Jean-Baptist du Prel

Are meteorological parameters associated with acute respiratory tract infections

BACKGROUND Information on the onset of epidemics of acute respiratory tract infections (ARIs) is useful in timing preventive strategies (eg, the passive immunization of high-risk infants against respiratory syncytial virus [RSV]). Aiming at better predictions of the seasonal activity of ARI pathogens, we investigated the influence of climate on hospitalizations for ARIs. METHODS Samples obtained from 3044 children hospitalized with ARIs in Mainz, Germany, were tested for pathogens with a multiplex reverse-transcriptase polymerase chain reaction enzyme-linked immunosorbent assay from 2001 through 2006. Hospitalizations for ARIs were correlated with meteorological parameters recorded at the University of Mainz. The frequency of hospitalization for RSV infection was predicted on the basis of multiple time series analysis. RESULTS Influenza A, RSV, and adenovirus were correlated with temperature and rhinovirus to relative humidity. In a time series model that included seasonal and climatic conditions, RSV-associated hospitalizations were predictable. CONCLUSIONS Seasonality of certain ARI pathogens can be explained by meteorological influences. The model presented herein is a first step toward predicting annual RSV epidemics using weather forecast data.

Confidence Interval or P-Value?: Part 4 of a Series on Evaluation of Scientific Publications

BACKGROUND An understanding of p-values and confidence intervals is necessary for the evaluation of scientific articles. This article will inform the reader of the meaning and interpretation of these two statistical concepts. METHODS The uses of these two statistical concepts and the differences between them are discussed on the basis of a selective literature search concerning the methods employed in scientific articles. RESULTS/CONCLUSIONS P-values in scientific studies are used to determine whether a null hypothesis formulated before the performance of the study is to be accepted or rejected. In exploratory studies, p-values enable the recognition of any statistically noteworthy findings. Confidence intervals provide information about a range in which the true value lies with a certain degree of probability, as well as about the direction and strength of the demonstrated effect. This enables conclusions to be drawn about the statistical plausibility and clinical relevance of the study findings. It is often useful for both statistical measures to be reported in scientific articles, because they provide complementary types of information.

Sample Size Calculation in Clinical Trials: Part 13 of a Series on Evaluation of Scientific Publications

BACKGROUND In this article, we discuss the purpose of sample size calculation in clinical trials, the need for it, and the methods by which it is accomplished. Study samples that are either too small or too large are unacceptable, for clinical, methodological, and ethical reasons. The physicians participating in clinical trials should be directly involved in sample size planning, because their expertise and knowledge of the literature are indispensable. METHODS We explain the process of sample size calculation on the basis of articles retrieved by a selective search of the international literature, as well as our own experience. RESULTS We present a fictitious clinical trial in which two antihypertensive agents are to be compared to each other with a t-test and then show how the appropriate size of the study sample should be calculated. Next, we describe the general principles of sample size calculation that apply when any kind of statistical test is to be used. We give further illustrative examples and explain what types of expert medical knowledge and assumptions are needed to calculate the appropriate sample size for each. These generally depend on the particular statistical test that is to be performed. CONCLUSION In any clinical trial, the sample size has to be planned on a justifiable, rational basis. The purpose of sample size calculation is to determine the optimal number of participants (patients) to be included in the trial. Sample size calculation requires the collaboration of experienced biostatisticians and physician-researchers: expert medical knowledge is an essential part of it.

Choosing Statistical Tests: Part 12 of a Series on Evaluation of Scientific Publications

BACKGROUND The interpretation of scientific articles often requires an understanding of the methods of inferential statistics. This article informs the reader about frequently used statistical tests and their correct application. METHODS The most commonly used statistical tests were identified through a selective literature search on the methodology of medical research publications. These tests are discussed in this article, along with a selection of other standard methods of inferential statistics. RESULTS AND CONCLUSIONS Readers who are acquainted not just with descriptive methods, but also with Pearsons chi-square test, Fishers exact test, and Students t test will be able to interpret a large proportion of medical research articles. Criteria are presented for choosing the proper statistical test to be used out of the most frequently applied tests. An algorithm and a table are provided to facilitate the selection of the appropriate test.

Are effort-reward imbalance and social isolation mediating the association between education and depressiveness? Baseline findings from the lidA § -study

ObjectivesTo investigate multiple mediations of the association between education and depressive symptoms (BDI-V) by work-related stress (ERI) and social isolation, the regional variation of the first mediation and a potential moderating effect of regional unemployment rate.Methods6339 employees born in 1959 and 1965 were randomly recruited from 222 sample points in a German cohort study on work, age, health and work participation. A multilevel model of moderated lower-level mediation was used to investigate the confirmatory research question. Multiple mediations were tested corresponding to Baron and Kenny. These analyses were stratified for age and adjusted for sex, negative affectivity and overcommitment.ResultsIn the association between education and depressive symptoms, indirect effects of work-related stress and social isolation were significant in both age cohorts whereas a direct association was observable in the younger cohort, only. The significant regional variation in the association between work-related stress and depressive symptoms was not statistically explained by regional unemployment rate.ConclusionsOur findings point out that work-related stress and social isolation play an intermediary role between education and depressive symptoms in middle-aged employees.

Are status inconsistency, work stress and work-family conflict associated with depressive symptoms? Testing prospective evidence in the lidA study

BACKGROUND Depressive symptoms are common and economically relevant. Women suffer more often than men do. We analyze associations between social status inconsistency, psychosocial factors, and depressive symptoms stratified by gender. METHODS In the present study, 3340 employees of two age cohorts (1959, 1965) working in two waves (2011, 2014) of the prospective German lidA-study and who gave written consent to link register data regarding their employment histories were included. Gender-specific influences of social status inconsistency (deviation of observed income from expected average income based on acquired education) on depressive symptoms and mediation of these associations by work stress in terms of effort-reward-imbalance (ERI) and work-family-conflict (WFC) were analyzed with confirmatory cross-lagged path models. RESULTS Among men, consistent status (i.e., average income in a specific educational group) increased the frequency of depressive symptoms. No association between negative SSI (i.e., income below the average income given a specific educational attainment) or positive SSI (i.e., income above the average income given a specific educational attainment) and depressive symptoms was observed among men or women. ERI and WFC were longitudinally associated with the outcome and differed slightly regarding gender, i.e., showing stronger effects of ERI for women and of WFC for men. Mediation of the association between social status and depressive symptoms was observed for men and for consistent status (path: consistent status → ERI → depressive symptoms) but not for SSI. CONCLUSIONS ERI and WFC increase the risk of future episodes with depressive symptoms in men and in women irrespective of SSI, occupational position, full- or part-time work, regional factors or individual characteristics.

Osteosynthesis of Proximal Humeral Fractures with the Fixed Angle PHILOS-plate

In a retrospective study we analyzed the functional and radiological outcome of 30 proximal humeral fractures, treated by PHILOS-plate, a fixed-angle device. Two of them were characterized as type Neer III, 14 as type Neer IV, 5 as type Neer V and 9 as type Neer VI. There were 2 2-part, 16 3-part and 12 4-part fractures. According to the constant-score, the normalized constant-score and the UCLA-score, good to excellent results were obtained in 66.7, 76.7 and 76.7%. Twenty-six (86.7%) patients had no or mild pain. Active forward flexion and active abduction over 90° was possible in 26 (86.7%) cases. Four (13.3%) patients developed partial avascular necrosis. Screw perforation was seen in 3 (10%) cases, delayed union in 1 (3.3%) case, malunion in 1 case and a loosening of plate and screws in another one. A secondary varus displacement of 5°–35° with a mean of 7° was found in 19 (63.3%) cases. The average time to union was 75 days. Fixation with PHILOS-plate is an adequate treatment for displaced 2- to 4-part fractures. Even in dislocated or 4-part fractures or in patients over 65 years good to excellent results were seen in the majority of cases.

Berufliche Gratifikationskrisen und Arbeitsunfähigkeit in Deutschland

ZusammenfassungHintergrundDer demografische Wandel geht in Industrienationen mit abnehmendem Arbeitskräfteangebot und alternden Belegschaften einher. Arbeitsunfähigkeit kann zu einem zusätzlichen Arbeitskräfteverlust führen. Zunehmende Krankmeldungen aufgrund psychischer Einschränkungen werfen Fragen zum Zusammenhang zwischen Arbeitsstress und Arbeitsunfähigkeit auf. Studien dazu sind gerade bei älteren Arbeitnehmern selten.ZielUntersucht wird der Einfluss von arbeitsbezogenem Stress aufgrund eines Ungleichgewichts zwischen beruflicher Verausgabung und dafür empfangener Belohnungen (Effort-Reward-Imbalance(ERI)-Modell) auf Arbeitsunfähigkeit bzw. Langzeitarbeitsunfähigkeit.Material und MethodenlidA („leben in der Arbeit“) ist eine deutschlandweite Kohortenstudie zu Arbeit, Alter, Gesundheit und Erwerbsteilhabe. 6339 repräsentative, sozialversicherungspflichtig Beschäftigte der Jahrgänge 1959 und 1965 wurden eingeschlossen. Die Teilnahmequote lag bei 27,3 % mit hoher Repräsentativität und ohne Selektivität der Stichprobe in 16 soziodemografischen Variablen. Arbeitsunfähigkeit war definitionsgemäß mindestens ein Fehltag, Langzeitarbeitsunfähigkeit mindestens 43 Fehltage in den letzten 12 Monaten. Arbeitsbezogener Stress wurde mit ERI-Terzilen parametrisiert. In der multiplen logistischen Regression wurde für Alter, Geschlecht, psychische Störungen, sozioökonomischen Status und Arbeitszeit adjustiert.ErgebnisseHochgradiger arbeitsbezogener Stress war bei älteren Beschäftigten unabhängig von Kovariaten mit Arbeitsunfähigkeit und Langzeitarbeitsunfähigkeit verbunden.DiskussionDer für Deutschland erstmals beobachtete Zusammenhang zwischen ERI und Arbeitsunfähigkeit stimmt mit den diesbezüglichen Ergebnissen der Mehrzahl internationaler Studien überein. Arbeitsstressreduktion könnte helfen, Arbeitskraft zu erhalten.AbstractBackgroundDemographic change is leading to a shrinking and ageing workforce in industrialized nations. Therefore, sickness absence may become a relevant problem. Increasing absenteeism and retirement rates due to mental disorders raise the question of an association between work-related stress and sickness absence. Studies on this matter, particularly in older employees, are rare.ObjectivesWe studied for the first time in Germany the relationship between effort–reward imbalance (ERI) and overall or long-term sickness absence.Materials and methodsLidA ( “Living at Work”) is a German cohort study on work, age, health, and work participation. A total of 6,339 employees born in 1959 and 1965 who were subject to social insurance contributions were interviewed nationwide using a representative sample concept. The response rate was 27.3 %. The sample showed high representativeness and no selectivity relating to 16 sociodemographic items. Sickness absence was defined as at least one long-term sickness absence with at least 43 days of absenteeism. Work-related stress was parameterized by ERI tertiles. Multiple logistic regression adjusting for age, sex, mental disorders, social status, and working time was performed.ResultsHigh levels of work-related stress were significantly associated with overall and long-term sickness absence among older employees after adjusting for covariates.ConclusionsOur unique findings on work-related stress and sickness absence in Germany are in agreement with the results of most international studies. Reducing work-related stress could help to preserve the workforce.

Work overcommitment: Is it a trait or a state?

PurposeEffort–reward imbalance (ERI) is a well-tested work-related stress model with three components, the two extrinsic components “efforts” and “rewards” and the one intrinsic component “overcommitment”. While an imbalance between “efforts” and “rewards” leads to strain reactions, “work-related overcommitment” (OC) has been described as a personal characteristic with a set of attitudes, behaviours, and emotions reflecting excessive striving combined with a strong desire for approval. However, the question whether OC is a personality trait or a response pattern sensitive to changes in the work context (state) is still open.Methods2940 Swedish industrial employees were included in this longitudinal analysis of the WOLF-Norrland data over 5 years. A change of OC index or its subscales were regressed against a change of freedom of choice at work, extra work, and ERI adjusted for age, sex, and education.ResultsWhile OC was insensitive to changes in freedom of choice at work and extra work, it was clearly associated with changes of work-related stress over time. Three of four OC subscales exhibited statistically significant associations with ERI.ConclusionsFor the first time, we studied fundamental characteristics of OC as an independent personality variable (trait) or an outcome variable subject to changes in the work environment (state). The association between external ERI and OC over time supports our hypothesis of OC being a state. Further investigations are needed to establish OC as a trait or a state.

Cut-off values for the applied version of the Beck Depression Inventory in a general working population

BackgroundThe Beck Depression Inventory (BDI) for the assessment of depressive symptoms is well established in clinical settings. An applied version (BDI-V) was previously developed in German for use within epidemiologic studies. The current study analyses the association between this applied version of the BDI and different measures of functioning. The aim is to determine BDI-V cut-off values when used in a population of employees.MethodsThe study included 6339 employees of the first wave of a German cohort study on work, age, health and work participation. Depressive symptoms were assessed by an applied version of the BDI-V. Data on functioning were obtained from personal interviews. The determination of cut-off values is achieved with the min-max principle for classification applied to receiver operating characteristic (ROC) curves.ResultsThe min-max principle points to a BDI-V cut-off between 20 and 24 for male and between 23 and 28 for female respondents. The corresponding sensitivities range between 0.64 and 0.75 for males and between 0.59 and 0.74 for females. Specificities range between 0.64 and 0.75 for males and between 0.60 and 0.74 for females. Female respondents have higher BDI-V cut-offs for all criteria.ConclusionsThe range of values is lower than a recommendation in a former study. In addition to this, the values differ for gender. The current analyses focus on an easier-to-use version of the BDI formerly applied for epidemiologic studies. The determination of cut-off values is based on criteria which are indicators for impairment in (work) functioning in a population of employees. Therefore, grouping of individuals according to the reported cut-off values is guided by the relevance of these scores for occupational functioning.