A case-control study of occupational risk factors for laryngeal cancer

Our plain-English summary of A case-control study of occupational risk factors for laryngeal cancer, by P. Wortley, T.L. Vaughan, S. Davis, et al (British Journal of Industrial Medicine, 1992).

The study

• Authors: P. Wortley, T.L. Vaughan, S. Davis, M.S. Morgan, D.B. Thomas
• Journal: British Journal of Industrial Medicine
• Published: 1992;49(12):837-44
• Cited by: 55 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

To determine whether specific jobs and occupational exposures are associated with laryngeal cancer lifetime occupational histories from a population-based case-control study in western Washington were examined. The study included 235 cases diagnosed between September 1983 and February 1987, and 547 controls identified by random digit dialing. After controlling for alcohol use, cigarette smoking, age and education, significantly increased risks were found for painters in construction (odds ratio (OR)) = 2.8, (95% confidence interval (95% CI) 1.1-6.9), supervisors and miscellaneous mechanics (OR = 2.3, 95% CI 1.1-4.8), construction workers (OR = 3.4, 95% CI 1.4-8.1), metalworking and plastic working machine operators (OR = 2.6, 95% CI 1.3-4.9) and handlers, and equipment cleaners and labourers (OR = 1.5, 95% CI 1.0-2.2). Allowing for a 10 year induction and latent period did not have a consistent effect on the associations. Potential exposures to asbestos, chromium, nickel, formaldehyde, diesel fumes, and cutting oils were assessed by using a job exposure matrix developed for this study. Three measures of exposure were examined--namely, peak, duration, and an intensity weighted exposure score. No significantly raised risks were seen, although increased risk was suggested among those exposed long term to formaldehyde in jobs with the highest exposures.

In plain English

This population-based case-control study in western Washington examined whether jobs and workplace exposures were linked to laryngeal (voice box) cancer. Interviews covered lifetime work, smoking and drinking for 235 people diagnosed from September 1983 to February 1987 (17 through surrogates) and 547 comparison people found by random digit dialling. After adjusting for smoking, alcohol, age and education, odds were significantly raised for painters, construction workers, supervisors and miscellaneous mechanics, metal and plastic working machine operators, and equipment cleaners and labourers. Industrial hygienists rated likely exposure to asbestos, chromium, nickel, formaldehyde, diesel fumes and cutting oils. None of these was significantly associated with laryngeal cancer, though the data suggested increased risk with medium or high formaldehyde exposure for 10 or more years. In the highest asbestos exposure-score group the odds ratio was 1.4 (95% CI 0.7 to 2.5). The authors concluded the data did not strongly support an asbestos association. They noted that the limitations make risk estimates conservative, and that the study had a 50% chance of detecting a doubled risk from 10 or more years of asbestos exposure.

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 using lifetime occupational histories from in-person interviews and a job exposure matrix
• Who was studied: There were 235 cases of laryngeal cancer with interviews, out of 291 found. Cases were aged 20 to 74, lived in the three largest counties of a 13 county area of western Washington and were diagnosed September 1983 to February 1987. For 17 of the 235 cases (7%), the interview was with a surrogate; the closest next of kin was interviewed if a case had died. There were 547 controls identified by random digit dialling.
• Exposure: Job titles were grouped into 62 categories. A panel of four industrial hygienists built a job exposure matrix rating exposure to six agents: asbestos, chromium, nickel, cutting oils, diesel fumes and formaldehyde. Each was coded none, low, medium or high and summarised as peak exposure, duration (less than 10 years or 10 years or more) and an intensity-weighted exposure score. The article does not specify asbestos fiber types.
• Main results:
  • Significantly raised odds ratios, adjusted for smoking, alcohol, age and education, were found for painters (OR 2.8, 95% CI 1.1-6.9) and construction workers (OR 3.4, 95% CI 1.4-8.1).
  • Supervisors and miscellaneous mechanics also had a significantly raised odds ratio (OR 2.3, 95% CI 1.1-4.8).
  • Plumbers and pipefitters had a raised odds ratio that was not statistically significant (OR 4.1, 95% CI 0.9-17.9).
  • Among people employed 10 years or more, construction workers had a significantly raised risk (OR 5.7, 95% CI 1.3-26.3). The trend test for increasing risk with duration was significant only for construction workers.
  • For all six job-exposure-matrix exposures, including asbestos, none of the summary measures (peak, duration, exposure score) was significantly associated with laryngeal cancer.
  • For asbestos, the group with an exposure score of 20 or more (37 cases, 42 controls) had an OR of 1.4 (95% CI 0.7-2.5). The authors said this possible association could easily be explained by chance.
  • The authors wrote that the data suggest formaldehyde is associated with laryngeal cancer among people with at least medium or high exposure for 10 or more years.
  • After excluding low-level exposures, the formaldehyde group with medium or high exposure for 10 years or more had an OR of 4.2 (95% CI 0.9-19.4) compared with the non-exposed. The high formaldehyde exposure score category had an OR of 4.3 (95% CI 1.0-18.7).
  • There were suggestions, not statistically significant, of increased risk with chromium and nickel in the high exposure score group. These two exposures largely overlapped.
• The authors' conclusion: The authors concluded that the data do not strongly support an association with asbestos, nickel or chromium. They added that the study's limitations work together to produce conservative estimates of relative risk, and that the suggestion of increased risk with formaldehyde needs replication.
• Limitations the authors state:
  • Statistical power was limited. For asbestos, the study had a 50% chance of detecting a twofold increase in risk among people exposed 10 years or more.
  • The job exposure matrix is a qualitative estimate, not actual measurement. Non-differential misclassification would bias results toward no effect.
  • Jobs involve multiple exposures, so a single agent cannot be singled out.
  • Many statistical comparisons were made, so some significant associations are expected by chance alone.

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: Case-Control Study, Laryngeal Cancer, Occupational Exposure, Odds Ratio, confidence interval.

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