Age-Period-Cohort Analysis of Mesothelioma: Flat Incidence Trends for Males Entering US Workforce After 1972 - Abstract
Abstract This study investigates the hypothesis that US government regulations on occupational asbestos exposures starting in 1972 caused a cohort inflection point after which mesothelioma incidence was flat for males subsequently entering the workforce. An age-period-cohort analysis of the SEER 8 cancer registries (1975-2019) was conducted using five-year intervals of age, calendar period, and birth cohort to evaluate US male incidence of all mesothelioma, as well as pleural, or peritoneal mesothelioma. Work cohort year was defined as birth cohort plus 18 years. Average percent change analysis was used to further evaluate period effects. Age- and period-adjusted work cohort rate ratios (RR) for all mesothelioma, and for pleural mesothelioma, were significantly elevated for work cohorts between 1920 and 1972 with subsequent decreased/flat trends. Similar age- and period-adjusted analysis of peritoneal mesothelioma showed non-significantly elevated work cohort RR between 1920 and 1954 with flat/not elevated incidence trends for work cohorts after 1954. Average percent change trend analyses showed statistically significant period effects on incidence rate trends for all mesothelioma and pleural mesothelioma, but not peritoneal mesothelioma; mesothelioma groups demonstrated significant longitudinal age trends. The cohort of US males first entering the workforce after 1972 shows no increased incidence of pleural mesothelioma. These trends may be related to the impacts of occupational asbestos regulations that took effect in 1972 in addition to plausible threshold dose-dependent risks from chrysotile asbestos which continued to be used through the 1990s. In contrast, US male workers first entering the workforce after the mid-1950s showed no increased risk of peritoneal mesothelioma which has been predominantly associated with amphibole asbestos exposures used in shipbuilding in the era of World War
II. The flattening of work cohort mesothelioma rates after 1972 suggests the era of prominent risks from occupational asbestos exposure has ended; continuing incidence may be
attributable to non-asbestos etiologies