Years of Life Lost due to exposure: Causal concepts and empirical shortcomings

Excess Years of Life Lost due to exposure is an important measure of health impact complementary to rate or risk statistics. I show that the total excess Years of Life Lost due to exposure can be estimated unbiasedly by calculating the corresponding excess Years of Potential Life Lost given conditions that describe study validity (like exchangeability of exposed and unexposed) and assuming that exposure is never preventive. I further demonstrate that the excess Years of Life Lost conditional on age at death cannot be estimated unbiasedly by a calculation of conditional excess Years of Potential Life Lost without adopting speculative causal models that cannot be tested empirically. Furthermore, I point out by example that the excess Years of Life Lost for a specific cause of death, like lung cancer, cannot be identified from epidemiologic data without assuming non-testable assumptions about the causal mechanism as to how exposure produces death. Hence, excess Years of Life Lost estimated from life tables or regression models, as presented by some authors for lung cancer or after stratification for age, are potentially biased. These points were already made by Robins and Greenland 1991 reasoning on an abstract level. In addition, I demonstrate by adequate life table examples designed to critically discuss the Years of Potential Life Lost analysis published by Park et al. 2002 that the potential biases involved may be fairly extreme. Although statistics conveying information about the advancement of disease onset are helpful in exposure impact analysis and especially worthwhile in exposure impact communication, I believe that attention should be drawn to the difficulties involved and that epidemiologists should always be aware of these conceptual limits of the Years of Potential Life Lost method when applying it as a regular tool in cohort analysis

Diesel exhaust in miners study: how to understand the findings?

Abstract The Diesel Exhaust in Miners Study (DEMS) is an outstanding epidemiological project on the association between occupational diesel exhaust exposures, measured as long-term respirable elemental carbon (REC) estimates, and lung cancer mortality in a large cohort of US miners. Two articles published recently (Attfield et al. (J Natl Cancer Inst Epub, 2012), Silverman et al. (J Natl Cancer Inst Epub, 2012)) dsescribed the epidemiological findings. These papers are expected to have considerable impact on the evaluation of the carcinogenic potential of diesel exhaust and, furthermore, on occupational and environmental limit value discussions related to diesel motor emissions and particle exposures. DEMS found remarkable exposure-response relationships between REC exposure estimates and lung cancer mortality - conditional on a pronounced effect of surface vs. underground work on lung cancer risk. If this risk factor is ignored the estimated REC-lung cancer association is attenuated substantially. The authors relied on this risk factor in their main analyses. However, this factor “surface/underground work” remained unexplained. The factor lead the authors to introduce unusual cross-product terms of location and smoking in adjustment procedures and even caused the authors to hypothesize that high REC exposures are protective against lung cancer excess risks due to smoking. To understand the reliability of these conclusions, we should ask basic questions about the data collection process in DEMS: Did the mortality follow-up procedures suffer from errors like those that affected the NCI formaldehyde cohort study? Are the REC and/or smoking data reliable, and are these data collected/constructed in such a way that the procedures allow valid comparisons between surface and underground workers? Without clarifying the issues raised in this Commentary the Diesel Exhaust in Miners Study remains to be difficult to interpret.</p

The impact of performance communication on process efficiency : a RPA implementation project

How can you use an effective and reproducible process to incentivise executives of one of Portugal's largest companies to prioritise a repetitive task? This question led to our main goal of the project, which is documented in the following and supported by fundamental literature research, how to design and implement effective performance-based communication through the technological mapping of Robotic Process Automation. The problem of the Master Thesis was brought to the author's attention by the research partnership of the Portuguese Postal Service CTT with the Catolica Lisbon School of Business and Economics and was attempted to be solved in an implementation project with the help of the already existing RPA capabilities of CTT. In a first step, the processes affected by the problem were documented and subsequently restructured with the help of the CTT project management framework in order to integrate them into the architecture of the organisation using the RPA technology. In order to solve the problem of incentivising higher prioritisation of the task, the nudging method of communication was identified. By applying this, personalised ranking-based notifications were sent to solve the problem. In summary, the underlying work should provide the reader with documentation to apply the described process in a replicable way to comparable problems.Como pode utilizar um processo eficaz e reprodutível para incentivar os executivos de uma das maiores empresas portuguesas a darem prioridade a uma tarefa repetitiva? Esta pergunta conduziu ao nosso principal objectivo do projecto, documentado no seguinte e apoiado por investigação bibliográfica fundamental, como conceber e implementar uma comunicação eficaz baseada no desempenho através do mapeamento tecnológico da Automação de Processos Robóticos. O problema da tese de mestrado foi trazido à atenção do autor pela parceria de investigação do Serviço Postal Português CTT com a Escola de Negócios e Economia Católica de Lisboa e foi tentado ser resolvido num projecto de implementação com a ajuda das capacidades de RPA já existentes dos CTT. Numa primeira fase, os processos afectados pelo problema foram documentados e subsequentemente reestruturados com a ajuda do quadro de gestão do projecto dos CTT, a fim de os integrar na arquitectura da organização utilizando a tecnologia RPA. A fim de resolver o problema de incentivar a atribuição de maior prioridade à tarefa, foi identificado o método de comunicação de incentivo. Ao aplicar este método, foram enviadas notificações personalizadas baseadas na classificação para resolver o problema. Em resumo, o trabalho subjacente deveria fornecer ao leitor documentação para aplicar o processo descrito de uma forma replicável a problemas comparáveis

Gefährdungsbeurteilung bei Exposition gegenüber mehreren krebserzeugenden Arbeitsstoffen

We analyzed the validity of simple summation formulae with which a common effect of different occupational exposures could be mapped to the same cancer endpoint. Our paper published in this journal relied on the assumptions of a deterministic response and binary exposures. The German Federal Environmental Agency organized an external review of our paper. Although the reviewers agreed with our main conclusion that simple summation formulae cannot have a general validity, they raised questions that we would like to inform the scientific public about and are addressed in this addendum. We demonstrate that the main statements in Morfeld and Spallek 2015 remain valid even if the exposures are defined on an interval scale, the binary response is probabilistic or if the analyzed response types are restricted to adverse types. We clarify that excess risks and differences in excess risks are not probabilities according to the Kolmogorov axioms. Simple summation formulae are therefore not justified, not even to estimate the lower bounds for excess risks

Bayesian bias adjustments of the lung cancer SMR in a cohort of German carbon black production workers

<p>Abstract</p> <p>Background</p> <p>A German cohort study on 1,528 carbon black production workers estimated an elevated lung cancer SMR ranging from 1.8-2.2 depending on the reference population. No positive trends with carbon black exposures were noted in the analyses. A nested case control study, however, identified smoking and previous exposures to known carcinogens, such as crystalline silica, received prior to work in the carbon black industry as important risk factors.</p> <p>We used a Bayesian procedure to adjust the SMR, based on a prior of seven independent parameter distributions describing smoking behaviour and crystalline silica dust exposure (as indicator of a group of correlated carcinogen exposures received previously) in the cohort and population as well as the strength of the relationship of these factors with lung cancer mortality. We implemented the approach by Markov Chain Monte Carlo Methods (MCMC) programmed in R, a statistical computing system freely available on the internet, and we provide the program code.</p> <p>Results</p> <p>When putting a flat prior to the SMR a Markov chain of length 1,000,000 returned a median posterior SMR estimate (that is, the adjusted SMR) in the range between 1.32 (95% posterior interval: 0.7, 2.1) and 1.00 (0.2, 3.3) depending on the method of assessing previous exposures.</p> <p>Conclusions</p> <p>Bayesian bias adjustment is an excellent tool to effectively combine data about confounders from different sources. The usually calculated lung cancer SMR statistic in a cohort of carbon black workers overestimated effect and precision when compared with the Bayesian results. Quantitative bias adjustment should become a regular tool in occupational epidemiology to address narrative discussions of potential distortions.</p

The assessment of mood at workplace - psychometric analyses of the revised Profile of Mood States (POMS) questionnaire

With the Profile of Mood States (POMS), a German version of an international instrument for the assessment of mood is available. The paper introduces a new short version containing 24 items and four scales. In a study about indoor climate in 4596 office workers only a few missing values were noted. Psychometric analyses showed very good characteristics of the four scales regarding their internal consistency (Cronbach’s α) and scale fit. High floor effects indicated a limited exhaustion of the scale range. Age and gender effects of the scale scores concerned the scales “vigour” and “fatigue”. Furthermore, the scales of the POMS discriminated between groups with different self-reported disease incidences. A less beneficial characteristic of the POMS could be noted in terms of a high correlation of the scales “numbness” and “fatigue". With the tested version of the POMS, a short instrument with good psychometric properties has been presented which can be assessed in healthy as well as in health-impaired persons

Response to the Reply on behalf of the ‘Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area’ (MAK Commission) by Andrea Hartwig Karlsruhe Institute of Technology (KIT)

Prof. Hartwig commented [1] as chair of the MAK Commission on Morfeld et al. 2015 [2]. We would like to thank the Commission for commenting on our review. However, the MAK Commission did not address a number of important issues raised in our paper