A Prospective Study of Seasonal Variation in Shift‐Work Tolerance

Seasonal effects on shift‐work tolerance were assessed using the Standardized Shiftwork Index and the 21‐item Hamilton Depression Scale. Participants (N=88) mainly worked a two‐day, two‐night, four‐off rotation with 12 h shifts changing at 06∶00 and 18∶00 h in Vancouver, Canada. At this latitude (～49° N), daylength varies seasonally from ～16 to ～8 h, and both daily commutes occur in the dark in mid‐winter and in sunlight in mid‐summer. Questionnaires were completed twice, near the summer and winter solstices (order counterbalanced). Outcome variables were mood, general psychological health, sleep quality, chronic fatigue, physical health, job satisfaction, and social and domestic disruption. Of these, general psychological health and mood were significantly worse in winter, while sleep was more disturbed in summer. In winter, 31% exceeded the cutoff for psychological distress, and >70% scored in the higher than normal range for depressive symptoms. In summer, the proportions dropped to 19% and 53%, respectively. Measures of physical health and psychosocial well‐being showed no seasonal effects. Relationships among explanatory and outcome variables, assessed by linear regression and canonical correlations, were also stable across season. Neuroticism was the strongest predictor of tolerance to shift work. Age was predictive only of sleep disturbance in both summer and winter. These results indicate that time of year can affect important outcome measures in shift‐work assessment and intervention studies. The high average scores on measures of psychological distress and depression in winter suggest that at northern latitudes, some shift schedules may increase the risk of seasonal‐type depression.     

Cognitive functioning of female nurses during the night shift: The impact of age,clock time,time awake and subjective sleepiness

ABSTRACT

Decline in cognitive functioning in the workplace is a major concern for health care systems. Understanding factors associated with nighttime functioning is imperative for instituting organizational risk management policies and developing personalized countermeasures. The present study aims to identify individual factors associated with cognitive functioning during the night shift of hospital nurses working on irregular rotating-shift schedules. Ninety-two female nurses were recruited from 17 wards in two general hospitals, using convenience sampling by clusters. Inclusion criteria were working at least 28 h a week (75% of full time) and one night shift per week. Exclusion criteria were pregnancy, diagnosed sleep disorders or medical conditions that may affect sleep and/or function. Cognitive performance was measured during the middle (03:00 h) and at the end (07:00 h) of the night shift using the Digit Symbol Substitution Task (DSST) and the Letter Cancellation Task (LCT) over two night shifts. Subjective sleepiness was assessed by the Karolinska Sleepiness Scale (KSS) at the same time points. All participants completed a sociodemographic questionnaire, the Munich ChronoType Questionnaire for Shift-Workers (MCTQShift) and the Pittsburgh Sleep Quality Index (PSQI). Sleep duration 24 h before the night shift and time awake since last sleep opportunity were monitored by actigraphy. Univariate repeated measures ANOVA found main effects for clock time (p<0.001), age (p<0.05), time awake (p<0.05) and sleepiness (p<0.01) for DSST correct responses; main effects for clock time (p<0.001) and sleepiness (p<0.001) for LCT capacity; and main effects for clock time (p<0.001) and age (p<0.01) for LCT omission errors. All factors remained significant in a mixed-model analysis for DSST. Cognitive performance among hospital nurses is low during the middle of the night shift and increases at the end of the shift; decreased functioning is associated with increased subjective sleepiness, older age and prolonged time awake. Identifying factors contributing to performance during the night shift may provide a basis for the development of risk management policies and preventative interventions.     

The effect of rising obesity on eligibility to serve in the U.S. public health service commissioned corps

This study investigates how rising obesity has affected eligibility to serve in the United States Public Health Service Commissioned Corps (PHSCC), the uniformed service charged with protecting and promoting public health in the U.S. Data are drawn from the National Health and Nutrition Examination Surveys. Between 1959 and 2010, the percentage of eligible civilians who exceed the weight-for-height and body fat standards of the PHSCC rose from 9.05% to 18.24% among men, and from 6.13% to 23.10% among women. Simulations indicate that a further 1% increase in population body weight will result in an additional 3.42% of men and 5.08% of women exceeding PHSCC accession standards.This study documents an under appreciated consequence of the rise in obesity: fewer Americans eligible to develop and implement a public health response to obesity through the PHSCC. This illustrates how a public health problem can undermine the public health labor force, compromising a response and risking a self-reinforcing trend. These findings are timely as the Patient Protection and Affordable Care Act (ACA) calls for a major expansion of the PHSCC.     

我国煤矿矿山医疗救护工作的SWOT分析

运用SWOT方法分析了目前我国矿山医疗救护工作的整体优势,认识到当前矿山医疗救护工作创新能力不足是面临的主要劣势,剖析了创新发展的机遇和一些结构性威胁,并提出了相应的发展策略。     

Coenzyme B12-dependent diol dehydrase: purification, subunit heterogeneity, and reversible association.

A purification procedure for diol dehydrase (dl-1,2-propanediol hydro-lyase, EC 4.2.1.28) of Klebsiella pneumoniae (Aerobacter aerogenes) ATCC 8724 has been developed which gives the highest specific activity for this enzyme obtained so far. The purified enzyme is homogeneous by the criteria of ultracentrifugation (s_20,w = 8.9 S) and disc gel electrophoresis in the presence of substrate. The molecular weight of approximately 230,000 was obtained by gel filtration and ultracentrifugal sedimentation equilibrium. The enzyme is composed of components F and S whose molecular weights were determined to be approximately 26,000 and 200,000, respectively, by gel filtration. The incubation of both components F and S with the substrate leads to complete reassociation of the components. Disc gel electrophoresis in the presence of sodium dodecyl sulfate and terminal amino acid analyses indicate that component S consists of at least four nonidentical subunits. The reversible association and heterogeneity of the subunits were also demonstrated with the crude enzyme by immunoelectrophoresis.     

Induction of amphibian oocyte maturation by polyvalent cations and alkaline pH in the absence of potassium ions.

The maturation of Xenopus laevis oocytes was studied in media free of added potassium salts. Under these conditions maturation could be triggered by 1 mM Mn²⁺ and La³⁺ and, to a lesser extent, by 2–4 mM Ca²⁺ and Mg²⁺. Maturation induced by 1.5 mM Mn²⁺ was inhibited by K⁺ concentrations above 0.25 mM. Potassium was inhibitory when added up to 2 hr before germinal vesicle breakdown occurred. In potassium-free media, maturation could be induced by incubation of oocytes under mild alkaline media (pH 8.5–9). A high percentage of medium-sized oocytes (stage IV according to Dumont) was induced to mature by progesterone in the absence of potassium. Maturation of oocytes in potassium-free media was normal by the criteria of germinal vesicle breakdown, production of maturation promoting factor, vitelline membrane activation, and inhibition by known maturation inhibitors.     

Validity of the work–energy theorem in molecular dynamics simulations for nanodroplets collisions

Work–energy theorem is examined for nanodroplets collisions in molecular dynamics simulations. Work term and energy term in the work–energy theorem are separately calculated and the equality between them is checked. The terms are based on different microscopic variables. A serious mismatch between them is observed. Therefore, we have to pay attention to calculating some physical quantities related to the work–energy theorem, in particular, for the non-equilibrium properties of nanosystems. This seems to be due to cut-off radius of the potential and a subtraction of two large quantities that are nearly the same. Furthermore, Hurst exponents H are calculated to characterise the time series of the powers for the work term and they change significantly with samplings of the corresponding time series for the case of mismatch.     

FAILURE OF EXTRAOCULAR LIGHT TO FACILITATE CIRCADIAN RHYTHM REENTRAINMENT IN HUMANS

Although extraocular light can entrain the circadian rhythms of invertebrates and nonmammalian vertebrates, almost all studies show that the mammalian circadian system can only be affected by light to the eyes. The exception is a recent study by Campbell and Murphy that reported phase shifts in humans to bright light applied with fiber-optic pads behind the knees (popliteal region). We tested whether this extraocular light stimulus could accelerate the entrainment of circadian rhythms to a shift of the sleep schedule, as occurs in shift work or jet lag. In experiment 1, the sleep/dark episodes were delayed 8h from baseline for 2 days, and 3h light exposures were timed to occur before the temperature minimum to help delay circadian rhythms. There were three groups: (1) bright (about 13,000 lux) extraocular light from fiber-optic pads, (2) control (dim light, 10–20 lux), and (3) medium-intensity (about 1000 lux) ocular light from light boxes. In experiment 2, the sleep/dark episodes were inverted, and extraocular light was applied either before the temperature minimum to help delay circadian rhythms or after the temperature minimum to help advance rhythms. Circadian phase markers were the salivary dim light melatonin onset (DLMO) and the rectal temperature minimum. There was no evidence that the popliteal extraocular light had a phase-shifting effect in either experiment. Possible reasons for phase shifts in the Campbell and Murphy study and not the current study include the many differences between the protocols. In the current study, there was substantial sleep deprivation before the extraocular light was applied. There was a large shift in the sleep/dark schedule, rather than allowing subjects to sleep each day from midnight to noon, as in the Campbell and Murphy study. Also, when extraocular light was applied in the current protocol, subjects did not experience a change from sleeping to awake, a change in posture (from lying in bed to sitting in a chair), or a change in ocular light (from dark to dim light). Further research is necessary to determine the conditions under which extraocular light might produce phase shifts in human circadian rhythms. (Chronobiology International, 17(6), 807–826, 2000).     

Factors Affecting Work Ability in Day and Shift‐Working Nurses

Satisfactory work ability is sustained and promoted by good physical and mental health and by favorable working conditions. This study examined whether favorable and rewarding work‐related factors increased the work ability among European nurses. The study sample was drawn from the Nurses' Early Exit Study and consisted of 7,516 nursing staff from seven European countries working in state‐owned and private hospitals. In all, 10.8% were day, 4.2% were permanent night, 20.9% were shift without night shift, and 64.1% were shift workers with night shifts. Participants were administered a composite questionnaire at baseline (Time 0) and 1 yr later (Time 1). The Work Ability Index (WAI) at Time 1 was used as the outcome measure, while work schedule, sleep, rewards (esteem and career), satisfaction with pay, work involvement and motivation, and satisfaction with working hours at Time 0 were included as potential determinants of work ability. Univariate and multivariate analyses were conducted after adjusting for a number of confounders (i.e., country, age, sex, type of employment, family status, and other job opportunities in the same area). Work schedule was not related to Time 1 changes in WAI. Higher sleep quality and quantity and more favorable psychosocial factors significantly increased work ability levels. Higher sleep quality and quantity did not mediate the effect of work schedule on work ability. No relevant interaction effects on work ability were observed between work schedule and the other factors considered at Time 0. As a whole, sleep and satisfaction with working time were gradually reduced from day work to permanent night work. However, scores on work involvement, motivation, and satisfaction with pay and rewards were the highest in permanent night workers and the lowest in rotating shift workers that included night shifts.