work experience varied from 1 to 28 yrs. Lifestyle habits (smoking, alcohol consumption), body mass index, serum glucose, total cholesterol, tryglicerides, hepatic enzymes, blood pressure, resting electrocardiogram, diabetes, coronary heart disease, hypertension, and related drugs were taken into consideration for the analysis. We used generalized estimating equations (GEE) models (exchangeable correlation matrix) to analyze the relationship between night work and health effects while accounting for within‐subject correlations and adjusting for study period, job, age, and lifestyle variables. As a whole, night workers smoked more and had significantly higher BMI, serum total cholesterol, and triglycerides than day workers. Both the inter‐individual comparison between day and night workers and the intra‐individual comparison among the workers, who were day workers at the beginning of their employment and later became night workers, showed a significant increase in BMI, total cholesterol, and tryglicerides associated with night work. No consistent effect was seen on fasting glucose, hepatic enzymes, and blood pressure, whereas a higher incidence of coronary heart disease was recorded in night workers.     

Self-Reported Health and Sleep Complaints Among Nursing Personnel Working Under 12 h Night and Day Shifts

This cross-sectional exploratory study involved health care workers of various skill types and levels. We tested the hypothesis that the prevalence of diseases, sleep complaints, and insufficient time for nonprofessional activities (family, leisure, and rest) are higher among night than day workers. Data collection was carried out in two public hospitals using questionnaires and other forms. Night work was explored as a risk factor, considering a night worker as one who had at least one night job on the occasion of the research. Data were assessed by a univariate analysis. The association between work schedule and the dependent variables—health conditions, sleep complaints, and insufficient time for nonprofessional activities—was evaluated through the estimation of the prevalence ratio, with a confidence interval of 95%. Two hundred and fifty-eight female nursing personnel participated; 41.5% were moonlighters, and only 20 worked a shift of less than 12 h in length. Reports of migraine and need of medical care the 2 weeks before the survey were more prevalent among day than night workers (PR = 0.71; CI = 0.55–0.92 and PR = 0.71; CI = 0.52–0.95, respectively). Migraine headaches occurred less frequently among night than day workers as confirmed by comparing the reports of the night workers and day workers whose work history was always day shifts (PR = 0.74; CI = 0.57–0.96). Reports of mild emotional disorders (mild depression, tension, anxiety, or insomnia) were less frequent among night (PR = 0.76; CI = 0.59–0.98) and ex-night workers (PR = 0.68; CI = 0.50–0.91) than day workers who never had worked a night job. The healthy worker effect does not seem to explain the results of the comparisons between day and night workers. The possible role of exposure by day workers to some risk factors, such as stress, was suggested as an explanation for these results. No significant difference was observed between night and day workers as to sleep complaints, a result that may have been influenced by the nature of the shift-work schedule (no successive night shifts) and possibly nap taking during the night shift. Moreover, the long work hours and moonlighting of the healthcare workers, which is common in Brazil, may have masked other possible differences between the day and night workers. Among night workers, a significant relation was found between years working nights (more than 10 yrs) and high cholesterol values (PR = 2.58; CI = 1.07–6.27), a result that deserves additional study. Working nights more than four times per 2-week span was related to complaints about insufficient time for children (PR = 1.96; CI = 1.38–2.78) and rest/leisure (PR = 1.54; CI = 1.20–1.99). These results can be related to the “social value of time,” as evenings and nights are when families usually spend time together. The complexity of the professional life and the consequent heterogeneity of the group of workers under shift-work schemes confound the results. More in-depth study of the questions raised here demands a more sophisticated epidemiological treatment and larger sample size.     

EPIGENETIC EFFECTS OF SHIFTWORK ON BLOOD DNA METHYLATION

In the present study, the authors investigated the effects of shiftwork exposure on DNA methylation using peripheral blood DNA from subjects working in two chemical plants in Northern Italy. The investigation was designed to evaluate (a) DNA methylation changes in Alu and long interspersed nuclear element-1 (LINE-1) repetitive elements as a surrogate of global methylation and (b) promoter methylation of glucocorticoid receptor (GCR), tumor necrosis factor alpha (TNF-α), and interferon-gamma (IFN-γ). One hundred and fifty white male workers (mean?±?SD: 41.0?±?9 yrs of age) were examined: 100 3?×?8 rotating shiftworkers (40.4?±?8.7 yrs of age) and 50 day workers (42.2?±?9.4 yrs of age). The authors used bisulfite-pyrosequencing to estimate repetitive elements and gene-specific methylation. Multiple regression analysis, adjusted for age, body mass index (BMI), and job seniority, did not show any significant association between the five DNA methylation markers and shiftwork. However, job seniority, in all subjects, was significantly associated with Alu (β?=??0.019, p?=?.033) and IFN-γ (β?=??0.224, p?<?.001) methylation, whereas TNF-α methylation was inversely correlated with age (β?=??0.093, p?<?.001). Considering only shiftworkers, multiple regression analysis, adjusted for age, BMI, and job seniority, showed a significant difference between morning and evening types in TNF-α methylation (mean morning type [MT] 11.425 %5mC versus evening type [ET] 12.975 %5mC; β?=?1.33, p?=?.022). No difference was observed between good and poor tolerance to shiftwork. Increasing job seniority (<5, 5–15, >15 yrs) was associated with significantly lower Alu (β?=??0.86, p?=?.006) and IFN-γ methylation (β?=??6.50, p?=?.007) after adjustment for age, BMI, and morningness/eveningness. In addition, GCR significantly increased with length of shiftwork (β?=?3.33, p?=?.05). The data showed alterations in blood DNA methylation in a group of shiftworkers, including changes in Alu repetitive elements methylation and gene-specific methylation of IFN-γ and TNF-α promoters. Further studies are required to determine the role of such alterations in mediating the effects of shiftwork on human health. (Author correspondence: giovanni.costa@unimi.it)     

Morning Melatonin Has Limited Benefit as a Soporific For Daytime Sleep After Night Work

Exogenous melatonin administration in humans is known to exert both chronobiotic (phase shifting) and soporific effects. In a previous study in our lab, young, healthy, subjects worked five consecutive simulated night shifts (23:00 to 07:00 h) and slept during the day (08:30 to 15:30 h). Large phase delays of various magnitudes were produced by the study interventions, which included bright light exposure during the night shifts, as assessed by the dim light melatonin onset (DLMO) before (baseline) and after (final) the five night shifts. Subjects also ingested either 1.8 mg sustained‐release melatonin or placebo before daytime sleep. Although melatonin at this time should delay the circadian clock, this previous study found that it did not increase the magnitude of phase delays. To determine whether melatonin had a soporific effect, we controlled the various magnitudes of phase delay produced by the other study interventions. Melatonin (n=18) and placebo (n=18) groups were formed by matching a melatonin participant with a placebo participant that had a similar baseline and final DLMO (±1 h). Sleep log measurements of total sleep time (TST) and actigraphic measurements of sleep latency, TST, and three movement indices for the two groups were examined. Although melatonin was associated with small improvements in sleep quality and quantity, the differences were not statistically significant by analysis of variance. However, binomial analysis indicated that melatonin participants were more likely to sleep better than their placebo counterparts on some days with some measures. It was concluded that, the soporific effect of melatonin is small when administered prior to 7 h daytime sleep periods following night shift work.     

贵州草海保护区钳嘴鹳种群动态

新分布种对当地生态系统的影响具有不确定性,掌握其种群动态对于制定相应的管理策略具有重要意义。钳嘴鹳(Anastomus oscitans)为我国新分布种,目前已扩散至云南、贵州、广西、四川等省(自治区),但对其种群数量及变化规律尚缺乏了解。2013年1月至2014年12月,采用夜栖地直接计数法对贵州省草海自然保护区钳嘴鹳的种群数量进行了监测。结果表明,1)钳嘴鹳主要在夏季出现,冬季数量较少,表现出明显的季节性差异(P0.001)。2)钳嘴鹳种群数量呈现逐年增加趋势,2013年的度夏期(5~10月份)平均数量为200.6只(SD=94.6,n=24),最高数量为427只;2014年的度夏期平均数量增长到356.0只(SD=180.3,n=25),最高数量为602只。3)钳嘴鹳为树上夜栖物种,调查中共发现5处夜栖地,其中位于保护区东南部的簸箕湾是主要夜栖地,在2013、2014年的统计中,该地钳嘴鹳分别占总数量的56.46%和63.53%。由于钳嘴鹳的游荡性较强,建议在其主要分布区开展同步监测,从而整体掌握其种群变化和分布情况。     

Night work,light exposure and melatonin on work days and days off

We aimed to examine the effects of night work on salivary melatonin concentration during and subsequent to night work and the mediating role of light. We included 254 day workers and 87 night workers who were followed during 322 work days and 301 days off work. Each day was defined as the 24 hour period starting from the beginning of a night shift or from waking in the mornings with day work and days off. Light levels were recorded and synchronized with diary information (start and end of sleep and work). On average, participants provided four saliva samples per day, and these were analyzed for melatonin concentration by liquid chromatography tandem mass spectrometry (LC-MS/MS). Differences between day and night workers on work days and days off were assessed with multilevel regression models with melatonin concentration as the primary outcome. All models were stratified or adjusted by time of day. For light exposure, we estimated the total, direct and indirect effects of night work on melatonin concentrations obtaining 95% confidence intervals through bootstrapping. On work days, night workers showed 15% lower salivary melatonin concentrations compared with day workers (?15.0%; 95% CI: ?31.4%; 5.2%). During the night, light exposure mediated a melatonin suppression of approximately 6% (?5.9%, 95% CI: ?10.2%; ?1.5%). No mediating effect of light was seen during the day time. On days off, we observed no difference in melatonin concentrations between day and night workers. These findings are in accordance with a transient and partly light-mediated effect of night work on melatonin production.     

太湖湿地生态系统有机氯污染的夜鹭生物指示

1999年春季,在对无锡鼋头渚鹭鸟种群野外生态调查的基础上,对夜鹭幼鸟反吐物,觅食地底泥和水体进行了采样,并在实验室用气相色谱测定了样品中的α-HCH、β-HCH、γ-HCH、艾氏剂、狄氏剂、异狄氏剂、七氯、环氧七氯、p,p'-DDE、p,p'-DDD、o,p'-DDT和p,p'-DDT等有机氯农药的残留状况,结果表明,在有机氯农药禁用近20年后,六六六的异构体和滴滴涕及其衍生物均能在环境中和夜鹭食物中有不明,在有机氯农药禁用近20年后,六六六的异构体和滴滴涕及其衍生物均能在环境中和夜鹭食物中有不明,在有机氯农药禁用近20年后,六六六的异构体和滴滴涕及其衍生物均能在环境中和夜鹭食物中有不检出,有机氯污染物沿夜鹭食物链产生逐级富集,太湖湿地生态系统中夜鹭卵富集了滴滴涕万倍以上,富集了六六六数千倍,从而使有机氯污染物易被检测,因此夜鹭锘放可作为湿地生态系统有机氯污染的生物指示物。     

紫蓬山区三种鹭种群繁殖成效的研究

：作者１９９６年４～７月在紫蓬山区国家级森林公园,对白鹭、池鹭和夜鹭繁殖种群的数量和繁殖成效进行了研究。结果表明：三块样地中,夜鹭的种群平均密度最大,白鹭的种群平均密度最小;白鹭、池鹭和夜鹭的种群繁殖生产力分别为２３７４ｉｎｄ／ｈｍ２、１４４１ｉｎｄ／ｈｍ２和２０１２ｉｎｄ／ｈｍ２;繁殖成效分别为５２０％、５５１％和４５１％。繁殖成效与巢位高度有关,低位巢卵损失率高,高位巢雏丢失率高。     

Train drivers' sleep quality and quantity during extended relay operations

Relay operations are an important mode of freight transportation within Australia. Relay work requires multiple crews to drive the train continuously from one specified destination to another and return. Importantly, the nature of relay work requires train drivers to sleep on-board during designated resting shifts. The main aim of the present study was to investigate the quality and quantity of sleep obtained in on-board rest facilities (relay vans) during extended (four-day) relay operations. Drivers (n=9) working the Port Augusta to Darwin relay operation volunteered to participate. The first leg of the trip typically took 40 h followed by an overnight stay in Darwin (between 8-12 h) prior to return. Two crews, each consisting of two drivers, changed every 8 h, giving the crew an 8 h rest in the relay van prior to each 8 h working shift. Using polysomnography, home sleep data were collected prior to and following each trip using a standard five-channel EEG montage. All sleep periods during the relay trip (including Darwin) were also recorded. Additionally, subjective sleep quality ratings were recorded following each sleep period. Analyses revealed that the quantity of sleep obtained in the relay vans (3.3 h) was significantly reduced compared to home (6.8 h). In general, the total sleep time was increased at night and reduced during the day. In terms of quality, sleep onset latency, sleep efficiency, and amount of slow wave and rapid eye movement sleep did not differ significantly between home and the relay vans. The results of the study highlight sleep quantity as the main concern during extended relay operations. Future research should focus on investigating the subjective and objective impact of this sleep reduction on waking functions.     

笼养海南(开鸟)的活动时间分配

2003年10月至2004年4月,在对海南[开鸟]进行驯养的基础上,采用全部事件取样法研究了笼养海南[开鸟]的活动时间分配。结果表明：笼养海南[开鸟]一天中除静栖和静立外,其余各行为所占时间比例在白天极少,而在晨（5：00～7：00am）、昏（19：00～21：00pm）和午夜（23：00～1：00am）较大,呈明显的日活动节律;节律变化与季节有关;海南[开鸟]各种行为活动所占比例依次为静栖82．48％、静立8．64％、运动5．36％、取食1．97％、身体护理1．30％、其它0．25％。其时间分配不受季节（春、秋、冬季）影响。