Asbestos, dental X-rays, tobacco, and alcohol in the epidemiology of laryngeal cancer

Our plain-English summary of Asbestos, dental X-rays, tobacco, and alcohol in the epidemiology of laryngeal cancer, by M.W. Hinds, D.B. Thomas, H.P. O'Reilly (Cancer, 1979).

The study

• Authors: M.W. Hinds, D.B. Thomas, H.P. O'Reilly
• Journal: Cancer
• Published: 1979;44(3):1114-20
• Cited by: 70 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. 001030).

Abstract

A case-control study of 47 laryngeal cancers in males of three counties of Washington State was conducted. Personal interview was used to obtain information on smoking, alcohol use, exposure to asbestos, and other substances, and x-rays of the head and neck area. Smoking and alcohol consumption were found to increase risk of laryngeal cancer independently, with a clear dose-response relationship. Neither asbestos exposure nor exposure to other substances was found to significantly increase the risk of laryngeal cancer, although the relative risk with asbestos exposure was 1.75. Lifetime history of exposure to dental x-rays on five or more occasions was associated with significantly increased risk of laryngeal cancer among heavy smokers but not among light smokers. The importance of tobacco and alcohol in the epidemiology of laryngeal cancer was re-affirmed, the importance of asbestos exposure was brought into question, and a possible relationship of laryngeal cancer with exposure to dental x-rays among heavy smokers was demonstrated.

In plain English

This case-control study compared 47 men diagnosed with cancer of the larynx (voice box) while living in Pierce, King or Kitsap counties, Washington State, from January 1976 to June 1977, with 47 neighbors matched for sex, race and 10-year age group. Interviews covered jobs, smoking, alcohol, asbestos and other exposures, and head and neck x-rays. Exposure to asbestos, counted for anyone reporting work with or near asbestos dust, was reported by 25 cases (53.2%) and 19 controls (40.4%). The matched-pair relative risk was 1.75, which was not statistically significant, and no dose-response effect was found. Smoking and alcohol were each linked to higher risk, rising with the amount. Among heavy smokers (21 or more cigarettes a day), 10 or more dental x-ray visits, compared with 0 to 4, carried a significant relative risk of 7.5. Light smokers showed no increase. The authors concluded their findings did not support asbestos as an important risk factor, although 1.75 was consistent with a small risk. They cautioned that the dental x-ray finding rested on few cases and may not be real.

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 personal interviews, with one neighborhood control per case matched for sex, race and 10-year age group
• Who was studied: Males diagnosed with laryngeal cancer while residents of Pierce, King or Kitsap counties, Washington State, between January 1, 1976 and June 30, 1977, identified through the Cancer Surveillance System of the Fred Hutchinson Cancer Research Center. Of 69 cases identified, 47 were included. The other 22 were excluded because the physician was unwilling (10), the patient had died with no close relatives (8), could not be located (2) or refused (2). Each case had one matched neighborhood control, for 94 subjects in all. All 47 cases were Caucasian.
• Exposure: Self-reported asbestos exposure, with no fiber type specified. Anyone who reported working directly with or near asbestos dust was counted as exposed. Reported sources were shipyards, brake repair and construction. The study also examined cigarette smoking, alcohol, dental and other head and neck x-rays, and self-reported exposure to arsenic, nickel, uranium, chromium and cobalt.
• Main results:
  • A history of asbestos exposure was reported by 25 of 47 cases (53.2%) and 19 of 47 controls (40.4%).
  • In the matched-pair analysis, only the case was exposed to asbestos in 14 pairs and only the control in 8 pairs. This gave a relative risk of 1.75 (p = .21), which was not statistically significant.
  • Duration of asbestos exposure was similar for exposed cases (mean 8.4 years) and exposed controls (mean 8.3 years), and no dose-response effect was shown. The association was not significant in any subgroup of pairs: glottic cancer (RR 1.29, p .63), supraglottic cancer (RR 4.00, p .22), pairs matched on smoking (RR 3.00, p .37) and pairs matched on alcohol (RR 1.33, p .73). The relative risk was above 1.00 in every subgroup.
  • Smoking showed a dose-response relationship with laryngeal cancer. Relative to fewer than 10 cigarettes per day, the relative risk was 7.43 for 10-20 per day, 13.54 for 21-40 per day and 20.00 for more than 40 per day (test for trend p less than .001). Only 1 case but 8 controls were nonsmokers.
  • Alcohol was associated with laryngeal cancer and strongly suggested a dose-response relationship. Relative to less than 1 unit per day, the relative risk was 2.05 (not significant) for 1-2 units, 3.79 for 3-6 units and 9.01 for more than 6 units per day.
  • Among heavy smokers (21 or more cigarettes per day), 10 or more dental x-ray visits carried a relative risk of 7.5 (p less than .02) compared with 0-4 visits. Among light smokers (20 or fewer per day), no increased risk was found.
  • Across all matched pairs, only the case had five or more dental x-ray visits in 12 pairs and only the control in 5 pairs, which was not significant. Stratified by smoking, a significant association was found among heavy smokers.
  • Very few subjects reported exposure to arsenic, nickel, uranium, chromium or cobalt, and none of these was significantly associated with laryngeal cancer.
• The authors' conclusion: The authors concluded that their findings did not support the hypothesis that asbestos exposure is an important risk factor for laryngeal cancer, though the relative risk of 1.75 was consistent with a small risk. They considered the relationship open to question. They also said the possible link between dental x-rays and laryngeal cancer in heavy smokers called for further investigation.
• Limitations the authors state:
  • The dental x-ray finding was based on a small number of cases and may not be real.
  • Dental visits and x-rays are likely linked to other factors, such as diet, that were not controlled for.
  • The broad, open-ended smoking and alcohol categories did not allow analysis of whether the two act together (synergism).
  • Too few people reported other head and neck x-rays for a meaningful analysis.

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: Epidemiology, Laryngeal Cancer, Case-Control Study, Dose-response relationship, Asbestos Exposure, Relative Risk.

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