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.

Key terms Denmark; disease hotspot; disease mapping; malignant mesothelioma; mesothelioma; population-based study; rare disease; spatial analysis

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