Explaining differences in incidence rates of pleural mesothelioma between Sweden and the Netherlands

Our plain-English summary of Explaining differences in incidence rates of pleural mesothelioma between Sweden and the Netherlands, by A. Burdorf, B. Järvholm, A. Englund (International Journal of Cancer, 2005).

The study

• Authors: A. Burdorf, B. Järvholm, A. Englund
• Journal: International Journal of Cancer
• Published: 2005;113(2):298-301
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In recent years in several countries a deceleration or leveling off of pleural mesothelioma rates has been observed. The impact of asbestos used was analysed by comparing a country with a relative modest incidence rate of mesothelioma (Sweden) and an early response to asbestos use with a country with one of the highest incidence rates of mesothelioma in Western Europe (The Netherlands). In Sweden the Cancer Register provided information on the annual incidence of pleural mesothelioma, whereas in The Netherlands mortality data were provided by Statistics Netherlands for the period 1969-2001. In The Netherlands among men the incidence rate was consistently higher (1.5-2 times) than in Sweden, whereas among women similar rates were observed. Assuming that none of the female cases was caused by occupational exposure to asbestos, minimum estimates of the etiologic fraction for occupational exposure to asbestos in men would be 82% in Sweden and 92% in The Netherlands. Possible explanations for the consistently higher incidence rates in the Netherlands than in Sweden include differences in exposure levels, the proportion of exposed subjects in the workforce and types of asbestos fibres used. Measures to decrease the exposure to asbestos seem to have decreased the risk of pleural mesothelioma in both countries among age groups below 60 years. This effect will result in a leveling off of the increase in pleural mesothelioma in both countries in the next decade.

In plain English

This study compared pleural mesothelioma trends in Sweden and the Netherlands, 1969 to 2001, at ages 25 to 84. Swedish data came from the Cancer Register. The Dutch Cancer Registry had full national coverage only from 1989, so Dutch figures came from death records. Among men, Swedish cases rose from 15 in 1969 (0.5 per 100,000 person-years) to 89 in 2001 (3.0); Dutch cases rose from 61 (1.8) to 313 (5.9). Dutch male rates averaged 1.7 times Swedish rates (range 1.5 to 2.1); age adjustment changed this only marginally. Rates in women were similar in both countries and stable. Assuming no female cases were work-related, the authors estimated that at least 82% (Sweden) and 92% (Netherlands) of male cases were due to occupational asbestos exposure. Male rates peaked in 1984 to 1988 at ages 45 to 49, then declined; ages 50 to 54 and 55 to 59 followed five and ten years later. The authors concluded that exposure-reduction measures seem to have lowered risk in men born in the late 1940s and later. They called the cause of the difference between the countries unclear.

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: Comparison of national register data on pleural mesothelioma trends in two countries: cancer registrations in Sweden and death records in the Netherlands. The data were analysed by age, period and birth cohort, with direct age standardization.
• Who was studied: Men and women aged 25 to 84 years, 1969 to 2001: cases in the Swedish Cancer Register, and deaths in mortality data from Statistics Netherlands
• Exposure: Historic national use of asbestos, measured as imports of raw asbestos, set against each country's regulations. Sweden's first regulation came in 1964, crocidolite was prohibited from 1975, and virtually all asbestos uses were prohibited in 1989. The Netherlands banned crocidolite in 1978 and banned all asbestos products in 1994. In both countries most imported asbestos was chrysotile.
• Main results:
  • Swedish men: cases rose from 15 in 1969 (0.5 per 100,000 person-years) to 89 in 2001 (3.0 per 100,000 person-years)
  • Dutch men, same period (death data): from 61 cases (1.8 per 100,000 person-years) to 313 cases (5.9 per 100,000 person-years)
  • Male rates in the Netherlands were consistently higher than in Sweden, with an average ratio of 1.7 (range 1.5 to 2.1)
  • The Swedish male rate stabilized at around 2.5 per 100,000 after 1989, while Dutch rates kept rising
  • Among women, rates were very similar in both countries and stable over time. Swedish women had 2 to 26 cases a year (0.07 to 0.80 per 100,000). Dutch women had 8 to 43 deaths a year (0.20 to 0.86 per 100,000).
  • Adjusting for differences in age structure only marginally affected the national rates
  • Among men under 60 in both countries, peaks came at staggered times. Men aged 45 to 49 had their highest rate in 1984 to 1988 and a decline afterward. The same pattern came 5 years later at ages 50 to 54 and 10 years later at ages 55 to 59.
  • The authors read this as a birth cohort effect: in both countries, men born 1935 to 1943 had higher rates than men born before or after
  • In 1999 to 2001 the rate in women was 0.5 per 100,000 person-years in both countries, against 2.8 in Swedish men and 5.9 in Dutch men. Assuming no female cases were occupational, the share of male cases due to occupational asbestos exposure was 82% in Sweden and 92% in the Netherlands. Assuming half of female cases were occupational, the shares were 91% and 96%.
  • In older Dutch men (over 60) rates kept rising in later periods. In Sweden the highest rates in these age groups were reached in 1984 to 1993 and then leveled off.
• The authors' conclusion: The authors concluded three things. Measures to decrease asbestos exposure seem to have decreased the risk of pleural mesothelioma in both countries among men born in the late 1940s and later. Occupational asbestos exposure contributed about 90% or more of cases in men in both countries. The male rate was about 1.5 to 2 times higher in the Netherlands, for reasons that are unclear. As possible explanations they suggested differences in exposure levels, in the proportion of exposed workers, or in fiber types. They said they could not rule out differences in crocidolite and amosite use.
• Limitations the authors state:
  • The Dutch Cancer Registry had complete national coverage only from 1989, so the authors used death data for the Netherlands instead of new-case data. They argued that death rates correspond reasonably closely to new-case rates because most patients die within a year.
  • Dutch deaths coded as pleural cancer in 1979 to 1995 were assumed to be pleural mesothelioma, one to one
  • For 1996 to 2001, Dutch pleural mesothelioma deaths had to be estimated, because most mesothelioma deaths were coded as unspecified mesothelioma
  • There was no information on the share of amphibole fibers in each country's asbestos imports
  • The proportion of exposed workers in each workforce could not be estimated reliably
  • The occupational share estimates rest on assumptions about women's cases and are regarded as minimum estimates

Topics

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

Medical terms in this study, explained in our Lexicon: Incidence, Pleural Mesothelioma, Mesothelioma, Occupational Exposure, Population Attributable Fraction (PAF).

Related studies

• Pleural mesothelioma in Sweden: an analysis of the incidence according to the use of asbestos — B. Järvholm, A. Englund, et al. (1999)
• Incidence and familial risk of pleural mesothelioma in Sweden: a national cohort study — J. Ji, J. Sundquist, et al. (2016)
• Mesothelioma incidence seems to have leveled off in Sweden — K. Hemminki, X. Li (2003)
• Occupation and mesothelioma in Sweden: updated incidence in men and women in the 27 years after the asbestos ban — N. Plato, J.I. Martinsen, et al. (2016)
• Asbestos exposure and differences in occurrence of peritoneal mesothelioma between men and women across countries — A. Burdorf, B. Järvholm, et al. (2007)
• Incidence, mortality and survival in malignant pleural mesothelioma before and after asbestos in Denmark, Finland, Norway and Sweden — K. Hemminki, A. Försti, et al. (2021)

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