Joint action of smoking and asbestos exposure on lung cancer

Our plain-English summary of Joint action of smoking and asbestos exposure on lung cancer, by F.D. Liddell (Occupational and Environmental Medicine, 2002).

The study

• Author: F.D. Liddell
• Journal: Occupational and Environmental Medicine
• Published: 2002;59(7):494-5; author reply 495-6
• Type of article: Comment, Letter
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Summary of the article

This letter commented on a 2001 review by P N Lee of how smoking and asbestos exposure act jointly on lung cancer risk, and it was published with Lee's reply. Lee had calculated V, the ratio of the asbestos relative risk in smokers to that in non-smokers, where V = 1 indicates a multiplicative interaction. His original weighted average for 16 results was 0.90 (95% CI 0.67 to 1.20). After acknowledged errors were corrected, V fell to 0.83 (95% CI 0.63 to 1.08). Values were 0.63 for cohort studies and 1.08 for case-referent studies, a difference with p = 0.049. Liddell argued for excluding four further results: two cohorts that broke the rule of independence, one showing no asbestos effect, and a Chinese cohort with low smoking risks. These exclusions gave a cohort V of 0.54 (95% CI 0.35 to 0.82) and a difference between study types with p = 0.017. He questioned the case-referent studies because of unreliable job histories, proxy reporting, impure definitions of non-smokers and exposure to other carcinogens. Further adjustments gave V = 0.47 (95% CI 0.29 to 0.75). He concluded that neither the multiplicative nor the additive hypothesis was generally satisfactory and that interaction takes several forms. Lee agreed with the corrections but found the exclusions unconvincing; with them, V for all studies was 0.79 (95% CI 0.59 to 1.05). He concluded that the asbestos relative risk may be somewhat lower in smokers, but that the data did not clearly reject the multiplicative relation.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This was a letter to the editor, not a new study. It was printed with a reply from P Lee. The letter's author commented on a 2001 review by Lee of studies on how asbestos exposure and cigarette smoking together affect lung cancer risk, comparing smokers with non-smokers. That review used a statistic, V, the ratio of the asbestos relative risk in smokers to that in non-smokers. V equals 1 if the two effects multiply. Lee's average was V = 0.90 (95% CI: 0.67 to 1.20). After agreed corrections it was 0.83 (95% CI: 0.63 to 1.08): 0.63 for nine cohort studies and 1.08 for nine case-referent studies (p = 0.049). The letter's author argued for excluding several studies and for relying on cohort studies. On that basis the cohort V was 0.54 (95% CI: 0.35 to 0.82), or 0.47 (95% CI: 0.29 to 0.75) with further changes. The author concluded that neither the multiplicative nor the additive hypothesis was generally satisfactory and that interaction takes several forms. In reply, Lee disputed the exclusions and concluded that the data did not clearly reject the multiplicative relation.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Letter to the editor commenting on and re-analysing a published review, with the review author's reply; no new data were collected
• Who was studied: Published studies included in Lee's 2001 review of lung cancer risk from asbestos and smoking: 16 results in the original analysis, then nine cohort and nine case-referent results after corrections
• Exposure: Asbestos exposure and cigarette smoking considered together, comparing the asbestos relative risk in smokers with that in non-smokers. Studies discussed included North American insulation workers exposed to chrysotile, crocidolite miners, Finnish anthophyllite asbestos miners and a Chinese asbestos factory cohort.
• Main results:
  • In Lee's original analysis of 16 results, the weighted average V was 0.90 (95% CI: 0.67 to 1.20).
  • After correcting one misquoted result and two incorrect omissions, V was 0.83 (95% CI: 0.63 to 1.08). It was 0.63 for nine cohorts and 1.08 for nine case-referent studies, a difference with p = 0.049.
  • After the letter's author excluded four studies, V for the cohort studies was 0.54 (95% CI: 0.35 to 0.82). The difference between study types was p = 0.017.
  • Discarding the North American insulation workers result and adding the crocidolite miners study gave V = 0.47 (95% CI: 0.29 to 0.75).
  • In the reply, Lee reported that with the four suggested exclusions, V for all studies combined was 0.79 (95% CI: 0.59 to 1.05).
  • In the reply, Lee reported that the difference between study types was no longer statistically significant (p = 0.089) if the estimate from one study showing a very low V was revised. Lee described this revision as itself questionable.
• The authors' conclusion: The letter's author concluded that the multiplicative hypothesis is not generally satisfactory, that the additive hypothesis is not either (though it fits some data sets very well), and that interaction takes several forms. In reply, Lee concluded that the asbestos relative risk may be somewhat lower in smokers than in non-smokers, but that the data do not clearly reject the simple multiplicative relation.
• Limitations the authors state:
  • The letter's author stated that the nature of the data imposes very large error. Analyses must also assume that exposed and unexposed people smoked equally, and that smokers and non-smokers were equally exposed.
  • The letter's author stated that case-referent studies had impure definitions of non-smokers and assessed exposure retrospectively.
  • The letter's author acknowledged some doubt about the best estimate of V from cohort studies.
  • In reply, Lee noted that prospective studies may not record changes in smoking after follow-up begins.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Lung Cancer, Relative Risk.

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• Association of cigarette smoking and asbestos exposure with location and histology of lung cancer — B.W. Lee, J.C. Wain, et al. (1998)
• Lung cancer mortality from exposure to chrysotile asbestos and smoking: a case-control study within a cohort in China — E. Yano, X. Wang, et al. (2010)
• Combined effect of asbestos exposure and tobacco smoking on Finnish anthophyllite miners and millers — L.O. Meurman, R. Kiviluoto, et al. (1979)
• The combination of effects on lung cancer of cigarette smoking and exposure in quebec chrysotile miners and millers — F.D. Liddell, B.G. Armstrong (2002)

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