Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study

Our plain-English summary of Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study, by M. Goldoni, S. Bonini, M.L. Urban, et al (Annals of Internal Medicine, 2014).

The study

• Authors: M. Goldoni, S. Bonini, M.L. Urban, A. Palmisano, G. De Palma, E. Galletti, M. Coggiola, C. Buzio, A. Mutti, A. Vaglio
• Journal: Annals of Internal Medicine
• Published: 2014;161(3):181-8
• Cited by: 62 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Idiopathic retroperitoneal fibrosis (RPF) is a rare disease. Asbestos exposure has been proposed as a risk factor for idiopathic RPF.

Objective: To investigate the role of asbestos and other occupational agents (such as silica, metals, and organic solvents), as well as environmental agents (such as smoking), and their interactions as potential risk factors for idiopathic RPF.

Design: Case-control study.

Setting: National referral hospital for idiopathic RPF.

Patients: 90 patients with idiopathic RPF and 270 control participants matched for age, sex, and region of residency.

Measurements: Occupational history was obtained using structured questionnaires administered by blinded specialists in occupational medicine. Exposure to nonoccupational agents and presence of diseases that were potentially predisposing to idiopathic RPF were assessed through patient interviews and examination of medical records.

Results: A history of asbestos exposure was associated with idiopathic RPF (odds ratio [OR], 4.22 [95% CI, 2.14 to 8.33]). Both current smoking (OR, 3.21 [CI, 1.46 to 7.07]) and former smoking (OR, 2.93 [CI, 1.39 to 6.14]) were more prevalent among patients than among those who never smoked. A multiplicative effect was found between tobacco smoke and both occupational asbestos exposure (OR, 12.04 [CI, 4.32 to 38.28]) and extraoccupational asbestos exposure (OR, 8.42 [CI, 2.77 to 30.58]).

Limitation: Retrospective, questionnaire-based assessment of occupational exposure.

Conclusion: Exposure to asbestos and tobacco smoke resulted in strong risk factors for idiopathic RPF. Coexposure to asbestos and smoke had a multiplicative effect on risk compared with single exposure.

Primary Funding Source: None.

In plain English

This Italian case-control study compared 90 patients with idiopathic retroperitoneal fibrosis (RPF) with 270 control participants matched for age, sex and region. Patients were seen at the nephrology unit of University Hospital of Parma from January 2005 to October 2012. Controls were relatives or friends of patients coming there for kidney transplantation. Blinded occupational medicine specialists interviewed everyone with structured questionnaires. Possible, probable or documented occupational asbestos exposure was reported by 31 of 90 patients and 31 of 270 controls. After adjustment, occupational exposure had an odds ratio of 4.22 (95% CI 2.14 to 8.33) compared with people who had no asbestos exposure or only extraoccupational (non-work) exposure. Compared with nonsmokers, current smokers had 3.21 (1.46 to 7.07) and former smokers 2.93 (1.39 to 6.14). Current or former smokers with occupational exposure had 12.04 (4.32 to 38.28) compared with nonsmokers without occupational exposure. Silica, metals, organic solvents and other workplace agents showed no significant association. The authors concluded that reported asbestos exposure and smoking were strong risk factors, with a multiplicative effect when combined. They noted that few participants were exposed to asbestos without smoking.

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: Matched case-control study (3 control participants per patient), with exposure assessed by interviewer-administered structured questionnaire
• Who was studied: 90 patients with idiopathic RPF (62 men, 28 women), out of 102 considered. They were diagnosed at or referred to the nephrology unit of University Hospital of Parma, Italy, January 2005 to October 2012. The 270 control participants were matched for age (5 years), sex and region of origin. They were recruited among relatives or friends of patients coming to the unit for kidney transplantation.
• Exposure: Asbestos exposure was classified by Italian National Mesothelioma Register criteria as documented, probable or possible occupational, extraoccupational (including familiar and environmental), or none. Fiber types were not specified. The study also looked at tobacco smoking (current, former, pack-years) and other occupational agents (chemicals, metallic elements, pesticides, silica, organic solvents).
• Main results:
  • Occupational asbestos exposure (possible, probable or documented) was reported by 31 of 90 patients (34%) and 31 of 270 controls (11%). Compared with no or only extraoccupational exposure, the crude odds ratio was 4.81 (95% CI 2.51 to 9.17).
  • One adjusted model treated asbestos as a yes/no variable: occupational exposure versus no exposure or extraoccupational exposure. In it, occupational asbestos exposure had an odds ratio of 4.22 (95% CI 2.14 to 8.33). Current smokers versus nonsmokers had 3.21 (1.46 to 7.07), and former smokers versus nonsmokers had 2.93 (1.39 to 6.14).
  • Another adjusted model kept the asbestos categories separate, each compared with no asbestos exposure. Extraoccupational exposure had an odds ratio of 2.86 (1.48 to 5.48). Possible or probable occupational exposure had 6.17 (2.81 to 13.56), and documented occupational exposure had 4.63 (1.49 to 14.41).
  • In a combined analysis, the comparison group was nonsmokers without occupational asbestos exposure, a group that included extraoccupational exposure. Against this group, current or former smokers with occupational exposure had an odds ratio of 12.04 (95% CI 4.32 to 38.28). Smoking alone had 3.15 (1.40 to 8.11). Occupational asbestos alone had 4.91 (0.78 to 28.02), which was not statistically significant and was based on only 8 controls and 4 patients.
  • A further analysis used a comparison group with neither asbestos exposure nor smoking. Against it, smoking combined with extraoccupational asbestos exposure had an odds ratio of 8.42 (2.77 to 30.58). Smoking combined with occupational exposure had 13.50 (4.40 to 51.40).
  • Among occupational exposures, only asbestos was significantly associated with idiopathic RPF. Chemicals, metallic elements, pesticides, silica and organic solvents were not.
  • Among smokers and former smokers combined, cumulative smoking was greater in patients than in controls: median 31 pack-years versus 20 pack-years.
  • Two patients, both with documented occupational exposure, had pleural plaques compatible with asbestosis.
• The authors' conclusion: The authors concluded that reported asbestos exposure and smoking were strong risk factors for idiopathic RPF in this study. They also concluded that combined exposure to asbestos and smoke had a multiplicative effect on risk compared with single exposures.
• Limitations the authors state:
  • Exposure assessment was based only on retrospective, questionnaire-based occupational histories. Participants may have had difficulty recalling and quantifying exposure to specific agents.
  • Few patients were exposed to asbestos without smoking, so the study's ability to assess the effect of asbestos independently of smoking was very limited.
  • The control participants may not represent the population from which the patients came.
  • The sample was too small to explore whether asbestos exposure was linked to a specific form of the disease.

Topics

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

Related studies

• Asbestos exposure as a risk factor for retroperitoneal fibrosis — T. Uibu, P. Oksa, et al. (2004)
• Idiopathic retroperitoneal fibrosis: prospective evaluation of incidence and clinicoradiologic presentation — E.F.H. van Bommel, I. Jansen, et al. (2009)
• Idiopathic retroperitoneal fibrosis: an update for nephrologists — V. Raglianti, G.M. Rossi, et al. (2021)
• Asbestos and idiopathic retroperitoneal fibrosis — J.C. Boulard, T. Hanslik, et al. (1995)
• Retroperitoneal fibrosis and asbestosis--a plausible association? — R.D. Swartz (2015)
• Occupational and environmental risk factors for idiopathic pulmonary fibrosis in Australia: case-control study — M.J. Abramson, T. Murambadoro, et al. (2020)

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