Occupational asbestos exposure, smoking, and laryngeal carcinoma

Our plain-English summary of Occupational asbestos exposure, smoking, and laryngeal carcinoma, by R.W. Morgan, P.T. Shettigara (Annals of the New York Academy of Sciences, 1976).

The study

• Authors: R.W. Morgan, P.T. Shettigara
• Journal: Annals of the New York Academy of Sciences
• Published: 1976;271:308-10
• Cited by: 37 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001117).

Summary of the article

This study asked whether cancer of the larynx is related to occupational asbestos exposure. Smoking habits were also measured, mainly as a control variable. The cases were 54 men who had been treated for laryngeal cancer at the Toronto General Hospital and were alive on May 1, 1974. They represented all of the patients available. Each case was matched with one male control of similar age (within 5 years) who lived four or more doors to the right of the case. The same interviewer questioned all cases and controls using a mostly yes/no questionnaire, chosen to reduce interviewer bias. Telephone clerks later recontacted 51 cases and 52 controls to check the original answers. They took occupational histories, which were classified blind into three categories of probable asbestos exposure. Matched pairs were analysed with the McNemar test. In 13 pairs only the case reported asbestos exposure, and in 1 pair only the control did (relative risk 13; p<.001). Time from asbestos exposure to diagnosis ranged from 5 to 55 years, with a mean of 28.6 years. Risk rose with the number of cigarettes smoked, reaching a relative risk of 21.00 at 40 or more cigarettes. The asbestos risk appeared confined to smokers. The occupational histories appeared to confirm the interview data. No case-control differences were found for alcohol, uranium, chromium, cobalt, nickel, arsenic or medical irradiation. The authors concluded that laryngeal cancer must now be included among presumptive asbestos diseases unless evidence to the contrary is presented.

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 case-control study from the University of Toronto. It tested whether laryngeal cancer (cancer of the voice box) is related to occupational asbestos exposure. The cases were 54 men, alive on May 1, 1974, who had been treated at the Toronto General Hospital. Each was paired with a man of similar age living four or more doors away. Men answered mostly yes-or-no questions about asbestos exposure and smoking. Later, 51 cases and 52 controls were recontacted by telephone to check their answers against job histories. In 13 pairs only the case reported asbestos exposure, and in 1 pair only the control did. The authors gave this as a relative risk of 13. Risk rose with amount smoked, reaching a relative risk of 21.00 for the 40-or-more cigarette group compared with nonsmokers. The authors reported that the asbestos risk appeared confined to smokers. The article did not name asbestos fiber types. The authors concluded that laryngeal cancer must now be listed among presumptive asbestos diseases unless contrary evidence appears. They noted their numbers were small.

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: Matched case-control study (each case paired with one control), analyzed mainly with the McNemar test
• Who was studied: 54 male laryngeal cancer patients alive at May 1, 1974, treated at the Toronto General Hospital, Canada (100% of those available). Each was matched with a male control of similar age (within 5 years) living four or more doors to the right of the case.
• Exposure: Self-reported occupational asbestos exposure, asked with mostly yes/no questions. Exposure was checked by telephone job histories that were blindly classed as not probable, probable or almost certain asbestos exposure. Cigarette smoking was measured mainly as a control variable. No fiber types were named.
• Main results:
  • Among the 54 matched pairs, 13 pairs had only the case reporting asbestos exposure, 1 pair had only the control reporting it, and 40 pairs had neither. The authors reported a relative risk of 13, described as highly significant.
  • About 24% of laryngeal cancer cases and almost no controls reported asbestos exposure.
  • Among exposed men, time from asbestos exposure to diagnosis ranged from 5 to 55 years, with a mean of 28.6 years.
  • Mean age at diagnosis was 59.8 years for exposed cases and 60.6 years for nonexposed cases.
  • Risk rose with amount smoked, using nonsmokers as the reference (3 cases, 14 controls, relative risk 1.00). The relative risks were 1.17 for 1-9 cigarettes, 2.33 for 10-19, 8.00 for 20-29 and 10.50 for 30-39. The 40-or-more group had 9 cases, 2 controls and a relative risk of 21.00.
  • When pairs were grouped by both smoking and asbestos exposure, there was a 21 to 2 split in 23 discordant pairs (binomial p less than 0.001). The authors stated that the asbestos risk appeared confined to men who smoke.
  • In the job-history check, 14 men had answered yes to asbestos exposure. Of these, 1 was classed not probable, 6 probable, 6 almost certain and 1 not available. Of 94 who answered no, 71 were classed not probable, 18 probable, 1 almost certain and 4 not available. The authors said this appeared to confirm the interview data.
  • No case-control differences were found in exposure to alcohol, uranium, chromium, cobalt, nickel, arsenic or medical irradiation.
  • There was no appreciable difference between current and former smokers.
• The authors' conclusion: The authors said they were confident the case-control differences were real. They stated that, in this study, the risk from asbestos was confined to smokers. They concluded that laryngeal cancer must now be included among presumptive asbestos diseases unless evidence is presented to the contrary.
• Limitations the authors state:
  • The authors noted their numbers were small.
  • The interviewer could not be kept unaware of whether a respondent was a case or a control. The authors used closed yes/no questions to reduce interviewer bias.

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, Laryngeal Cancer, Habit, Relative Risk.

Related studies

• Occupational risk factors for laryngeal carcinoma: Connecticut, 1975-1980 — R.T. Zagraniski, J.L. Kelsey, et al. (1986)
• Asbestos, dental X-rays, tobacco, and alcohol in the epidemiology of laryngeal cancer — M.W. Hinds, D.B. Thomas, et al. (1979)
• The joint effect of asbestos exposure, tobacco smoking and alcohol drinking on laryngeal cancer risk: evidence from the French population-based case-control study, ICARE — G. Menvielle, A. Fayossé, et al. (2016)
• The history, aetiology and epidemiology of laryngeal carcinoma — M.A. Rafferty, J.E. Fenton, et al. (2001)
• Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study — J.L. Marchand, D. Luce, et al. (2000)
• Occupational asbestos exposure as a risk factor for laryngeal carcinoma in a population-based case-control study from Germany — H. Ramroth, W. Ahrens, et al. (2011)

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