The evolution of an epidemic: age-period-cohort modelling of mesothelioma in Casale Monferrato, 1990-2021, with projections to 2042

Our plain-English summary of The evolution of an epidemic: age-period-cohort modelling of mesothelioma in Casale Monferrato, 1990-2021, with projections to 2042, by M. Giraldo, D. Zugna, E. Migliore, et al (Environmental Health, 2025).

The study

• Authors: M. Giraldo, D. Zugna, E. Migliore, J.P. Ramos-Bonilla, M. Maule
• Journal: Environmental Health
• Published: 2025;24(1):79
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: In Italy, the area of Casale Monferrato in the Piedmont Region has experienced a high burden of malignant mesothelioma (MM) due to environmental contamination from Eternit, the country's largest asbestos-cement plant, which operated from 1907 to 1986. The severity of the health impact led to the area's designation as a Site of National Interest (SIN) for environmental and health concerns. Despite the 1992 asbestos ban, the MM epidemic persists, driven by the disease's long latency. Using data from the Piedmont Malignant Mesothelioma Registry (RMM), we describe MM trends in Casale Monferrato's SIN from 1990 to 2021 and project future incidence through 2042 using Age-Period-Cohort (APC) models.

Methods: Incidence rates (1990-2021) were estimated as smooth functions of age and calendar time using APC models with restricted cubic splines. Projections through 2042 were made using three approaches: (1) spline-unrestricted, (2) spline-restricted, and (3) constraint-based approach. Performance was evaluated by predicting 2010-2021 rates using data up to 2010 and comparing predicted to observed cases. Sensitivity to the number and position of spline knots was assessed.

Results: Between 1990 and 2021, 1,282 pleural MM cases (731 men, 551 women) aged 35-96 were recorded in the Casale Monferrato SIN. Occupational exposure was reported in 61% of men and 21% of women. Non-occupational exposures, including environmental and familial exposures, were common in women (58%) than in men (22%). Incidence increased with age up to 85-90 years, and with birth cohort up to 1945 (154 and 105 per 100,000 in men and women, respectively), then declined. Rates increased over time by period until the mid-2010s and began to decrease thereafter. All approaches projected a slow but steady decline, with case numbers by 2035 returning to early 1990s levels. By 2042, incidence is estimated at 31 per 100,000 in men (8 cases) and 34 per 100,000 in women (9 cases).

Conclusions: The three approaches yielded consistent results, predicting extinction of the MM epidemic curve around mid-century. However, the health burden will persist over the next two decades, highlighting the need for sustained environmental health surveillance.

© 2025. The Author(s).

In plain English

This study used the Piedmont mesothelioma registry to describe pleural mesothelioma among people aged 35 and older in the Casale Monferrato Site of National Interest, around Eternit's former asbestos-cement factory. The authors fitted age-period-cohort models to 1990 to 2021 cases and projected to 2042 with three approaches. The registry recorded 1,282 cases (731 men, 551 women). Occupational exposure was reported for 61% of men and 21% of women. Non-occupational sources, including environmental and familial, were reported for 22% of men and 58% of women. In men the rate rose from 60 per 100,000 (1990 to 1999) to 97 (2010 to 2019). In women it rose from 37 (1990 to 1999) to 69 (2020 to 2021; another table gives 45). All approaches projected a decline. By 2042, best-fitting models estimated 8 cases in men (31 per 100,000; 95% CI 14 to 62) and 9 in women (34; 95% CI 16 to 65). The authors concluded the epidemic would decline gradually over 20 years but remain a significant public health burden for many years. Projections for women were less certain.

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 registry study: descriptive analysis of incidence plus age-period-cohort statistical modelling, with projections to 2042 using three approaches (spline-unrestricted, spline-restricted, constraint-based)
• Who was studied: 1,282 pleural malignant mesothelioma cases (731 men, 551 women) aged 35 and older, recorded from 1990 to 2021 in the Piedmont Registry of Malignant Mesothelioma within the Casale Monferrato Site of National Interest (48 municipalities, Piedmont, Italy); 66% were residents of the municipality of Casale Monferrato
• Exposure: Asbestos from the Eternit asbestos-cement factory in Casale Monferrato, which operated from 1907 to 1986, and from asbestos waste used by residents. The article does not name fiber types for this plant. Cases were classified by registry exposure source: occupational, familial, environmental, other, non-exposed, not determined, or to evaluate.
• Main results:
  • Among men, 61% reported occupational asbestos exposure and 22% were attributed to non-occupational sources.
  • Among women, 21% were associated with occupational exposure and 58% with non-occupational sources.
  • In men, the incidence rate was 60 per 100,000 (157 cases) in 1990 to 1999 and 97 per 100,000 (269 cases) in 2010 to 2019.
  • In women, the text and Table 2 give an incidence rate of 37 per 100,000 (117 cases) in 1990 to 1999 and 69 per 100,000 (27 cases) in 2020 to 2021.
  • Table 6 gives a different observed rate for women in 2020 to 2021, for the same 27 cases: 45 per 100,000 (95% CI 30 to 66).
  • By birth cohort, the highest rate in men was 154 per 100,000 among those born 1930 to 1939.
  • By birth cohort, the highest rate in women was 105 per 100,000 in the 1920 to 1929 birth cohort.
  • In men, the modelled period effect showed peaks in 2002 and 2014, followed by a decline from 2015 onward.
  • In men, observed incidence peaked in 2016 with 40 cases, an incidence rate of 154 (95% CI 104 to 198) per 100,000.
  • Judged against observed 2010 to 2021 cases, the spline-restricted approach predicted best for men and the constraint-based approach predicted best for women.
  • For men, all models projected a decline from an observed 101 per 100,000 in 2015 to 2019 to 16, 31 and 11 per 100,000 in 2042 (spline-unrestricted, spline-restricted and constraint-based, respectively).
  • For men in 2042, the best-fitting spline-restricted model projected 8 cases, an incidence rate of 31 per 100,000 (95% CI 14 to 62).
  • Men were projected to return to the 1990 level of 10 cases a year by about 2038, an incidence rate of 38 per 100,000 (95% CI 18 to 70) among people aged 35 and older.
  • For women, the rate was projected to fall from 76 per 100,000 in 2015 to 2019 to 23 (spline-unrestricted) or 57 (spline-restricted) per 100,000 in 2042.
  • For women, the constraint-based approach projected 9 cases in 2042, an incidence rate of 34 per 100,000 (95% CI 16 to 65).
  • By 2042, projections estimated 8 cases among men (31 per 100,000) and 9 among women (34 per 100,000), aged 35 and older.
• The authors' conclusion: The authors concluded that all projections point to a gradual decline of the mesothelioma epidemic curve over the next 20 years in the Casale Monferrato area, but that the epidemic will remain a significant public health burden there for many years.
• Limitations the authors state:
  • Mesothelioma is rare and hard to diagnose, especially in women, whose incidence rates varied more over time.
  • Changes over time in diagnostic practices and case reporting may have affected detection and classification of cases. The authors judged these factors unlikely to explain the trends.
  • Projections for women were more sensitive to model settings (number of knots), probably because there were fewer cases among women and more variable rates.
  • The authors used a classical age-period-cohort model rather than more advanced approaches such as Bayesian models.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Casale Monferrato, Eternit, Asbestos-Cement, Latency, Incidence, Occupational Exposure, Non-Occupational Exposure.

Related studies

• Cancer mortality and incidence of mesothelioma in a cohort of wives of asbestos workers in Casale Monferrato, Italy — D. Ferrante, M. Bertolotti, et al. (2007)
• A cohort study on mortality among wives of workers in the asbestos cement industry in Casale Monferrato, Italy — C. Magnani, B. Terracini, et al. (1993)
• Mesothelioma Incidence Rates in Australia since 1982: Exploring Age, Period, and Cohort Effects and Future Projections — K. Walker-Bone, M.A. Goodwin, et al. (2025)
• Increased risk of malignant mesothelioma of the pleura after residential or domestic exposure to asbestos: a case-control study in Casale Monferrato, Italy — C. Magnani, P. Dalmasso, et al. (2001)
• Psychological Distress after a Diagnosis of Malignant Mesothelioma in a Group of Patients and Caregivers at the National Priority Contaminated Site of Casale Monferrato — M. Bonafede, A. Granieri, et al. (2020)
• Para-occupational exposures to asbestos: lessons learned from Casale Monferrato, Italy — L.T. Stayner (2016)

Browse more research in Environmental Health, or return to medical research.