Detailed mapping of mesothelioma cases in Denmark to identify areas with elevated risk: a nationwide population-based study

Our plain-English summary of Detailed mapping of mesothelioma cases in Denmark to identify areas with elevated risk: a nationwide population-based study, by H.S. Christensen, R.H. Jensen, L.H. Nielsen, et al (Scandinavian Journal of Work, Environment & Health, 2025).

The study

• Authors: H.S. Christensen, R.H. Jensen, L.H. Nielsen, L.D. Bertelsen, C. Teglgaard, J.H. Bønløkke, M.T. Severinsen, M. Bøgsted
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 2025;51(5):449-453
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: Previous studies mapping pleural mesothelioma in Denmark have found that the risk varies between Danish regions. However, evaluating disease risk for such relatively large geographical units ignores any heterogeneity within the unit and can thus diminish more local spikes in risk, missing smaller areas of excess risk. In this study, we examined the distribution of pleural mesothelioma in Denmark on an unprecedented detailed scale, mapping cases to each of the Danish parishes.

Methods: We identified individuals diagnosed with pleural mesothelioma between 1990 and 2021 in the Danish Cancer Registry. Considering age- and sex-standardized incidence rate ratios (IRR), we used a conditional autoregressive random effects model to smooth IRR across parishes. Parishes with a smoothed parish-to-national IRR >1.25 or >2.0 with a posterior probability of >95% were flagged as parishes with an excess risk of pleural mesothelioma.

Results: We identified 3105 incident cases of pleural mesothelioma in the study period. A total of 74 and 14 parishes were flagged with IRR significantly above 1.25 and 2.0, respectively. These parishes had posterior mean smoothed IRR of 1.82-4.13.

Conclusions: We provided a detailed mapping of pleural mesothelioma cases in Denmark and found five distinct areas, each covering several parishes, with a significantly elevated risk. All these areas were in the proximity of previous asbestos-using industries.

In plain English

This short communication was a nationwide register study that mapped pleural mesothelioma across Denmark's 2141 parishes. From the Danish Cancer Registry, the authors identified 3105 Danish residents diagnosed between 1990 and 2021, 2618 of them male. Each person was placed in a parish by home address at diagnosis. The national incidence rate was 1.81 per 100 000 person-years. Because parish case counts were small, the authors used a statistical model that borrowed information from neighbouring parishes to smooth age- and sex-standardized rate ratios. They flagged parishes very likely (over 95% probability) to have rates more than 25% or more than 100% above the national rate. Seventy-four parishes in five areas met the first level, with smoothed ratios of 1.83 to 4.13. Fourteen parishes around Aalborg, Odense and Helsingør met the second, with ratios of 2.85 to 4.13. No Copenhagen-area parishes were flagged. The authors concluded that all five areas could be linked to previous asbestos-using industries. They noted that residence at diagnosis may not reflect where exposure happened, and that they did not study the reasons for the differences.

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: Nationwide population-based register study (short communication) mapping disease rates by parish, using a Bayesian spatial model (conditional autoregressive, Leroux) to smooth age- and sex-standardized parish-to-national incidence rate ratios. Parishes were flagged when the posterior probability of the ratio exceeding 1.25 or 2 was greater than 95%.
• Who was studied: All 3105 Danish residents diagnosed with pleural mesothelioma between 1 January 1990 and 31 December 2021, identified in the Danish Cancer Registry and assigned to one of 2141 Danish parishes by residential address at diagnosis.
• Exposure: Asbestos exposure was not measured. The study mapped place of residence at diagnosis. In the discussion, the authors related flagged areas to past local industries: shipyards, a large asbestos cement factory (Aalborg), a large producer of asbestos-containing brakes (Odense) and an oil refinery (Kalundborg). No fiber types are named.
• Main results:
  • Across Denmark, 3105 residents were diagnosed with pleural mesothelioma in 1990 to 2021, a national incidence rate of 1.81 per 100 000 person-years. 2618 (84%) were male.
  • 74 parishes were flagged with a smoothed rate ratio very likely above 1.25, and 14 parishes with a ratio very likely above 2.0.
  • The 14 parishes with rates more than double the national rate had posterior mean smoothed ratios of 2.85 to 4.13.
  • The 14 parishes were located in and around the cities of Aalborg, Odense and Helsingør.
  • The 74 parishes with rates more than 25% above the national rate had posterior mean smoothed ratios of 1.83 to 4.13. Beyond the three areas above, they included one parish near Kalundborg and one in Frederikshavn.
  • No parishes in the Copenhagen capital area were flagged at the chosen thresholds.
  • At diagnosis, the people in the study had on average lived at the same address for 27 years.
• The authors' conclusion: The authors concluded that detailed mapping found five distinct areas of Denmark with elevated pleural mesothelioma risk, all of which could be linked to previous asbestos-using industries (in the abstract: all were in the proximity of such industries).
• Limitations the authors state:
  • Mapping was based on residence at diagnosis. Because of the long latency between first asbestos exposure and disease, where people lived at diagnosis does not necessarily reflect where they were exposed.
  • Choosing a baseline rate other than the national rate, or other probability thresholds, may lead to different results.
  • The reasons for the geographical differences, including whether exposure was occupational or environmental, were not investigated.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleural Mesothelioma, Cancer Registry, Incidence.

Related studies

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• Risk of cancer among Danish utility workers--a nationwide cohort study — C. Johansen, J.H. Olsen (1998)
• Tuberculosis and risk of cancer: a Danish nationwide cohort study — D.F. Simonsen, D.K. Farkas, et al. (2014)
• Treatment patterns among patients with malignant pleural mesothelioma: An Italian, population-based nationwide study — A. Trama, C. Proto, et al. (2020)
• Incidence of lung cancer by histological type among asbestos cement workers in Denmark — E. Raffn, E. Lynge, et al. (1993)
• Occupational dust exposure and head and neck squamous cell carcinoma risk in a population-based case-control study conducted in the greater Boston area — S.M. Langevin, M.D. McClean, et al. (2013)

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