Experience of cohort formation and data collection in a retrospective cohort epidemiological study

Abstract

A retrospective cohort study was carried out to investigate the mortality of workers occupationally exposed to dust containing chrysotile asbestos fibers. In its chemical and physical properties, it differs from the fibers of other types of asbestos and is the only type of asbestos that is currently approved for use in many countries of the world. The members of the cohort are current and former employees who have worked for at least one year at the production sites of the complex of enterprises for the mining and enrichment of chrysotile asbestos (JSC "Uralasbest", Asbest, Sverdlovsk region) in the period from 01.01.1975 to 31.12.2010. Of the 35,837 members of the cohort, 12,729 (35.5%) people died (2,373 of them were malignant neoplasms of various localizations, including 10 mesotheliomas), 18,799 (52.5%) were alive at the end of the observation period (2015), and 4,309 people (12.0%) were censored by the end of 2015. The mean follow-up period was 21.7 years for men and 25.9 years for women. The average age at death was 59.4 years for men and 66.5 years for women. It is currently the world's largest cohort of workers in the field.