232 e-Letters

  • Analysis of job strain effects
    Sigurd Mikkelsen

    Fujishiro et al.1 recently published data on the association of job demands and control with carotid artery intima-media thickness (IMT). The joined effect of demands and control (strain) was analyzed by five different strain definitions: 1. a quadrant term (median splits of demands and control), 2. combinations of tertiles of demands and control, 3. an additive term (demands minus control) , 4. a quotient term (the ra...

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  • Cancer risks in a historical UK cohort of benzene exposed workers
    Jeremy Beach

    Dear Editor

    We read with interest the article by Sorahan et al., “Cancer risks in a historical UK cohort of benzene exposed workers” [1]. We note that the authors showed an increased SMR and SRR for lung cancer among this group. They comment that “there was evidence of increased mortality for lung and lip cancers and for ANLL, and increased morbidity for lung and pleural cancers. There is no reason to suspect that benze...

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  • Exposure to keyboard/mouse use = keystrokes + mouse clicks + POSTURE - a missing variable that cannot be overstated
    Margit L. Bleecker

    Self-report of duration of computer use is usually overestimated. The search for a valid measure of exposure to keyboard/mouse use resulted in the development of a computer registration software. The use of this new software generated unexpected results when IJmker et al.1 found software- recorded computer use was not significantly associated with upper extremity/neck symptom onset while self-reported computer use was sig...

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  • Dust exposure and cardiovascular morbidity
    Bengt Sjögren

    Dear Editor,

    We have read the study on respiratory disease and cardiovascular morbidity by Koskela and coworkers with great interest.[1] They found no obvious effect of direct dust exposure on ischaemic heart disease (IHD) among granite workers and workers in metal industry such as foundry workers and iron foundry workers in Finland. Furthermore, there was a weak association between dust exposure and chronic bronc...

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  • Re:Analysis of job strain effects
    Kaori Fujishiro

    We thank Dr. Mikkelsen and colleagues for their constructive comments on our paper. Our responses to their three major questions are listed below.

    1) Why did we present various formulations of job strain?

    The five formulations of job strain have been commonly reported in the literature. Often, authors chose one or two formulations and thus would not know if their results were consistent across differe...

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  • Air samples versus biomarkers for epidemiology: not so straightforward
    Hans Kromhout

    Dear Editor,

    Sir, the recent paper by Lin et al.[1] in the November issue of the journal was a thought provoking piece of work. In their paper the authors try to prove the theoretically derived hypothesis that biomarkers of exposure have smaller variance ratios and would typically provide less biased surrogates of exposure compared to air measurements. Although I entirely agree with the theoretical part of this s...

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  • Does self-reported computer work add biologically relevant information beyond that of objectively recorded computer work?
    Sigurd Mikkelsen

    In a recent editorial Gerr et al.[1] discuss computer work and musculoskeletal outcomes based on self-reported exposure versus objective recordings using computer software. They state that only one small study (n=27) using objective recordings was published before a large study by Ijmker et al.[2], published in the same issue as the editorial. They failed to consider the results of two NUDATA papers based on more than 2...

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  • Authors' response to Kromhout
    S.M. Rappaport, Ph.D.

    The Editor,

    We appreciate Dr. Kromhout’s comments regarding our article “Air samples versus biomarkers for epidemiology”[1] and are pleased that he supports our recommendation that both air samples and biomarkers be collected whenever possible. Kromhout raises three points in his letter. First, he suggests that our conclusion that biomarkers tend to be better surrogates for exposures than air samples might have b...

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  • Response to "Does self-reported computer work add biologically relevant information beyond that of objectively recorded computer work?"
    Fred Gerr

    We appreciate the careful reading of our editorial [1] by Drs. Mikkelsen and Andersen. We regret our omission of the one published NUDATA study available at the time our editorial was submitted [2]. That study reported significant associations between mouse usage time collected with memory resident software and both, acute neck pain and acute shoulder pain, among 2146 technical assistants. However, because i) median mouse...

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  • Comments on modelling longitudinal ordinal data
    Anna E Ekman

    Dear Editor,

    This article is presenting both the applied question and the statistical methods used in a very well organised and excellent way. Though, I have some comments on the use of the words risk, effect and predictor as these imply a casual relationship and make us believe that we model the development of neck pain.

    The data in the article is longitudinal and in the analysis the authors are using this...

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