Downloaded from http://oem.bmj.com/ on June 21, 2015 - Published by group.bmj.com
PostScript
LETTERS
Is there a lung cancer risk in US coal miners? Recently, the 37-years follow-up of the US coal miners’ cohort was published in this journal.1 We would like to comment on the presentation and interpretation of this study, especially on the lung cancer results. First, the non-significant lung cancer standardised mortality ratio (SMR) does not differ from the SMR after the 23-year follow-up.2 Even the SMRs of the five regions were similar between both follow-ups. Emphasising a ‘significant’ relationship with lung cancer mortality in the abstract seems to be inappropriate in view of borderline results, lacking exposure-response relationship and nonsignificant results of the categorical analysis. Second, SMRs between regions differ considerably, especially those for lung cancer—significantly up to a factor of 3. We would suggest using regional rates for each region and then combining results to avoid bias. Third, what is the justification for using West as reference—the region with a significantly and by more than 50% reduced SMR? This may lead to high HR for the other regions. Also, table 4 of Graber et al presented the lung cancer HR. For coal mine dust and silica exposure the mean cumulative exposures were used (64.6 mg/m3-years and 2.6 mg/m3-years, respectively). Usually, an increase of one unit (here 1 mg/m3-years) is used for continuous variables. This would lead to much lower risk estimates of log cumulative coal mine dust (HR=1.14) and cumulative respirable silica (HR=1.02), as calculated by us. Then, the quantitative exposure-response data are obviously based on the assumptions that jobs of the miners and the level of exposure have not changed after study enrolment. The complete cumulative exposure data are based on some measurements collected during environmental surveys at certain US mines by the Bureau of Mines between 1968 and 1969. It is unclear how these unrealistic assumptions and the selective cross-sectional measurement data may have biased the risk estimates. Lastly, we notice that some of the confidence limits are erroneous, for example, on page 30: HR=1.33 (95% CI 0.94 to 1.33), HR=1.04 (95% CI 0.96 to 1.52), on page 35: HR=1.13 (95% CI 0.95 to 1.92), on page 37: HR=1.04 (95% CI Occup Environ Med July 2014 Vol 71 No 7
0.94 to 1.94) and in Table 3: HR=1.32 (95% CI 1.01 to 1.57). Dirk Taeger, Olaf Hagemeyer, Rolf Merget, Thomas Brüning, Dirk Pallapies Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the Ruhr-Universität Bochum (IPA), Bochum, Germany Correspondence to Dr Dirk Taeger, Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the RuhrUniversität Bochum (IPA), Buerkle-de-la-Camp-Platz 1, Bochum 44789, Germany; [email protected] Contributors None. Competing interests None. Provenance and peer review Not commissioned; externally peer reviewed.
To cite Taeger D, Hagemeyer O, Merget R, et al. Occup Environ Med 2014;71:523. Received 6 February 2014 Revised 28 February 2014 Accepted 9 March 2014 Published Online First 27 March 2014
▸ http://dx.doi.org/10.1136/oemed-2013-101597 Occup Environ Med 2014;71:523. doi:10.1136/oemed-2014-102146
REFERENCES 1
2
Graber JM, Stayner LT, Cohen RA, et al. Respiratory disease mortality among US coal miners; results after 37 years of follow-up. Occup Environ Med 2014;71:30–9. Attfield MD, Kuempel ED. Mortality among U.S. underground coal miners: a 23-year follow-up. Am J Ind Med 2008;51:231–45.
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Downloaded from http://oem.bmj.com/ on June 21, 2015 - Published by group.bmj.com
Is there a lung cancer risk in US coal miners? Dirk Taeger, Olaf Hagemeyer, Rolf Merget, Thomas Brüning and Dirk Pallapies Occup Environ Med 2014 71: 523 originally published online March 28, 2014
doi: 10.1136/oemed-2014-102146 Updated information and services can be found at: http://oem.bmj.com/content/71/7/523.1
These include:
References Email alerting service
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Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
PostScript
LETTERS
Is there a lung cancer risk in US coal miners? Recently, the 37-years follow-up of the US coal miners’ cohort was published in this journal.1 We would like to comment on the presentation and interpretation of this study, especially on the lung cancer results. First, the non-significant lung cancer standardised mortality ratio (SMR) does not differ from the SMR after the 23-year follow-up.2 Even the SMRs of the five regions were similar between both follow-ups. Emphasising a ‘significant’ relationship with lung cancer mortality in the abstract seems to be inappropriate in view of borderline results, lacking exposure-response relationship and nonsignificant results of the categorical analysis. Second, SMRs between regions differ considerably, especially those for lung cancer—significantly up to a factor of 3. We would suggest using regional rates for each region and then combining results to avoid bias. Third, what is the justification for using West as reference—the region with a significantly and by more than 50% reduced SMR? This may lead to high HR for the other regions. Also, table 4 of Graber et al presented the lung cancer HR. For coal mine dust and silica exposure the mean cumulative exposures were used (64.6 mg/m3-years and 2.6 mg/m3-years, respectively). Usually, an increase of one unit (here 1 mg/m3-years) is used for continuous variables. This would lead to much lower risk estimates of log cumulative coal mine dust (HR=1.14) and cumulative respirable silica (HR=1.02), as calculated by us. Then, the quantitative exposure-response data are obviously based on the assumptions that jobs of the miners and the level of exposure have not changed after study enrolment. The complete cumulative exposure data are based on some measurements collected during environmental surveys at certain US mines by the Bureau of Mines between 1968 and 1969. It is unclear how these unrealistic assumptions and the selective cross-sectional measurement data may have biased the risk estimates. Lastly, we notice that some of the confidence limits are erroneous, for example, on page 30: HR=1.33 (95% CI 0.94 to 1.33), HR=1.04 (95% CI 0.96 to 1.52), on page 35: HR=1.13 (95% CI 0.95 to 1.92), on page 37: HR=1.04 (95% CI Occup Environ Med July 2014 Vol 71 No 7
0.94 to 1.94) and in Table 3: HR=1.32 (95% CI 1.01 to 1.57). Dirk Taeger, Olaf Hagemeyer, Rolf Merget, Thomas Brüning, Dirk Pallapies Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the Ruhr-Universität Bochum (IPA), Bochum, Germany Correspondence to Dr Dirk Taeger, Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the RuhrUniversität Bochum (IPA), Buerkle-de-la-Camp-Platz 1, Bochum 44789, Germany; [email protected] Contributors None. Competing interests None. Provenance and peer review Not commissioned; externally peer reviewed.
To cite Taeger D, Hagemeyer O, Merget R, et al. Occup Environ Med 2014;71:523. Received 6 February 2014 Revised 28 February 2014 Accepted 9 March 2014 Published Online First 27 March 2014
▸ http://dx.doi.org/10.1136/oemed-2013-101597 Occup Environ Med 2014;71:523. doi:10.1136/oemed-2014-102146
REFERENCES 1
2
Graber JM, Stayner LT, Cohen RA, et al. Respiratory disease mortality among US coal miners; results after 37 years of follow-up. Occup Environ Med 2014;71:30–9. Attfield MD, Kuempel ED. Mortality among U.S. underground coal miners: a 23-year follow-up. Am J Ind Med 2008;51:231–45.
523
Downloaded from http://oem.bmj.com/ on June 21, 2015 - Published by group.bmj.com
Is there a lung cancer risk in US coal miners? Dirk Taeger, Olaf Hagemeyer, Rolf Merget, Thomas Brüning and Dirk Pallapies Occup Environ Med 2014 71: 523 originally published online March 28, 2014
doi: 10.1136/oemed-2014-102146 Updated information and services can be found at: http://oem.bmj.com/content/71/7/523.1
These include:
References Email alerting service
This article cites 2 articles, 1 of which you can access for free at: http://oem.bmj.com/content/71/7/523.1#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
