Colon cancer, physical activity, and occupational exposures. A case-control study

Our plain-English summary of Colon cancer, physical activity, and occupational exposures. A case-control study, by M. Fredriksson, N.O. Bengtsson, L. Hardell, et al (Cancer, 1989).

The study

• Authors: M. Fredriksson, N.O. Bengtsson, L. Hardell, O. Axelson
• Journal: Cancer
• Published: 1989;63(9):1838-42
• Cited by: 104 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. 000080).

Abstract

A case-control study on colon cancer was conducted encompassing 329 cases and 658 controls. Occupations and various exposures were assessed by questionnaires. A decreased risk was found in persons with physically active occupations. This effect was most pronounced in colon descendens and sigmoideum with an odds ratio (OR) of 0.49 whereas no reduced risk was found for right-sided colon cancer. Regarding specific jobs, reduced ORs were found for agricultural, forestry, and saw mill workers and increased OR for railway employees. High-grade exposure to asbestos or to organic solvents gave a two-fold increased risk. Regarding exposure to trichloroethylene in general, a slightly increased risk was found whereas such exposure among dry cleaners gave a seven-fold increase of the risk.

In plain English

This Swedish case-control study included 329 people aged 30 to 75 diagnosed with colon cancer in 1980 to 1983 in northern Sweden and 658 controls of the same sex and county, closest in age. After 17 cases refused and 35 controls were lost, 156 male and 156 female cases and the remaining controls answered a mailed job and exposure questionnaire. Experts rated exposure to asbestos (fiber type not named), impregnating agents and organic solvents as high grade or low grade. People with physically active jobs had lower odds of cancer in the descending and sigmoid colon (odds ratio 0.49, 95% confidence interval 0.25 to 0.93) but not of right-sided colon cancer. Male railway workers had an odds ratio of 2.4 (1.1 to 5.1). For high-grade asbestos exposure the odds ratio was 2.1 (0.8 to 5.8). The authors called this a somewhat increased risk but noted the confidence interval included 1. High-grade organic solvent exposure gave 2.1 (0.8 to 5.8), and trichloroethylene exposure among dry cleaners gave 7.4 (1.1 to 47.0). The authors concluded that physically active jobs showed a decreased colon cancer risk.

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: Case-control study using mailed questionnaires on occupational history and exposures; Mantel-Haenszel analysis
• Who was studied: 329 cases (165 men, 164 women) aged 30 to 75 were included. They had large bowel adenocarcinoma diagnosed 1980 to 1983, were reported to the Swedish Cancer Registry, lived in the region served by the Department of Oncology in Umeå, and were alive at data collection (1984 to 1986). 658 controls were drawn from the National Population Register, two per case, of the same county and sex and closest in age. 17 cases refused, leaving 156 male and 156 female cases. 35 controls were lost for the same reason, and 306 male controls and the remaining female controls answered the questionnaire.
• Exposure: Job-related physical activity was scored as sedentary, intermediate or high. Occupations were examined. Occupational exposure to asbestos (fiber type not specified), impregnating agents and organic solvents was classified as high grade or low grade by two physicians and one hygienist. Other agents included trichloroethylene, pesticides, glasswool and rockwool.
• Main results:
  • High-grade asbestos exposure: odds ratio 2.1 (95% confidence interval 0.8 to 5.8)
  • The authors noted that the confidence interval for the increased risk with high-grade asbestos exposure included unity
  • Physically active jobs compared with sedentary jobs, cancer of the descending colon and sigmoid colon: odds ratio 0.49 (95% confidence interval 0.25 to 0.93)
  • No reduced risk was found for right-sided colon cancer among people with physically active jobs
  • Employment years in physically active jobs, compared in terms of a formal odds ratio: 0.82 for males and 0.68 for females
  • Railway employees: odds ratio 2.4 (95% confidence interval 1.1 to 5.1) in men and 2.3 (0.4 to 11.6) in women
  • Men in agricultural, forestry and saw mill work had reduced odds ratios of 0.7 (0.4 to 1.0), 0.7 (0.4 to 1.0) and 0.5 (0.3 to 0.9), respectively
  • High-grade exposure to organic solvents: odds ratio 2.1 (95% confidence interval 0.8 to 5.8)
  • Trichloroethylene exposure among dry cleaners: odds ratio 7.4 (95% confidence interval 1.1 to 47.0)
  • Odds ratios for exposure to man-made fibers (glasswool and rockwool) were below 1
• The authors' conclusion: The authors concluded that jobs classified as physically active showed a decreased risk for colon cancer, most marked for the descending and sigmoid colon.
• Limitations the authors state:
  • Diet, drugs and similar factors were analyzed in a separate report and were considered only to some extent as possible confounders here
  • For the trichloroethylene finding, the authors stated that further studies are needed before definitive conclusions

Topics

The National Library of Medicine indexes this study under subjects our site covers: Colon cancer.

Medical terms in this study, explained in our Lexicon: Colorectal Cancer, Occupational Exposure, Case-Control Study, Odds Ratio.

Related studies

• Asbestos exposure, physical activity and colon cancer: a case-control study — P. Vineis, G. Ciccone, et al. (1993)
• A case-control study of the relationship between the risk of colon cancer in men and exposures to occupational agents — M.S. Goldberg, M.E. Parent, et al. (2001)
• Identification of occupational cancer risks in British Columbia, Canada: a population-based case-control study of 1,155 cases of colon cancer — R. Fang, N. Le, et al. (2011)
• Asbestos and colon cancer: lack of association in a large case-control study — D.H. Garabrant, R.K. Peters, et al. (1992)
• Sinonasal cancer and occupational exposures: a pooled analysis of 12 case-control studies — D. Luce, A. Leclerc, et al. (2002)
• Occupational Asbestos Exposure and Incidence of Colon and Rectal Cancers in French Men: The Asbestos-Related Diseases Cohort (ARDCo-Nut) — C. Paris, I. Thaon, et al. (2017)

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