Epidemiologists in England & Wales often ascertain cancers from the National Health Service Central Register (NHSCR). NHSCR records everyone registered with a general practitioner and notes if a person dies. Since 1971, NHSCR have also noted cancer registrations. If researchers tell NHSCR the details of people in their studies, NHSCR will tell the researchers which of them have died or been registered with cancer.

In 1995, we asked NHSCR for details of all deaths from cancer and cancer registrations, (site and type codes and dates of diagnosis) among the 287,013 children in our Cumbrian birth cohort.