Incidence trends of mesothelioma in Norway, 1965-1999

Asbestos exposure is considered to be the only important risk factor for malignant mesothelioma. The importation of asbestos to Norway increased after World War II and peaked in 1970. Stringent regulations took effect in 1977, and importation and use of asbestos practically ended in Norway in the late 1970s, until importation was prohibited in 1982. Our study aimed to analyze the incidence of mesothelioma in Norway according to temporal variation, to study the consequences of the use of asbestos and the asbestos ban effectiveness. An age-period-cohort model was used to analyze time trends for pleural mesotheliomas. From 1965-1999, the annual number of pleural mesotheliomas rose gradually both in males and females, and the highest annual number of pleural mesotheliomas was recorded in 1999 with 73 new cases diagnosed. The age-adjusted log linear drift of malignant mesothelioma of the pleura during the observation period rose 31.1% per 5 years among men and 15.9% among women. In 1995-1999, the age-adjusted incidence rate for men was 16.6 per million person-years for men and 2.3 for women. Cohort-specific risks increased for men born up to around 1935. After this the risks seem to stabilize. The rates were determined by age and by birth cohort. The delayed period effect of the asbestos regulation by the late 1970s will probably have its greatest effects on the mesothelioma rates around 2010.