Occupational asbestos exposure as a risk factor for laryngeal carcinoma in a population-based case-control study from Germany

Our plain-English summary of Occupational asbestos exposure as a risk factor for laryngeal carcinoma in a population-based case-control study from Germany, by H. Ramroth, W. Ahrens, A. Dietz, et al (American Journal of Industrial Medicine, 2011).

The study

• Authors: H. Ramroth, W. Ahrens, A. Dietz, H. Becher
• Journal: American Journal of Industrial Medicine
• Published: 2011;54(7):510-4
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: As several studies have identified asbestos exposure as an independent occupational risk factor for laryngeal cancer, the aim of our study was to confirm this association.

Methods: In a population-based case-control study on laryngeal cancer in South-West Germany occupational exposures and other risk factors were obtained by face-to-face interviews using a detailed standardized questionnaire covering the complete individual working history, supplemented by job-specific questionnaires (JSQ) especially for selected jobs known to entail exposure to asbestos. Detailed exposure information was collected over a wide range of asbestos related jobs and branches and analyzed using different modeling strategies.

Results: Seventy-three (28.4%) cases and 158 (20.5%) controls reported any exposure to asbestos. Elevated risk estimates for asbestos exposure were found. However, those became substantially reduced after adjustment for smoking and alcohol.

Conclusion: Moderately elevated risks for laryngeal cancer after exposure to asbestos were confirmed. Difficulties in the collection of adequate exposure data were demonstrated.

Copyright © 2011 Wiley-Liss, Inc.

In plain English

This brief report described a population-based case-control study of laryngeal (voice box) cancer in South-West Germany. The authors interviewed 257 people with laryngeal cancer, recruited 1998 to 2000, about their working lives. They also interviewed population controls, frequency-matched 1:3 for age and sex. The article did not name asbestos fiber types. Any asbestos exposure was reported by 73 cases (28.4%) and 158 controls (20.5%). Before adjustment, the odds ratio for any exposure was 1.5 (95% CI 1.1 to 2.1). After adjustment for smoking and alcohol it fell to 1.2 (95% CI 0.83 to 1.7), and no main estimate was statistically significant. By lifelong hours of any exposure, only the middle band (940 to 5,280 hours) stayed elevated after adjustment (1.9, 95% CI 1.1 to 3.4). The highest band did not (0.89, 95% CI 0.49 to 1.6), and the trend test was not significant (p = 0.4291). Allowing for latency of up to 20 years changed nothing. The authors concluded that moderately elevated risks were confirmed and that collecting adequate exposure data was difficult. They noted the study was too small for detailed analyses.

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: Population-based case-control study (published as a brief report)
• Who was studied: 257 histologically confirmed laryngeal cancer cases (236 males, 21 females; response rate 89.2%) were recruited 1998 to 2000 in a region of about 2.7 million people in South-West Germany (Heidelberg, Mannheim, Ludwigshafen, Darmstadt, Heilbronn). Population controls were randomly selected from population registries and frequency-matched 1:3 for age and sex (response rate 62.4%). The article does not state the total number of controls. The male and female control counts in Table I (702 and 67) add up to 769.
• Exposure: Occupational asbestos exposure over the whole working life, assessed by face-to-face interviews with job-specific questionnaires (JSQ) and a substance checklist (SCL). Jobs covered included roofer, insulation installer, pipe layer, welder, auto mechanic, plumber and docker, plus asbestos processing and textile industries. Exposure was summarized as lifelong working hours, overall and for asbestos processing, isolation, heat protection, and handling of asbestos material. Cut points were 0, 940 and 5,280 hours. No fiber types were specified.
• Main results:
  • Any asbestos exposure (JSQ or SCL) was reported by 73 of 257 cases (28.4%) and 158 controls (20.5%).
  • Any exposure (JSQ or SCL): crude OR 1.5 (95% CI 1.1 to 2.1). Adjusted for smoking and alcohol: OR 1.2 (95% CI 0.83 to 1.7).
  • JSQ exposure: crude OR 1.8 (95% CI 1.2 to 2.5). SCL exposure: crude OR 1.3 (95% CI 0.9 to 2.0).
  • After adjustment for smoking and alcohol, the elevated crude estimates were substantially reduced and none remained statistically significant. Adjusted values were JSQ OR 1.2 (95% CI 0.84 to 1.9) and SCL OR 1.0 (95% CI 0.67 to 1.6).
  • Agreement between the two exposure methods was moderate (Kappa 0.51 for cases, 0.48 for controls).
  • By lifelong working hours of any exposure (JSQ or SCL), the 940 to 5,280 hour group had an adjusted OR of 1.9 (95% CI 1.1 to 3.4). This group comprised 33 cases (12.8%) and 44 controls (5.7%).
  • The over 5,280 hour group for any exposure had an adjusted OR of 0.89 (95% CI 0.49 to 1.6). The p-value for trend was 0.4291.
  • Excluding exposures from the last 5, 10, 15 or 20 years before interview, to allow for latency, did not change the results.
  • Separate analyses of laryngeal sub-sites (glottic/subglottic and supraglottic) found no relevant effect.
  • Additional adjustment for cement dust and wood dust exposure left results unchanged.
• The authors' conclusion: The authors concluded that moderately elevated risks for laryngeal cancer after asbestos exposure were confirmed, and that their study demonstrated difficulties in collecting adequate exposure data.
• Limitations the authors state:
  • The study size seemed too small for detailed analyses, and was limited for the sub-site analyses.
  • No measurements of non-occupational, environmental asbestos exposure were available, so some confounding might be plausible.
  • Recall bias cannot be completely ruled out. The authors saw no indication of differential recall and thought some bias toward the null was possible.
  • The substance checklist may be less reliable than job-specific questions, because participants may not have known they were exposed to asbestos.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Carcinoma, Case-Control Study, Laryngeal Cancer, Occupational Exposure.

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