Shift work disorder in nurses--assessment, prevalence and related health problems

Background

This study investigates the prevalence of symptoms of shift work disorder in a sample of nurses, and its association to individual, health and work variables.

Methodology/Principal Findings

We investigated three different shift work disorder assessment procedures all based on current diagnostic criteria and employing symptom based questions. Crude and adjusted logistic regression analyses were performed with symptoms of shift work disorder as the dependent variable. Participants (n = 1968) reported age, gender, work schedule, commuting time, weekly work hours, children in household, number of nights and number of shifts separated by less than 11 hours worked the last year, use of bright light therapy, melatonin and sleep medication, and completed the Bergen Insomnia Scale, Epworth Sleepiness Scale, Global Sleep Assessment Questionnaire, Diurnal Scale, Revised Circadian Type Inventory, Dispositional Resilience (Hardiness) Scale – Revised, Fatigue Questionnaire, questions about alcohol and caffeine consumption, as well as the Hospital Anxiety and Depression Scale.

Conclusions/Significance

Prevalence rates of symptoms of shift work disorder varied from 32.4–37.6% depending on the assessment method and from 4.8–44.3% depending on the work schedule. Associations were found between symptoms of shift work disorder and age, gender, circadian type, night work, number of shifts separated by less than 11 hours and number of nights worked the last year, insomnia and anxiety. The different assessment procedures yielded similar results (prevalence and logistic regression analyses). The prevalence of symptoms indicative of shift work disorder was high. We argue that three symptom-based questions used in the present study adequately assess shift work disorder in epidemiological studies.     

Refurbishment of office buildings in New Zealand: identifying priorities for reducing environmental impacts

Purpose

In recent years, the building sector has highlighted the importance of operational energy and efficient resource management in order to reduce the environmental impacts of buildings. However, differences in building-specific properties (building location, size, construction material, etc.) pose a major challenge in development of generic policy on buildings. The aim of this study was to investigate the relationship between energy and resource management policies, and building-specific characteristics on environmental impacts of refurbished office buildings in New Zealand.

Methods

Life Cycle Assessment (LCA) was performed for 17 office buildings operating under seven representative climatic conditions found in New Zealand. Each building was assessed under four policy scenarios: (i) business-as-usual, (ii) use of on-site photovoltaic (PV) panels, (iii) electricity supply from a renewable energy grid, and (iv) best practice construction activities adopted at site. The influence of 15 building-specific characteristics in combination with each scenario was evaluated. The study adopted regression analysis, more specifically Kruskal-Wallis and General Additive Modeling (GAM), to support interpretation of the LCA results.

Results and discussion

All the chosen policies can significantly contribute to climate change mitigation as compared to business-as-usual. However, the Kruskal-Wallis results highlight policies on increasing renewable energy sources supplying national grid electricity can substantially reduce the impacts across most environmental impact categories. Better construction practices should be prioritized over PV installation as use of on-site PV significantly increases the environmental impacts related to use of resources. The GAM results show on-site PV could be installed in low-rise buildings in regions with long sunshine hours. The results also show the strong influence of façade elements and technical equipment in determining the environmental performance of small and large buildings, respectively. In large multi-storied buildings, efficient HVAC and smaller window area are beneficial features, while in small buildings the choice of façade materials with low embodied impacts should be prioritized.

Conclusions

In general, the study highlighted the importance of policies on increasing renewable energy supply from national grid electricity to substantially reduce most of the impacts related to buildings. In addition, the study also highlighted the importance of better construction practices and building-specific characteristics to reduce the impacts related to resource use. These findings can support policy makers to prioritize strategies to improve the environmental performance of existing buildings in New Zealand and in regions with similar building construction and climate.

     

Combining environmental exposure and genetic effect measurements in health outcome assessment.

The presence of overwhelming difficulties in assessing the extent or even the presence of a causal association between modern environmental exposures and disease has promoted the use of more complex models in the design of human biomonitoring studies. The concatenation of environmental exposure, genetic effect and individual susceptibility is a key issue in the assessment of risks for populations exposed to environmental pollutants. The use of a biological event laying in the causal pathway from exposure to outcome as surrogate end-point of disease, can potentially anticipate clinical diagnosis, offering a number of possibilities for application of preventive measures. Numerous biomarkers are currently employed to study human populations exposed to environmental carcinogens, among these, the frequency of chromosomal aberration (CA) in peripheral blood lymphocytes has the most abundant literature linking a genetic effect with the occurrence of cancer. Findings from recent epidemiological studies which have followed-up a large group of healthy subjects screened for CAs have lent further support to the use of chromosomal breakage as a relevant biomarker of cancer risk. The applicability of surrogate end-points of cancer on an individual basis thus far seems to be limited to few examples. On the other hand, from a public health outlook, increases in the frequency of surrogate end-points are suggestive of an increased risk of cancer, and for validated biomarkers such as CAs intervention policies and actions in exposed populations showing increased frequency of these end-points should be always recommended.     

Comparison of the two different phosphagen systems in the lugworm Arenicola marina

The different phosphagen systems in the lugworm Arenicola marina, the phosphotaurocyamine/taurocyamine kinase system of the body wall and the phosphocreatine/creatine kinase system of the spermatozoa, have been investigated to answer the question whether the change reflects different functional modes of these phosphagen systems. Enzyme analyses have shown that in contrast to the body wall taurocyamine kinase, creatine kinase of spermatozoa exists in at least two different forms which are compartmented in the mitochondria (creatine kinase I) and in the flagellum (creatine kinase II). Creatine kinase I is strongly attached to cell structures which require detergents and high phosphate concentrations for solubilization. The affinities of taurocyamine kinase and creatine kinase for all substrates are very similar except the extremely high K _m for creatine of both creatine kinase I and II. The level of creatine in spermatozoa is fivefold higher than taurocyamine in the body wall at similar phosphorylation potential (ATP/ADO_free) and ATP-buffer capacity (phosphagen/ATP), reflecting the higher equilibrium constants of the creatine kinase reaction compared to that of the taurocyamine kinase reaction (Ellington 1989). The high creatine concentration gives the phosphocreatine/creatine kinase system an advantage over the phosphotaurocyamine/taurocyamine kinase system for transport of energyrich phosphate at high phosphorylation potential by increasing the radial diffusion flux. The maximum diffusive flux of free ADP in spermatozoa is three orders of magnitude below the respiratory ATP production while the creatine flux would allow an unlimited energy transport over the long diffusion distance. In lugworm body wall, however, the low ATP turnover and the low diffusion distances between mitochondria and myosin-ATPases do not require a phosphagen shuttle.Abbreviations ADP _free cytoplasmic adenosine diphosphate - Ap ₅ A P₁, P₅-di(adenosine-5-) pentaphosphate - AK arginine kinase - CK creatine kinase (EC 2.7.3.2) - DTT dithiothreitol - GAPDH glyceraldehydephosphate dehydrogenase (EC 1.2.1.12) - HOADH 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) - IEP isoelectric point - MIM mitochondria isolating medium - P _i-free cytoplasmic inorganic phosphate - (P)Arg (phospho)arginine - (P)Cr (phospho)creatine - (P)Tc (phospho)taurocyamine - SEM scanning electron microscopy - TK taurocyamine kinase - TEM transmission electron microscopy     

Comparison of structure-activity relations of corazonin using two different bioassay systems

The structure-activity relations of [His(7)]-corazonin were studied using two different bioassay systems; i.e. inhibitory effect on spinning rate in the silkworm, Bombyx mori, and darkening response in albino nymphs of the migratory locust, Locusta migratoria. Deletion of the N-terminus, shortening of the peptide and single amino acid substitutions reduced activity in a similar manner except for the minimum effective dose in the two insects. The results also revealed that the residues at position 1, 3 and 5 were particularly important for biological activity. Despite the different physiological affects, the two insect species exhibited similar structure-activity relationships, suggesting that they might have similar receptor systems.     

Comparison of motor activity measured by two different methods: optical and inductive systems

Motor activity of twelve rats was recorded by means of two different methods, an optical detection method (ODM) as a mass-independent system and an inductive detection method (IDM) as a mass-dependent system. The chronograms and power spectra obtained from the data were compared to find the essential aspects of both methods. The results suggest that the ODM is more appropriate in studying ultradian rhythms and small motor activity changes, while IDM is better suited to the study of circadian rhythms and gross motor activity variations.     

Sequence-based study of two related proteins with different folding behaviors

Z(SPA-1) is an engineered protein that binds to its parent, the three-helix-bundle Z domain of staphylococcal protein A. Uncomplexed Z(SPA-1) shows a reduced helix content and a melting behavior that is less cooperative, compared with the wild-type Z domain. Here we show that the difference in folding behavior between these two sequences can be partly understood in terms of an off-lattice model with 5-6 atoms per amino acid and a minimalistic potential, in which folding is driven by backbone hydrogen bonding and effective hydrophobic attraction.     

Contrasting demographic history and population structure in Capsella rubella and Capsella grandiflora, two closely related species with different mating systems

Both mating system and population history can have large impacts on genetic diversity and population structure. Here, we use multilocus sequence data to investigate how these factors impact two closely related Brassicaceae species: the selfing Capsella rubella and the outcrossing C. grandiflora. To do this, we have sequenced 16 loci in approximately 70 individuals from 7 populations of each species. Patterns of population structure differ strongly between the two species. In C. grandiflora, we observe an isolation-by-distance pattern and identify three clearly delineated genetic groups. In C. rubella, where we estimate the selfing rate to be 0.90-0.94, the pattern is less clear with some sampling populations forming separate genetic clusters while others are highly mixed. The two species also have divergent histories. Our analysis gives support for a bottleneck approximately 73 kya (20-139 kya) in C. rubella, which most likely represents speciation from C. grandiflora. In C. grandiflora, there is moderate support for the standard neutral model in 2 of 3 genetic clusters, while the third cluster and the total data set show evidence of expansion. It is clear that mating system has an impact on these two species, for example affecting the level of genetic variation and the genetic structure. However, our results also clearly show that a combination of past and present processes, some of which are not affected by mating system, is needed to explain the differences between C. rubella and C. grandiflora.     

Comparison of human uterine cervical electrical impedance measurements derived using two tetrapolar probes of different sizes

Background  

We sought to compare uterine cervical electrical impedance spectroscopy measurements employing two probes of different sizes, and to employ a finite element model to predict and compare the fraction of electrical current derived from subepithelial stromal tissue.     

Comparison of two plethysmography systems in assessment of forearm blood flow.

Venous occlusion plethysmography is widely used to assess forearm blood flow (FBF). We compared the established Hokanson system (HEC4) with a newly developed Filtrass 2001 system (F2001). The HEC4 uses mercury-in-Silastic strain gauges, whereas F2001 detects volume changes with a nonmercury linear displacement device. The aim of this study was to evaluate the new F2001 against the HEC4 in terms of repeatability and systematic bias. Ten subjects were studied on 4 separate days in random order using either the HEC4 on both arms, the F2001 on both arms, the HEC4 on the right arm with the F2001 on the left, or the F2001 on the right arm and the HEC4 on the left. Stroop's colored word conflict test and postocclusive hyperemia were used to increase FBF, and lower body negative pressure was used to lower FBF. Stroop's colored word conflict test and lower body negative pressure increased (24.6 +/- 1.5%, n = 240, P < 0.0001) and decreased (18.7 +/- 0.8%, n = 240, P < 0.0001) FBF, respectively. Postocclusive hyperemia after occlusion times of 5, 8, and 13 min substantially increased FBF by 390 +/- 86, 756 +/- 217, and 851 +/- 132%, respectively. Repeatability was not different between the devices (0.10 +/- 2.37 vs. -0.47 +/- 1.92 l/min, n = 125, P > 0.05), and there was no systematic bias. The F2001 is a newly developed plethysmography system that does not utilize mercury and is suitable for assessing changes of FBF in physiological studies.     

Comparison of chemoreflex gains obtained with two different methods in cats

This study investigates the correspondence between results of the ventilatory response to CO2 obtained using the technique of dynamic end-tidal CO2 forcing (DEF) and results obtained using the technique of artificial brain stem perfusion (ABP). The DEF technique separates the dynamic ventilatory response into a slow and fast component with gains g1 and g2 as well as the extrapolated CO2 tension at zero ventilation (Bk). The ABP technique results in steady-state central (Sc) and peripheral (Sp) chemoreflex gains and extrapolated CO2 tension at zero ventilation (B). Experiments were performed on 14 alpha-chloralose-urethan anesthetized cats. A wide range of relative peripheral chemosensitivities was obtained by subjecting eight cats to normoxic and three cats to hypoxic CO2 challenges and three cats to both conditions. Statistical analysis of the experimental data showed that the vectors (g1, g2, Bk) and (Sc, Sp, B) for each cat did not differ significantly (P = 0.56). This was also the case for the vectors [g2/(g1 + g2), Bk] and [Sp/(Sc + Sp), B] (P = 0.21). We conclude that in the DEF experiments the slow ventilatory response to isoxic changes in end-tidal CO2 can be equated with the central chemoreflex loop and the faster ventilatory response to the peripheral chemoreflex loop. The agreement between the two techniques is good.     

Comparison of two different actigraphs with polysomnography in healthy young subjects

The present study aimed to compare two commercially available actigraphs, with a concurrent polysomnographic (PSG) recording. Twelve healthy volunteers (six women; age range 19-28 yrs) simultaneously wore the Basic Mini-Motionlogger^® and Actiwatch^® for seven overnight polysomnographic recordings. Comparisons of the following sleep measures were focused on: sleep onset latency (SOL), total sleep time, wake after sleep onset, and sleep efficiency. Both devices underestimated SOL in comparison to PSG, but they had similar performance compared to PSG for the other sleep measures. A limit of the study is that the results can be only generalized to healthy young subjects.     

Comparison of two synthetic progesterones on ventilation in normal males: CMA vs. MPA

We administered chlormadinone acetate (CMA), medroxyprogesterone acetate (MPA), and placebo to 16 normal male subjects using a randomized double-blind crossover study. After CMA administration, minute alveolar ventilation increased by +1.04 +/- 0.22 (SE) 1/min (P less than 0.05) accompanied by decrements of arterial PCO2 (-4.0 +/- 1.0 Torr) (P less than 0.01) and [HCO3-] (-2.1 +/- 0.05 mM/l) (P less than 0.01). On the other hand, in the MPA runs the corresponding changes of the above parameters were +0.71 +/- 0.21 l/min (P less than 0.05), -2.9 +/- 0.6 Torr (P less than 0.01), and -1.3 +/- 0.3 mM/l (P less than 0.01), respectively. The slopes of hypoxic ventilatory and occlusion pressure response lines remained unchanged in hypocapnia after CMA or MPA ingestion, but they increased when entidal PCO2 was adjusted to the predrug level. The hypercapnic ventilatory and occlusion pressure response lines merely shifted to the left without changing their slopes with these agents. No significant differences in all the above parameters were found between CMA and MPA runs. We concluded that in the normal males the effect of CMA on ventilation was similar to that of MPA, despite the fact that the luteinizing activity of CMA was reported to be approximately 10 times higher than the latter.