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PubMed2006

Proteome analysis of yeast response to various nutrient limitations.

We compared the response of Saccharomyces cerevisiae to carbon (glucose) and nitrogen (ammonia) limitation in chemostat cultivation at the proteome level. Protein levels were differentially quantified using unlabeled and 15N metabolically labeled yeast cultures. A total of 928 proteins covering a wide range of isoelectric points, molecular weights and subcellular localizations were identified. Stringent statistical analysis identified 51 proteins upregulated in response to glucose limitation and 51 upregulated in response to ammonia limitation. Under glucose limitation, typical glucose-repressed genes encoding proteins involved in alternative carbon source utilization, fatty acids beta-oxidation and oxidative phosphorylation displayed an increased protein level. Proteins upregulated in response to nitrogen limitation were mostly involved in scavenging of alternative nitrogen sources and protein degradation. Comparison of transcript and protein levels clearly showed that upregulation in response to glucose limitation was mainly transcriptionally controlled, whereas upregulation in response to nitrogen limitation was essentially controlled at the post-transcriptional level by increased translational efficiency and/or decreased protein degradation. These observations underline the need for multilevel analysis in yeast systems biology.

Ammonia↗
PubMed1998

The growth of the human embryo. A longitudinal biometric assessment from 7 to 12 weeks of gestation.

OBJECTIVES: Longitudinal studies of multiple parameters in the first trimester for assessment of embryonic growth are lacking. This study's aim was to register changes in growth over time, by taking several measurements of embryos on successive occasions and evaluating these changes by longitudinal analysis. DESIGN: This prospective longitudinal study describes the normal embryonic growth in vivo. Inclusion criteria were non-smoking women with single uneventful pregnancies, regular menstrual periods (28-30 days) and no hormone therapy in the 3 months prior to the pregnancy. Exclusion criteria were pregnancy complications such as diabetes, pre-eclampsia, delivery of preterm or growth-restricted infants. Of 36 recruited pregnant women, 29 met these criteria. Each pregnancy was examined five times between 7 and 12 weeks of gestation. This resulted in a two-level data set, where level 1 consisted of the observations and level 2 consisted of the individuals. The longitudinal data were analyzed with a software package specially created for multilevel analysis. RESULTS: The growth of the biparietal diameter (BPD), occipitofrontal diameter (OFD), mean abdominal diameter (MAD), chorionic cavity diameter and amniotic cavity diameter was constant; the growth of the crown-rump length (CRL) and the yolk sac diameter was not constant. Variation in the data sets was mainly caused by variation between the embryos/fetuses. CONCLUSIONS: The measured parameters except for the yolk sac showed a high degree of uniformity with virtually the same growth velocities. The yolk sac demonstrated uniform growth until week 10 only. Differences between the gestational age based on the last menstrual period and the true gestational age, and/or differences in the early growth of the embryos before the start of the study at 7 weeks, may have contributed to the variation between the individuals.

Adult↗
PubMed2005

Neighbourhood deprivation and alcohol consumption: does the availability of alcohol play a role?

BACKGROUND: Previous studies suggest that the physical availability of alcohol may mediate the association between neighbourhood-level material deprivation and alcohol consumption. This study tests the relationships between neighbourhood-level deprivation, alcohol availability, and individual-level alcohol consumption using a multilevel analysis. METHODS: Data are from cross-sectional surveys conducted between 1979 and 1990 as part of the Stanford Heart Disease Prevention Program (SHDPP). Women and men (n = 8197) living in four northern/central California cities and 82 neighbourhoods were linked to neighbourhood deprivation variables derived from the US census (e.g. unemployment, crowded housing) and to measures of alcohol availability (density of outlets in the respondent's neighbourhood, nearest distance to an outlet from the respondent's home, and number of outlets within a half mile radius of the respondent's home). Separate analyses were conducted for on- and off-sale outlets. RESULTS: The most deprived neighbourhoods had substantially higher levels of alcohol outlet density than the least deprived neighbourhoods (45.5% vs 14.8%, respectively). However, multilevel analyses showed that the least deprived neighbourhoods were associated with the heaviest alcohol consumption, even after adjusting for individual-level sociodemographic characteristics (OR 1.30, CI 1.08-1.56). Alcohol availability was not associated with heavy drinking and thus did not mediate the relationship between neighbourhood deprivation and heavy alcohol consumption. CONCLUSIONS: Although alcohol availability is concentrated in the most deprived neighbourhoods, women and men in least deprived neighbourhoods are most likely to be heavy drinkers. This mismatch between supply and demand may cause people in the most deprived neighbourhoods to disproportionately suffer the negative health consequences of living near alcohol outlets.

Adult↗
PubMed2006

Open-book tests to complement assessment-programmes: analysis of open and closed-book tests.

Today's health sciences educational programmes have to deal with a growing and changing amount of knowledge. It is becoming increasingly important for students to be able to use and manage knowledge. We suggest incorporating open-book tests in assessment programmes to meet these changes. This view on the use of open-book tests is discussed and the influence on test quality is examined. To cope with the growing amount of medical knowledge, we have divided the body of knowledge into core knowledge, which students must know without need for references, and backup knowledge, which students need to understand and use properly with the help of references if so desired. As a result, all tests consist of a subtest for reproduction and understanding of core knowledge (a closed-book test) and a subtest for the ability to understand and manage backup knowledge (an open-book test). Statistical data from 14 such double-subtest exams for first and second-year students were analyzed for two cohorts (N = 435 and N = 449) with multilevel analysis, in accordance with generalizability theory. The reliability of the open and closed-book sections of the separate tests varied between 0.712 and 0.850. The open-book items reduce reliability somewhat. The estimated disattenuated correlation was 0.960 and 0.937 for cohorts 1 and 2 respectively. It is concluded that the use of open-book items with closed-book items slightly decreases test reliability but the overall index is acceptable. In addition, open and closed-book sections are strongly positively related. Therefore, open-book tests could be helpful in complementing today's assessment programmes.

Cohort Studies↗
PubMed2004

The spinal cord in multiple sclerosis: relationship of high-spatial-resolution quantitative MR imaging findings to histopathologic results.

PURPOSE: To correlate quantitative magnetic resonance (MR) imaging data (ie, relaxation times and magnetization transfer ratios [MTRs]) with histopathologic findings of demyelination and axonal disease in cervical spinal cord specimens from patients with multiple sclerosis (MS) and control subjects. MATERIALS AND METHODS: Formaldehyde-fixed cervical spinal cord specimens from 11 patients with MS-three men and eight women (mean age at death, 66 years +/- 11.3 [standard deviation])-and two female control subjects without neurologic disease (83 and 41 years of age at death) were examined at 4.7 T. Relaxation time measurements and MTR mapping were performed. Analyses included the whole cord area and region-of-interest measurements. Histopathologic analyses included semiquantitative myelin and quantitative axonal analysis. RESULTS: Compared with control specimens (P < .001, analysis of variance), specimens from patients with MS had smaller cord areas (mean area, 59.0 mm(2) +/- 12.5 vs 72.7 mm(2) +/- 10.0), significant prolongation of T1 (mean prolongation, 30%) and T2 (mean prolongation, 13%), and decreased MTRs (mean, 10.5%). Within MS specimens, 58% of the white matter area displayed signal intensity abnormalities on intermediate-weighted MR images. The number of axons in normal-appearing white matter in MS specimens was, on average, 46% lower than the number of axons in white matter in control specimens. All quantitative MR parameters correlated well with demyelination; the correlation with T2 relaxation time was the strongest (r = 0.77, Spearman and Kendall nonparametric correlations). By contrast, quantitative MR parameters correlated less well with axonal density; the correlation with T2 relaxation time was the strongest (r = -0.44, Spearman and Kendall nonparametric correlations). Multilevel analysis, corrected for age and MS phenotype, could not result in a model explaining axonal density on the basis of quantitative MR parameters when myelin density was included as a predictor. CONCLUSION: Changes in quantitative MR imaging parameters in the cervical spinal cord in MS are mainly determined by demyelination and do not reflect axonal disease well.

Adult↗
PubMed2005

[Blood glucose control in diabetes patients seen in primary health care centers].

OBJECTIVE: To identify factors associated to poor glycemic control among diabetic patients seen at primary health care centers. METHODS: A cross-sectional study was carried out in a sample of 372 diabetic patients attending 32 primary health care centers in southern Brazil. Data on three hierarchical levels of health unit infrastructure, medical care and patient characteristics were collected. RESULTS: The frequency of poor glycemic control was 50.5%. Multivariate analysis (multilevel method) showed that patients with body mass indexes below 27 kg/m2, patients on oral hypoglycemic agents or insulin, and patients diagnosed as diabetic over five years prior to the interview were more likely to present poor glycemic control when compared to their counterparts. CONCLUSIONS: Given the hierarchical data structuring, all associations found suggest that factors associated to hyperglycemia are related to patient-level characteristics.

Adult↗
PubMed2006

Vitamin G: effects of green space on health, well-being, and social safety.

BACKGROUND: Looking out on and being in the green elements of the landscape around us seem to affect health, well-being and feelings of social safety. This article discusses the design of a research program on the effects of green space in the living environment on health, well-being and social safety. METHODS/DESIGN: The program consists of three projects at three different scales: at a macro scale using data on the Netherlands as a whole, at an intermediate scale looking into the specific effect of green space in the urban environment, and at micro scale investigating the effects of allotment gardens. The projects are observational studies, combining existing data on land use and health interview survey data, and collecting new data through questionnaires and interviews. Multilevel analysis and GIS techniques will be used to analyze the data. DISCUSSION: Previous (experimental) research in environmental psychology has shown that a natural environment has a positive effect on well-being through restoration of stress and attentional fatigue. Descriptive epidemiological research has shown a positive relationship between the amount of green space in the living environment and physical and mental health and longevity. The program has three aims. First, to document the relationship between the amount and type of green space in people's living environment and their health, well-being, and feelings of safety. Second, to investigate the mechanisms behind this relationship. Mechanisms relate to exposure (leading to stress reduction and attention restoration), healthy behavior and social integration, and selection. Third, to translate the results into policy on the crossroads of spatial planning, public health, and safety. Strong points of our program are: we study several interrelated dependent variables, in different ordinary settings (as opposed to experimental or extreme settings), focusing on different target groups, using appropriate multilevel methods.

Attention↗
PubMedDate not supplied

[Organizational appropriateness of recoveries: results of the evaluation of recoveries by AEP/PRUO at the Careggi Hospital in Florence in 1995-1998].

The organizational appropriateness of hospital stays is an expression of a hospital's efficiency and aim of the management control. The AEP (American Version)/PRUO (Italian Version) protocol is specific for measuring the organizational appropriateness of hospital stays. The aim of this study is the comparative analysis of the organizational appropriateness of hospital stays in Careggi Hospital of Florence and in all hospital Departments in 1995 and 1998. In 1998 the AEP/PRUO protocol was applied to 2148 samples of hospital stays out of 38,968 eligible hospitalizations, and in 1995 a sample of 1989 hospital stays out of 35,108. In 1998 2,148 admissions and 15,338 days of hospitalization were tested. In 1995, 1989 admission days and 12,264 days of hospitalization were tested, 63 departments were studied. In 1995 the first edition of the protocol was applied, in 1998 the second. A sample of 218 of the 1998 hospital stays was tested with both editions to evaluate the impact of differences. In 1998, with the second edition of the protocol, the inappropriateness rate of admission days and hospitalization days and the rate of in-patients inappropriate hospital stays was respectively 38.0%, 43.8% and 18.5%. Compared with 1995 results, the rates increased +6.2%, 6% and +7.5% respectively. Instead, with the first edition of the protocol, the rates were 29.7%, 37.6% and 10.7% and, compared with 1995, they were reduced -2.1%, -0.6% and -0.3%. The longitudinal multilevel analysis has allowed the evaluation of the performance of each department.

Convalescence↗
PubMed2005

Disparities despite coverage: gaps in colorectal cancer screening among Medicare beneficiaries.

BACKGROUND: Despite its effectiveness in reducing mortality, colorectal cancer (CRC) screening rates are low, especially among low-income and minority groups; however, physician recommendation can increase screening rates. METHODS: We performed a multilevel analysis of the Medicare Current Beneficiary Survey data linked to Medicare claims and the Area Resource File to identify determinants of racial and socioeconomic disparities in CRC screening among 9985 Medicare Parts A and B beneficiaries with a usual physician. Recent CRC screening was defined as receipt of either a home fecal occult blood test, flexible sigmoidoscopy, or colonoscopy at recommended intervals. RESULTS: Unadjusted rates of screening were 48% for white and 39% for black beneficiaries (P<.001). Racial differences in CRC screening receipt were eliminated after adjustment for socioeconomic status as measured by income and education. Socioeconomic status disparities decreased but remained significant after adjustment for personal and health system factors. Awareness of CRC (adjusted odds ratio, 2.76; 95% confidence interval, 2.29-3.33) and having a primary care generalist (vs another specialist) as one's usual physician (adjusted odds ratio, 1.31; 95% confidence interval, 1.12-1.53) were associated with higher odds of screening, controlling for other factors. The odds of screening were also higher among those whose usual physician was rated more highly on information-giving skills. CONCLUSIONS: Racial differences in CRC screening rates among Medicare beneficiaries with a usual physician are explained by differences in socioeconomic status. Beneficiaries with a primary care generalist as their usual physician had higher rates of CRC screening receipt. Increased efforts to make Medicare beneficiaries aware of the benefits of CRC screening may capitalize on the associations found in this study between CRC knowledge, physician information giving, and timely screening.

Aged↗
PubMed2005

Violent behavior by girls reporting violent victimization: a prospective study.

OBJECTIVE: To assess the relationships between individual victimization and neighborhood-level violence on subsequent violent perpetration by adolescent girls in a community-based sample. DESIGN: Longitudinal, multilevel analysis of data collected by the Project on Human Development in Chicago Neighborhoods. Three in-home interviews were conducted approximately 24 months apart between November 1995 and January 2002 with youth and their caregivers. Community-level data also were collected in 1995 from a random sample of Chicago residents. Hierarchical regression models and propensity scores were used. SETTING: Families and neighborhoods in Chicago. PARTICIPANTS: Population-based sample of 637 girls, ages 9 to 15 years at baseline, and the neighborhoods in which they resided. This sample is diverse in race/ethnicity, socioeconomic status, family structure, and neighborhood characteristics. MAIN OUTCOME MEASURE: Self-reports of violent behavior in the 12 months before the third interview. RESULTS: At baseline, 38% of the girls reported perpetrating at least 1 violent behavior in the prior 12 months, 28% reported past year violent behavior at the first follow-up interview, and 14% reported past year violent behavior at the third interview. The odds of violent behavior were 2.2 times higher among girls who reported prior violent victimization, after prior confounding factors and baseline violent behavior were controlled (95% confidence interval, 1.3- 4.4). Homicides and concentrated poverty in girls' neighborhoods also were associated with aggression by girls. CONCLUSIONS: Improving safety in communities and homes may reduce rates of violent perpetration by adolescent girls. Study results suggest that, to facilitate identification of and healing among adolescent survivors of violence, practitioners should recognize perpetration of violence as potential sequelae of prior violent victimization.

Adolescent↗
PubMed1997

Comparative evaluation of [3H]WIN 35428 and [3H]GBR 12935 as markers of dopamine innervation density in brain.

WIN 35428 and GBR 12935, two uptake blocker ligands of the membrane transporter for dopamine (DA), were evaluated as quantitative markers of DA innervation density in CNS tissue. From alternate rat brain slices respectively processed for either light microscope or film autoradiography, counts of DA axon terminals (varicosities) labeled by uptake/storage of [3H]DA were matched with densitometric measurements of the specific binding of [3H]WIN 35428 and [3H]GBR 12935 in the same anatomical areas. The relation between the two parameters was examined in 1) the normal cingulate cortex; 2) the neostriatum severely DA-denervated by unilateral intramesencephalic injections of 6-hydroxydopamine; and 3) the neostriatum, partly DA-reinnervated by an intrastriatal graft of fetal mesencephalic neurons after prior 6-hydroxydopamine lesion. For technical reasons, the hyperdense DA innervation of normal striatum was not amenable to such correlative testing. Data were subjected to multilevel analysis. Specific [3H]WIN binding at 37 degrees C was tightly and linearly correlated with the number of DA varicosities over the full range of DA innervation densities tested. The regression lines for intact cortex and for DA-denervated as well as DA-reinnervated neostriatum had the same slope and crossed the ordinate near zero. In contrast, [3H]GBR 12935 binding at 37 degrees C showed no correlation with the number of DA varicosities. A linear correlation could be obtained after incubation with [3H]GBR 12935 at 4 degrees C in the presence of ZnSO4, but the intercept of this regression line remained significantly above zero at origin, indicating extraneous binding to non-DA transporter sites. Providing that the hyperdense DA innervation of the normal neostriatum does not generate a particular problem in vivo as it does in vitro. WIN 35428, but not GBR 12935, might satisfy the selectivity and sensitivity requirements of a quantitative marker of DA innervation density for eventual use in positron emission tomographic studies.

Animals↗
PubMed2004

Subcutaneous octreotide in cluster headache: randomized placebo-controlled double-blind crossover study.

Current practical evidence-based acute treatments of cluster headache are limited to subcutaneous and intranasal formulations of sumatriptan, and oxygen. Two small randomized, double-blind trials suggested efficacy of somatostatin in cluster headache. We sought to determine whether octreotide, a somatostatin analog, is effective in the abortive treatment of acute cluster headache. Patients with episodic and chronic cluster headache, as defined by the International Headache Society, were recruited to a double-blind placebo-controlled crossover study. Patients were instructed to treat two attacks of at least moderate pain severity, with at least a 24-hour break, using subcutaneous octreotide microg or matching placebo. The primary end point was the headache response defined as very severe, severe, or moderate pain becomes mild or nil, at 30 minutes. The primary end point was examined using a multilevel analysis approach. A total of 57 patients were recruited of whom 46 provided efficacy data on attacks treated with octreotide and 45 with placebo. The headache response rate with subcutaneous octreotide was 52%, whereas that with placebo was 36%. Modeling the treatment outcome as a binomial where response was determined by treatment, using the patient as the level 2 variable, and considering period effect, sex, and cluster headache type as other variables of interest, we found that the effect of subcutaneous octreotide 100 microg was significantly superior to placebo (p < 0.01). Subcutaneous octreotide 100 microg is effective in the acute treatment of cluster headache when compared with placebo. Nonvasconstrictor treatment of acute cluster headache is possible.

Adolescent↗
PubMed2006

Multilevel grouped regression for analyzing self-reported health in relation to environmental factors: the model and its application.

A method for modeling the relationship of polychotomous health ratings with predictors such as area characteristics, the distance to a source of environmental contamination, or exposure to environmental pollutants is presented. The model combines elements of grouped regression and multilevel analysis. The statistical model describes the entire response distribution as a function of the predictors so that any measure that summarizes this distribution can be calculated from the model. With the model, polychotomous health ratings can be used, and there is no need for a priori dichotomizing such variables which would lead to loss of information. It is described how, according to the model, various measures describing the response distribution are related to the exposure, and the confidence and tolerance intervals for these relationships are presented. Specific attention is given to the incorporation of random factors in the model. The application that here serves as an example, concerns annoyance from transportation noise. Exposure-response relationships obtained with the described method of modeling are presented for aircraft, road traffic, and railway noise.

Algorithms↗
PubMed2005

Maturation of escape circuit function during the early adulthood of cockroaches Periplaneta americana.

During postembryonic development of insects, sensorimotor pathways, which generate specific behaviors, undergo maturational changes. It is less clear whether such pathways are typically stable, or undergo further maturation, during the adult stage. In the present study, we have examined this issue by multilevel analysis of a simple model system, the escape behavior of the cockroach, from identified synapses to behavior. We show that the escape system is highly responsive immediately after the molt to adulthood, but that the latency of escape responses was not at its typical value immediately after the molt to adult. The latency of escape behavior increased over the first 30 days of adult life, perhaps indicating maturational adjustments of the escape sensorimotor pathway. The first station in the escape circuitry is the synaptic connections between the cercal wind receptors and the giant interneurons. We measured unitary excitatory synaptic potentials between single sensory neurons and an identified giant interneuron (GI(2)). We found a decrease in the synaptic strength between identified cercal hairs from a single column and GI(2) over the first month after the adult molt. Consequently, the latency and the number of action potentials of GI(2) in response to natural stimuli increased and decreased respectively during this time. Thus, we show that both behavioral performance and the wind sensitivity of GI(2) decreased over the first month after molt. We conclude that the cockroach escape system undergoes further sensorimotor maturation over a period of 1 month, and that cellular changes correlate with, or predict, some changes in behavioral performance.

Action Potentials↗
PubMed1995

Evaluation of three transporter ligands as quantitative markers of serotonin innervation density in rat brain.

Direct counting of axon terminals (varicosities) labeled by uptake/storage of a tritiated monoamine provides a means to test radioligands of the corresponding membrane transporter as quantitative markers of regional monoamine innervation density in brain tissue. In autoradiographs from alternate rat brain slices, counts of [3H]5-HT-labeled axon terminals were matched with densitometric measurements of the specific binding of tritiated cyanoimipramine (CYI), citalopram (CITAL), and 6-nitroquipazine (6-NTQ), under conditions of hypo-, normo-, or hyper-5-HT innervation of the neostriatum. A total of 267 pairs of data were subjected to a multilevel analysis (iterative generalized least square procedure). With all three ligands, there was a linear relationship between the density of 5-HT innervation and the density of specific binding and no change in the slope of the regression lines as a function of 5-HT innervation density. Thus, none of these ligands gave any sign of down- or up-regulation of the 5-HT transporter consequent to 5-HT hypo- or hyper-innervation. The regression lines for CYI and CITAL were not significantly different from one another and crossed the ordinate near zero, whereas the regression line for 6-NTQ was less steep and had a higher intercept with the ordinate. In addition, the dispersion of values around the regression line (residuals) was lower with CYI and CITAL than 6-NTQ. It was concluded that both CYI and CITAL may serve as quantitative markers of 5-HT innervation density, at least in vitro, whereas 6-NTQ demonstrates a certain lack of specificity and sensitivity. Further work will be needed to assess the potential of CYI and CITAL for positron emission tomographic studies of living brain. Such empirical testing should also be applicable for screening radioligands of the dopamine or the noradrenaline transporters.

Animals↗
PubMed2005

First-trimester fetuses with increased nuchal translucency do not show altered intracardiac flow velocities.

OBJECTIVE: To study intracardiac flow velocities in first-trimester fetuses with normal nuchal translucency thickness (NT) and those with increased NT. METHODS: Ultrasound examinations were performed in 85 normal fetuses and 45 fetuses with NT > 95(th) percentile. Follow-up was complete and postmortem examination was performed on terminated pregnancies. Flow velocities during the early (e-wave) and late (a-wave) peaks across the tricuspid and mitral valves were measured and compared, using multilevel analysis, between the fetuses with normal and those with increased NT. In the group with increased NT, fetuses with and without a heart defect irrespective of the karyotype were compared, and in this group, euploid and aneuploid fetuses were compared, irrespective of the presence of a heart defect. RESULTS: No difference in intracardiac flow velocities was found between fetuses with normal and those with increased NT. Within the group of fetuses with increased NT, there was no difference between the fetuses with and without a cardiac defect. However, comparison of aneuploid with euploid fetuses within the group with increased NT showed that both the e-wave and a-wave peaks were decreased significantly by 3.03 cm/s and 5.95 cm/s, respectively, across the tricuspid valve, and by 3.47 cm/s and 5.92 cm/s, respectively, across the mitral valve (P < 0.05). The most common cardiac malformations were septal defects. CONCLUSION: There is no difference in intracardiac blood flow velocities between normal fetuses and those with increased NT. This contradicts the theory that NT is caused by impaired atrial contraction or cardiac failure. In fetuses with increased NT, those with aneuploidy show a decreased e-wave and a-wave compared with euploid fetuses. This cannot, however, be explained by the presence of cardiac defects, because there is no difference between fetuses with and without a cardiac defect. Therefore, we hypothesize that the relationship between enlarged NT and cardiac defects can only be explained by a developmental process that coexists at this period of gestation and is linked to cardiovascular development.

Blood Flow Velocity↗
PubMed2001

School-related stress, support, and subjective health complaints among early adolescents: a multilevel approach.

This study investigated the relationship between shared psychosocial school environment and subjective health complaints. A representative sample of 1585 Norwegian grade 8 students (mean age 13.5 years) from 82 schoolclasses completed scales on health complaints, academic stress, the teacher and classmate support scale, decision control, and noise and disturbance in class. Multilevel analysis (MlwiN) revealed that level of health complaints varied across schoolclasses (ICC=5.6%). School class differences in psychosocial environment accounted for 40% of the between-schoolclass variance in health complaints. Tests of cross-level interaction showed a statistically significant interaction between mean schoolclass-level of classmate support and individual level of academic stress. Findings suggest that shared schoolclass contextual factors may have main and stress-moderating effects on adolescent health complaints.

Adaptation, Psychological↗
PubMed2000

Cortisol secretion throughout the day, perceptions of the work environment, and negative affect.

The effects of explanatory variables derived from a work stress model (the effort-reward imbalance model) on salivary cortisol were assessed. A multilevel analysis was used to distinguish the effects of single occasion and multiple occasion measurements of work stress and effect on cortisol. The single (or cross-sectional) factors include Effort-Reward Imbalance (ERI), need for control, negative affect, and other enduring factors (type of occupation, gender, and smoking). The multiple occasion measurements include momentary negative mood, Momentary Demand-Satisfaction Ratio (MD-SR), sleep quality, work load (workday versus day off), at work (versus not being at the workplace), and lunch. The effect of time of day on cortisol was controlled for before the effects of these variables were determined. Momentary negative mood but not trait negative affect was positively associated with ambulatory measured cortisol. The variables from the work stress model--effort, reward, need for control, and the multiple occasion measurements of demand and satisfaction--did not affect cortisol. As could be expected, time of day had an effect on cortisol, but a hypothesised interaction with momentary negative mood was not found. Additionally, the results show that the time course of cortisol differs between individuals and that the effect of sleep quality on cortisol can vary from person to person. This points to the necessity of continued efforts to single out sources of individual variability. The finding that variables derived from the effort-reward imbalance model are not related with cortisol does not support the hypothesis that ERI leads to short-term changes in cortisol, indicating no relation with hypothalamic-pituitary-adrenal (HPA) axis activity. On the other hand, the present results invite further qualification of negative affect as a potential determinant of HPA activity, at least, as far as can be deduced from cortisol measurements.

Adult↗