A case-control study on occupational lung cancer risks in an industrialized city of Japan

Our plain-English summary of A case-control study on occupational lung cancer risks in an industrialized city of Japan, by N. Yamaguchi, M. Kido, T. Hoshuyama, et al (Japanese Journal of Cancer Research, 1992).

The study

• Authors: N. Yamaguchi, M. Kido, T. Hoshuyama, H. Manabe, Y. Kikuchi, T. Nishio, L.H. Ohshima, S. Watanabe
• Journal: Japanese Journal of Cancer Research
• Published: 1992;83(2):134-40
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A hospital-based case-control study was conducted to evaluate occupational risks of lung cancer in an industrialized city of Japan. The lung cancer cases were obtained from 3 major hospitals in the city. The control group consisted of patients with a variety of diseases hospitalized in the same wards of the same hospitals as the cases. After matching on sex, 5-year age category and hospital, 144 cases and 676 controls comprised the study group. A self-administered questionnaire was used to obtain lifetime job histories and smoking status. The conditional logistic regression model was used to estimate relative risks after controlling for smoking and employment in other jobs. The workers in shipbuilding, ironworks and other plants (mostly chemical plants) showed statistically significant increases in lung cancer risk with relative risks of 6.18, 2.02, and 2.66, respectively. An increase in risk with the duration of employment was also observed in the "other plants" category. Building and road construction workers also showed increased relative risks, 1.95 and 1.79, but they were not significant. When the risk was evaluated on the exposure chemicals, the workers exposed to inorganic acids and bases had significantly increased risk. The workers exposed to asbestos, dust or organic chemicals also showed increased risk but the effects were not significant. The combined effect of smoking and employment in ironworks showed a good fit to an additive model, while that in the "other plants" category was closer to a multiplicative model.

In plain English

Researchers studied lung cancer and work history in Kitakyushu City, an industrialized city of Japan. They compared 144 lung cancer patients with 676 patients with other diseases from the same wards of three major hospitals (July 1989 to September 1990), matched by hospital, sex and 5-year age group. Patients filled in a questionnaire on jobs, workplace exposures and smoking. Asbestos was one listed exposure, and no fiber type was specified. After accounting for smoking and other jobs, lung cancer risk was significantly higher among shipbuilding workers (relative risk 6.18), workers in "other plants", mostly chemical plants (2.66), and ironworks workers (2.02). Building and road construction workers had higher risks that were not statistically significant. Workers reporting exposure to inorganic acids or bases had a significantly raised risk (4.03). Workers reporting asbestos exposure had a relative risk of 1.94 (95% confidence interval 0.49 to 7.78), which was not statistically significant. The authors noted that shipbuilding cases were few and called for further investigations to confirm the findings.

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: Hospital-based case-control study, analysed with conditional logistic regression
• Who was studied: 144 histologically confirmed lung cancer cases (117 males, 27 females) and 676 controls (479 males, 197 females) hospitalized with other diseases in the same wards of three major hospitals in Kitakyushu City, Japan, July 1, 1989 to September 1, 1990. Matched on hospital, sex and 5-year age category.
• Exposure: Self-reported lifetime work in seven job categories: mining, steel manufacturing, ironworks, building construction, road construction, shipbuilding, and other plants. Also yes/no questions on workplace chemicals, including asbestos (no fiber type specified), plus smoking status.
• Main results:
  • Relative risk of lung cancer was significantly increased among shipbuilding workers (RR 6.18, 95% CI 1.54 to 24.88), workers in "other plants" (RR 2.66, 95% CI 1.43 to 4.94) and ironworks workers (RR 2.02, 95% CI 1.06 to 3.88)
  • Building construction workers (RR 1.95) and road construction workers (RR 1.79) had increased relative risks that were not statistically significant
  • Workers reporting exposure to asbestos had a relative risk of 1.94 (95% CI 0.49 to 7.78), which was not statistically significant
  • Workers exposed to inorganic acids or bases had a significantly increased risk (RR 4.03, 95% CI 1.05 to 15.51)
  • Current smokers of more than 20 cigarettes a day had the highest risk (RR 12.14, 95% CI 5.10 to 28.90)
  • In the "other plants" category, risk tended to increase with duration of employment (RR 2.25 for 15 years or less, 3.37 for more than 15 years). Taking duration into account did not significantly improve model fit.
  • The combined effect of smoking and ironworks employment was closer to an additive model. For "other plants" it was closer to a multiplicative model.
• The authors' conclusion: The authors concluded that further investigations are needed to confirm these findings and to identify the specific chemicals or other risk factors causing the increased risks observed
• Limitations the authors state:
  • The authors said the selection of hospital controls and questionnaire data collection were potential sources of bias
  • The authors said misclassification from the self-administered questionnaire could have led to underestimated relative risks
  • The number of lung cancer cases among shipbuilding workers was small, so the size of that risk is imprecise
  • Analysis by histologic type of lung cancer was not possible because of inadequate numbers of cases

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: Case-Control Study, Lung Cancer, Relative Risk.

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