Update of predictions of mortality from pleural mesothelioma in the Netherlands. (Original Article).

Publication: Occupational and Environmental Medicine

Publication Date: 01-JAN-03

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COPYRIGHT 2003 British Medical Association

Aims: To predict the expected number of pleural mesothelioma deaths in the Netherlands from 2000 to 2028 and to study the effect of main uncertainties in the modelling technique.

Methods: Through an age-period-cohort modelling technique, age specific mortality rates and cohort relative risks by year of birth were calculated from the mortality of pleural mesothelioma in 1969-98. Numbers of death for both sexes were predicted for 2000 to 2028, taking into account the most likely demographic development. In a sensitivity analysis the relative deviation of the future death toll and peak death number were studied under different birth cohort risk assumptions.

Results: The age-cohort model on mortality 1969-98 among men showed the highest age specific death rates in the oldest age group (79 per 100 000 person-years in the age group 80-84 years) and the highest relative risks for the birth cohorts of 1938-42 and 1943-47. Among men a small period effect was observed. The age-cohort model was considered the best model for predicting future mortality. The most plausible scenario predicts an increase in pleural mesothelioma mortality up to 490 cases per year in men, with a total death toll close to 12 400 cases during 2000-28. However, using different assumptions this death toll could rise to nearly 15 000 in men (20% increase). Mortality among women remains low, with a total death toil of about 800 cases, It is predicted that the total death toll in the period 2000-28 is 44% lower than previous predictions using mortality data from l969 to 1993.

Conclusion: Adding five recent years of observed mortality in an age-cohort model resulted in a 44% lower prediction of the future death toll of pleural mesothelioma. A statistically significant period effect was observed, possibly influenced by initial asbestos safety guidelines in the 1970s and introduction of the ICD-10 codification.

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In 1960 Wagner et al reported the first conclusive association between asbestos exposure and pleural mesothelioma. (1 2) Mesothelioma affects mainly older men who in their youth were exposed to asbestos in the workplace. Its incidence in industrialised countries is about 5-50/million/year (male to female ratio between 5:1 and 11:1). The average latency period between first exposure to asbestos and diagnosis is 30 to 40 years, but shorter as well as longer latency periods have been observed; the longest latency periods were reported among women with possible household exposure. (2-4) Since the 1960s, mesothelioma has gained interest worldwide as a result of its increasing incidence, its ominous prognosis, and medicolegal issues. (5)

During the 1990s, forecastings of mesothelioma mortality in several developed countries were made based on mortality data before 1995. (6-11) They estimated a rise in fatal cases until 2010-20, after which a fast decline is expected because of asbestos bans. These projections used generalised linear models to calculate future deaths and to explain separate effects of age, year of birth (that is, cohort effect), and/or year of death (that is, period effect). For the Netherlands an increase from 300 pleural mesothelioma deaths in 1995 to approximately 960 around 2025 was predicted, with a fast decline after 2030. (6) A similar projection for Western European countries for the period 1995-2029 suggested an increase in the Netherlands to around 950 cases in the period 2020-25. (9) Since results of these analyses are sensitive to small changes in age specific mortality and birth cohort risks, it was expected that the inclusion of most recent mortality data may change previous predictions. The first preventive meas ures on asbestos use in the Netherlands were introduced in the mid-1970s. (12 13) Hence, it is of interest to evaluate whether the inclusion of data from 1994 to 1998 has a perceivable influence on the pleural mesothelioma mortality.

The objective of this paper is to predict the expected number of deaths from 2000 to 2028 and to conduct a sensitivity analysis in order to study the influence of changes in model assumptions on the prediction.

METHODS

Subjects

Statistics Netherlands (CBS) provided the latest mortality figures of pleural cancer and mesothelioma between 1969 and 1998, yearly age distributions of the Dutch population from 1949 to 1998, and estimations of Dutch population growth from 2000 to 2030. Standard extrapolation demographic techniques were applied for the latter figures. The Netherlands Cancer Registry provided the morbidity figures of pleural mesothelioma between 1989 and 1997. Pleural cancer was defined using the International Classification of Diseases and Related Health Problems (ICD). For the period 1969-78, ICD-8 163.0 pleural cancer was used, for 1979-95, ICD-9 163 pleural cancer, and from 1996 onwards, pleural mesothelioma as ICD-10 C450. We assumed cases of pleural cancer to be pleural mesothelioma on a ratio 1:1 for the time span 1979-95. In some countries it has been shown that a substantial porportion of deaths coded 163 are not pleural mesothelioma and a correction factor was applied for predictions in Western Europe. (7 9 14) Howe ver, because in the Dutch Cancer Registry 80-90% of all diagnoses were histologically confirmed, and the total numbers in the Cancer Registry and the Mortality Registry did...

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