The registry of the new city was then contacted until the individual was located. Changes of residence were recorded in a database with the exact date of moving. In the case of death, date and city of death were provided by the local registry office. Cause of death was either ascertained through a record linkage system of the NRW regional statistical office or through the local health offices. The record linkage system has been described in detail by Klug and colleagues (2003). Local health offices provided an anonymous copy of the relevant death certificate. All copies of death certificates were then professionally coded at the Saarland Cancer Registry.
