Time trends and spatial patterns in the mesothelioma incidence in Slovenia, 1961-2014

Our plain-English summary of Time trends and spatial patterns in the mesothelioma incidence in Slovenia, 1961-2014, by V. Zadnik, M. Primic Zakelj, K. Jarm, et al (European Journal of Cancer Prevention, 2017).

The study

• Authors: V. Zadnik, M. Primic Zakelj, K. Jarm, T. Zagar
• Journal: European Journal of Cancer Prevention
• Published: 2017;26 Joining forces for better cancer registration in Europe:S191-S196
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We aimed to explore the temporal and spatial variations in mesothelioma incidence in Slovenia for the last 50 years and, among these, to evaluate the consequences of asbestos usage. The incidence data from the population-based Cancer Registry of Republic of Slovenia for the period 1961-2014 were analysed. The data of asbestos imported to Slovenia were used as a proxy for asbestos exposure in manufacturing areas. Log-linear joinpoint regression and age-period-cohort Poisson models were used in the time-trend analysis. The mesothelioma maps were produced according to the method of local standardized incidence ratio estimates and are presented together with the map of Slovenian major asbestos-exposed locations. The maximum value of the asbestos import curve corresponds to the peak of mesothelioma curve exactly 30 years later. Both increases before the peak are comparable in time interval and steepness. The highest mesothelioma risk was detected for the cohort born between 1940 and 1944. In maps, the mesothelioma clusters manifest around known asbestos sources predominantly in the years 1980-1990, but in the last few years, the geographical distribution is more dispersed. The data from our long-existing population-based cancer registry provide a good insight into the on-going mesothelioma epidemic in Slovenia. Our results imply that the mesothelioma peak has already been reached in Slovenia. In the future, new cases will emerge more randomly throughout the country.

In plain English

The authors analysed all mesothelioma cases recorded in Slovenia's population-based cancer registry from 1961 to 2014, describing trends over time and mapping where cases lived. Because Slovenia produced no asbestos of its own, yearly amounts of imported asbestos were used as a stand-in for exposure in manufacturing areas. By the end of 2014 the registry held 766 cases, 546 (71.3%) of them in men. Of all cases, 83.0% were pleural and 15.7% peritoneal mesothelioma. Age-standardized incidence rose on average 7.2% a year over 40 years, most steeply from 1998 to 2003, and was stable after 2004. The authors reported that the 1973 peak in asbestos imports appeared to correspond to the mesothelioma peak 30 years later. In the Goriska region, where 90% of imported asbestos was manufactured, incidence was consistently 3 to 5 times the national rate. Risk was highest for people born in 1940 to 1944. The authors concluded that the peak has already been reached but that incidence will not fall as steeply as asbestos use did. They noted that before 1980 doctors were discouraged from diagnosing mesothelioma.

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 cancer registry analysis of time trends (joinpoint regression and age-period-cohort Poisson models) and geographical mapping (local standardized incidence ratio method), compared with national asbestos import data
• Who was studied: All mesothelioma cases recorded in the Cancer Registry of Republic of Slovenia, 1961 to 2014: 766 cases, 546 (71.3%) of them men
• Exposure: Annual amounts of raw asbestos imported to Slovenia, used as a proxy for exposure in manufacturing areas. Locations of major asbestos point sources, chiefly the Salonit Anhovo cement-asbestos factory in the Goriska region, were also mapped.
• Main results:
  • Over the 40 years after 1970, age-standardized incidence rates in Slovenia increased on average by 7.2% each year
  • In 2005 to 2009 there were 1.5 mesothelioma cases per 100 000 inhabitants in Slovenia overall, and 2.3 per 100 000 in men
  • Of all cases, 83.0% were pleural mesothelioma and 15.7% were peritoneal mesothelioma
  • Women accounted for 171 of 636 pleural mesothelioma cases (26.8%) and 47 of 120 peritoneal mesothelioma cases (39.2%)
  • Nationally, the steepest increase was from 1998 to 2003 (APC 13.5; 95% CI 5.7 to 20.6)
  • After 2004, the national mesothelioma trend was stable (APC -0.4)
  • The authors reported that the 1973 peak in asbestos imports appeared to correspond to the mesothelioma peak exactly 30 years later
  • In the Goriska region, where 90% of imported asbestos was manufactured, mesothelioma incidence was consistently 3 to 5 times higher than nationally
  • On the maps, a cluster of cases was constantly evident in the western part of the country, in the Goriska region on the Italian border
  • In the age-period-cohort analysis, mesothelioma risk was highest in the 1940 to 1944 birth cohorts and decreased in younger generations
  • The age-adjusted log-linear trend (drift) increased by 21.2% per 5 years
  • The male to female ratio increased from 2.3 in 1985 to 1989 to 3.4 in 2005 to 2009
• The authors' conclusion: The authors concluded that their results imply the mesothelioma peak has already been reached in Slovenia. They also anticipated that incidence will not follow the steep decrease of the asbestos import curve, and that new cases will appear more randomly throughout the country.
• Limitations the authors state:
  • Before 1980, doctors were discouraged from diagnosing mesothelioma, even in exposed workers
  • Geocoded population data were not available for earlier periods, so the background population was mirrored for earlier years
  • Because of the limited number of cases, 5-year moving averages were used
  • Younger age groups and earlier periods were excluded from the age-period-cohort analysis because there were too few cases in them
  • Wide confidence intervals for the decreasing risk in younger birth cohorts indicate large uncertainty

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Cancer Registry, Asbestos Exposure, Standardized Incidence Ratio (SIR), Mesothelioma Cluster.

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