Asbestos exposure as a risk factor for retroperitoneal fibrosis

Our plain-English summary of Asbestos exposure as a risk factor for retroperitoneal fibrosis, by T. Uibu, P. Oksa, A. Auvinen, et al (Lancet, 2004).

The study

• Authors: T. Uibu, P. Oksa, A. Auvinen, E. Honkanen, K. Metsärinne, H. Saha, J. Uitti, P. Roto
• Journal: Lancet
• Published: 2004;363(9419):1422-6
• Cited by: 129 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Retroperitoneal fibrosis (RPF) is an uncommon disease with unknown causation in most cases. The pathognomonic finding is a fibrous mass covering the abdominal aorta and the ureters. Our aim was to clarify the possible role of asbestos exposure in the development of RPF. The hypothesis was based on the ability of asbestos to cause fibrosis in pulmonary and pleural tissue.

Methods: We undertook a case-control study of 43 patients with the disease (86% of eligible cases) treated in three university hospital districts of Finland in 1990-2001. For every patient, five population-based controls were selected, matched by age, sex, and central hospital district. We assessed asbestos exposure and medical history using a postal questionnaire and a personal interview. Of the 215 eligible controls, 179 (83%) participated in the study.

Findings: The age-standardised incidence of RPF was 0.10 (95% CI 0.07-0.14) per 100?000 person-years. The disease was strongly associated with asbestos exposure. The odds ratio (OR) was 5.54 (1.64-18.65) for less than 10 fibre-years of asbestos exposure and 8.84 (2.03-38.50) for 10 or more fibre-years, the attributable fraction being 82% and 89%, respectively. Other risk factors were previous use of ergot derivates (OR 9.92 [1.63-60.26]), abdominal aortic aneurysm (OR 6.73 [0.81-56.08]), and smoking for more than 20 pack-years (OR 4.73 [1.28-17.41]).

Interpretation: Our results show that occupational asbestos exposure is an important causal factor for RPF. For patients with work-related asbestos exposure, RPF should be considered an occupational disease.

In plain English

This case-control study from Finland examined whether asbestos exposure was linked to retroperitoneal fibrosis (RPF), a rare disease in which a fibrous mass covers the abdominal aorta and ureters. The authors studied 43 living patients treated in three university hospital districts in 1990–2001 and 179 population controls matched by birth year, sex and district. Exposure information came from questionnaires and interviews, and an expert who did not know who was a patient graded it in fibre-years. Asbestos exposure was found in 22 patients (51%) and 48 controls (27%). After adjustment for other factors, the odds ratio for RPF was 5.54 (95% CI 1.64 to 18.65) for under 10 fibre-years and 8.84 (2.03 to 38.50) for 10 or more. Ergot medication and smoking over 20 pack-years were also associated with RPF. The authors concluded that occupational asbestos exposure was "an important causal factor" for RPF. They also wrote that classing RPF as an occupational disease should be considered if other studies support the results. They noted that interviewers could not be masked and that only living people were studied.

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 (cases and controls had to be alive at the time of the study, which the authors call prevalence sampling)
• Who was studied: 43 adult patients with RPF (86% of 50 eligible) diagnosed and treated in 12 hospitals within three university hospital districts of Finland in 1990–2001. Controls were 5 per case, matched for year of birth, sex and central hospital district and drawn from the Finnish population register; 179 of 215 controls (83%) took part.
• Exposure: Cumulative asbestos exposure, fiber type not specified. It was estimated in fibre-years by an expert from questionnaire and interview data and graded as none, slight (more than 1 week of low-level exposure and less than 10 fibre-years), or moderate to high (10 fibre-years or more). The grading physician was masked to case-control status. Occupations with 10 or more fibre-years included construction worker, insulator, construction cleaner, electrician and shipyard worker.
• Main results:
  • The age-standardised incidence of RPF in the study area was 0.10 (95% CI 0.07–0.14) per 100 000 person-years overall in 1990–2001.
  • 22 of 43 cases (51%) and 48 of 179 controls (27%) had a positive asbestos exposure history.
  • Exposures above 10 fibre-years were all occupational.
  • Crude (unadjusted) odds ratios for RPF were 4.2 (95% CI 1.6–11.0) for less than 10 fibre-years and 4.1 (1.4–12.4) for 10 or more fibre-years.
  • After adjustment for other risk factors, the odds ratio for RPF was 5.54 (1.64–18.65) for less than 10 fibre-years and 8.84 (2.03–38.50) for 10 or more fibre-years.
  • Among exposed cases, the fraction attributable to asbestos was 82% (95% CI 39–95) for slight exposure and 89% (51–97) for moderate to high exposure.
  • The population attributable fraction was 25% (12–29) for less than 10 fibre-years and 19% (11–20) for 10 or more fibre-years. The authors say these figures are likely overestimates.
  • Adjusted odds ratio for previous use of ergot derivates: 9.92 (1.63–60.26).
  • Adjusted odds ratio for a smoking history of more than 20 pack-years: 4.73 (1.28–17.41). There was no significant interaction between smoking and asbestos exposure.
  • Adjusted odds ratio for abdominal aortic aneurysm: 6.73 (0.81–56.08). The confidence interval includes 1.
  • Mean time from first exposure to RPF was 30.8 (SD 12.3) years for slight exposure and 33.3 (7.3) years for moderate to high exposure.
• The authors' conclusion: The authors concluded that occupational asbestos exposure is an important causal factor for RPF and that, for patients with work-related asbestos exposure, RPF should be considered an occupational disease. In the discussion they put this more conditionally: if other investigations support the results, classification of RPF as an occupational disease should be considered.
• Limitations the authors state:
  • Only living cases and controls were studied, so factors linked to disease risk could not be separated from factors linked to a favourable outlook. The authors judged this distortion likely to be small.
  • Interviews could not be conducted masked to disease status.
  • The population attributable fraction for asbestos was likely overestimated because men and older people were over-represented.
  • Equivalent detailed information on abdominal surgery could not be obtained for controls, so the negative surgery result does not rule out surgery as a cause.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Fibrosis, Causation, Case-Control Study, Odds Ratio, Occupational Disease.

Related studies

• Asbestos-related pleural and lung fibrosis in patients with retroperitoneal fibrosis — T. Uibu, R. Järvenpää, et al. (2008)
• Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study — M. Goldoni, S. Bonini, et al. (2014)
• Asbestos exposure: a potential cause of retroperitoneal fibrosis — R. Sauni, P. Oksa, et al. (1998)
• Idiopathic retroperitoneal fibrosis: prospective evaluation of incidence and clinicoradiologic presentation — E.F.H. van Bommel, I. Jansen, et al. (2009)
• Syndrome of pleural and retrosternal "bridging" fibrosis and retroperitoneal fibrosis in patients with asbestos exposure — V. Cottin, P.Y. Brillet, et al. (2008)
• Idiopathic retroperitoneal fibrosis: an update for nephrologists — V. Raglianti, G.M. Rossi, et al. (2021)

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