Occupational exposures contribute to educational inequalities in lung cancer incidence among men: Evidence from the EPIC prospective cohort study

Our plain-English summary of Occupational exposures contribute to educational inequalities in lung cancer incidence among men: Evidence from the EPIC prospective cohort study, by G. Menvielle, H. Boshuizen, A.E. Kunst, et al (International Journal of Cancer, 2010).

The study

• Authors: G. Menvielle, H. Boshuizen, A.E. Kunst, P. Vineis, S.O. Dalton, M.M. Bergmann, S. Hermann, F. Veglia, P. Ferrari, K. Overvad, O. Raaschou-Nielsen, A. Tjønneland, R. Kaaks, J. Linseisen, D. Palli, V. Krogh, R. Tumino, L. Rodriguez, A. Agudo, M.J. Sánchez, J.M.A. Arozena, L. Cirera, E. Ardanaz, S. Bingham, K.T. Khaw, P. Boffetta, E. Duell, N. Slimani, V. Gallo, E. Riboli, H.B. Bueno-de-Mesquita
• Journal: International Journal of Cancer
• Published: 2010;126(8):1928-1935
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The aim of this study is to investigate to what extent occupational exposures may explain socioeconomic inequalities in lung cancer incidence after adjusting for smoking and dietary factors. Analyses were based on a subsample of the European Prospective Investigation into Cancer and Nutrition (EPIC study), a prospective cohort. The analyses included 703 incident lung cancer cases among men in Denmark, the United Kingdom, Germany, Italy, Spain and Greece. The socioeconomic position was measured using the highest level of education. The estimates of relative indices of inequality (RII) were computed with Cox regression models. We first adjusted for smoking (with detailed information on duration and quantity) and dietary factors (fruits and vegetables consumption) and then for occupational exposures. The exposure to three carcinogens [asbestos, heavy metals and polycyclic aromatic hydrocarbons (PAH)] was analyzed. The occupational exposures explained 14% of the socioeconomic inequalities remaining after adjustment for smoking and fruits and vegetables consumption. The inequalities remained nevertheless statistically significant. The RII decreased from 1.87 (95% CI: 1.36-2.56) to 1.75 (1.27-2.41). The decrease was more pronounced when adjusting for asbestos than for heavy metals or PAH. Analyses by birth cohort suggested an effect of occupational exposures among older men, while due to small number of endpoints, no conclusion could be drawn about the role of occupational exposures in educational inequalities among younger men. Our study revealed that the impact of occupational exposures on socioeconomic inequalities in cancer incidence, rarely studied until now, exists while of modest magnitude.

In plain English

This prospective cohort study, using part of the European EPIC cohort, examined how far jobs involving carcinogens explain higher lung cancer rates among less-educated men. It included 88,265 men from 15 centers in six countries, among whom 703 lung cancers occurred. Exposure to asbestos, heavy metals and polycyclic aromatic hydrocarbons (PAH) was scored as the number of jobs held from a list of hazardous occupations; duration and level were not known. Men with three or more asbestos-exposed jobs had a hazard ratio of 1.65 (95% CI 1.11–2.46) compared with never-exposed men. After adjusting for smoking and fruit and vegetable intake, the inequality index comparing least and most educated men fell from 1.87 (1.36–2.56) to 1.75 (1.27–2.41) when all three exposures were added. This reduced the excess risk by 14%, and asbestos produced the largest drop. The inequality remained statistically significant. The reduction appeared in men born before or in 1941. Among younger men, numbers were too small for conclusions. The authors concluded that the contribution of occupational exposures exists but is of modest magnitude.

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: Prospective cohort study (analysis of a subsample of the European Prospective Investigation into Cancer and Nutrition, EPIC)
• Who was studied: 88,265 men from 15 EPIC centers in Spain, Greece, Denmark, Germany, Italy and the United Kingdom. They were recruited in the 1990s and followed until between December 2002 and December 2006, with a mean follow-up of 8.4 years. There were 703 incident lung cancer cases. Women were excluded because few exposed women developed lung cancer.
• Exposure: Occupational exposure to asbestos (fiber type not specified), heavy metals and PAH. Each was scored as the number of jobs a man reported holding from a list of 52 occupations linked to cancer, grouped as never exposed, 1, 2, or 3 or more jobs. There was no information on duration or level of exposure. Education level was the measure of socioeconomic position.
• Main results:
  • Among all men, after adjustment for smoking, diet and education, the hazard ratios for lung cancer compared with never-exposed men were: 1.65 (95% CI 1.11–2.46) for 3 or more asbestos-exposed jobs, 1.34 (0.95–1.89) for 2 jobs and 1.16 (0.95–1.42) for 1 job.
  • The association with lung cancer was weaker and not statistically significant for heavy metals, and absent for PAH.
  • Among all men, the relative index of inequality (RII, comparing the least and most educated) was 3.01 (2.21–4.09) unadjusted and 1.87 (1.36–2.56) after adjustment for smoking and fruit and vegetable consumption. Adding asbestos alone gave 1.76 (1.28–2.41), a statistically significant decrease (p = 0.01). Adding heavy metals gave 1.83 (p = 0.13) and adding PAH gave 1.84 (p = 0.55).
  • Among all men, adding all three exposures together lowered the RII from 1.87 to 1.75 (1.27–2.41). This reduced the excess risk by 14%, from 87% to 75% (p = 0.05). The remaining inequality stayed statistically significant.
  • Among men born before or in 1941 (551 cases), the RII fell from 2.33 (1.61–3.36) to 2.14 (1.47–3.12) after adding all three exposures (p = 0.03). The remaining inequality stayed statistically significant.
  • Among men born after 1941 (152 cases), the RII estimates were close to 1, with wide confidence intervals, and were not statistically significant once smoking and diet were adjusted for. The RII was 0.94 (0.50–1.77) in the reference model and 0.88 (0.46–1.69) with all three exposures added.
  • A higher proportion of less-educated men had held jobs involving these exposures. For asbestos, 26.1% of men with primary education or less had held such a job, compared with 12.0% of men with university or vocational postsecondary education.
• The authors' conclusion: The authors concluded that occupational exposures do contribute to educational inequalities in lung cancer incidence among men, but only to a modest degree. They added that tobacco control remains the key element in reducing these inequalities.
• Limitations the authors state:
  • Exposure was assigned from job titles using a predefined, non-exhaustive list of occupations. There was no information on duration, level or intensity of exposure.
  • Exposure misclassification may differ by education. Exposure may have been missed more often among highly educated men, and the size of the resulting bias cannot be estimated.
  • Some carcinogens, such as welding fumes, were not measured, so the estimates may be conservative.
  • Analyses of younger men were based on small numbers, so chance cannot be ruled out. Because of long lag times between exposure and cancer, this generation may also be too young to show an effect.
  • The results concern relative inequalities. Conclusions about absolute inequalities may be partly different.

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: Occupational Exposure, Lung Cancer, Cohort Study.

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