The Influence Of Occupational And Environmental Asbestos Exposure On The Incident Of Malignant Mesothelioma In Connecticut

Our plain-English summary of The Influence Of Occupational And Environmental Asbestos Exposure On The Incident Of Malignant Mesothelioma In Connecticut, by H.C. Lewinsohn, J.W. Meigs, M.J. Teta, et al (1980).

The study

• Authors: H.C. Lewinsohn, J.W. Meigs, M.J. Teta, J.T. Flannery
• Published: Biological Effects Of Mineral Fibres (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 30, Pp. 655-660 (1980)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002178. The article is still under copyright, so we describe it here rather than post it.

In plain English

This preliminary report re-examined malignant mesothelioma cases in the Connecticut Tumor Registry from 1935 to 1977, looking at occupational and environmental asbestos exposure and possible diagnostic errors. The authors collected data on 229 mesothelioma cases, 38 other pleural tumours, their spouses, and 605 controls. The crude incidence rate was 2.2 per million. Age-adjusted rates rose for both sexes, rapidly for males from about 1960. In a model of pleural mesothelioma for 1955-1977, using odds ratios to approximate relative risks, people alive in 1975-1977 had 3.5 times the risk of those alive in 1955-1964 (confidence interval 2.25 to 5.48), and males had 3.0 times the risk of females (95% confidence interval 2.10 to 4.22). However, 56% of all tumour cases studied were not autopsied. For malignant pleural tumours diagnosed after 1954, a statistical analysis separating mesotheliomas from other pleural tumours by age, sex, survival time, stage and number of tumours produced 60% misclassification, which the authors said suggested possible misdiagnosis. The authors concluded that diagnostic reliability remained seriously in question, and a case review was under way. No results on asbestos exposure were reported.

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: Preliminary registry-based study: descriptive epidemiology of tumour registry cases (1935-1977), with case-control comparison and statistical (logistic regression) modelling for 1955-1977
• Who was studied: 229 malignant mesothelioma cases identified by the Connecticut Tumor Registry (pleura 147, peritoneum 33, other or unknown sites 49) plus 38 other pleural tumours, 1935-1977; their spouses; and 605 controls, a random sample of Connecticut decedents aged 20 to 98 years (1955-1977)
• Exposure: Occupational and environmental asbestos exposure, assessed from medical records, death certificates and City Directories. Cases with occupations linked in the literature to mesothelioma were selected for study. No fiber types are named, and no exposure results are reported.
• Main results:
  • The crude incidence rate for mesothelioma in Connecticut was 2.2 per million for 1935-1977.
  • Age-adjusted incidence rates increased for both sexes, with a rapid rise from about 1960 for males.
  • Of the 229 mesothelioma cases, 195 were reported after 1954. Mean age at diagnosis was 59 years.
  • Cases clustered in dense urban areas. Ten cases were reported (1955-1977) in an area where shipyards are located, five of them between 1975 and 1977.
  • Pleural mesothelioma, 1955-1977 model, with relative risks approximated by odds ratios: persons alive in 1975-1977 had a 3.5 times greater risk than those alive between 1955 and 1964 (confidence interval 2.25, 5.48).
  • Pleural mesothelioma risk was 1.5 times greater in each ten-year age group (from 45-54 onward) than in the preceding one. The confidence interval is printed as 2.13; 1.31.
  • Males had 3.0 times the risk of pleural mesothelioma of females (95% confidence interval 2.10, 4.22).
  • A sizeable proportion (56%) of the cases were not autopsied. Table 1's total row covers all 267 tumours (mesotheliomas and other pleural tumours). Autopsy rates were low for pleural tumours other than mesothelioma (35%) and for mesotheliomas at other or unknown sites (33%). The unknown-site group had a mean age of only 52 years.
  • The analysis covered malignant pleural tumours diagnosed after 1954. A discriminant function analysis tried to separate mesotheliomas from other pleural tumours using age, sex, survival time, stage and number of tumours, and it yielded 60% misclassification. The authors said this suggested possible misdiagnosis.
• The authors' conclusion: The authors concluded that the results suggest possible misdiagnosis and that a case review was advisable. Although incidence rose rapidly from 1955 to 1977, they found a serious question of diagnostic reliability. Only after diagnostic adjustment and identification of occupationally exposed subjects might it be possible to determine the role of environmental asbestos exposure, if any.
• Limitations the authors state:
  • The descriptive and analytical results assume complete and accurate case identification.
  • A sizeable proportion (56%) of cases were not autopsied.
  • Information from 1935-1954 was inadequate for case-control comparisons, owing to missing occupational and clinical data and lack of awareness of mesothelioma.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Mesothelioma, Cancer Registry, Incidence, Pleural Mesothelioma, Odds Ratio, Relative Risk, confidence interval.

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