26 Estimates are available for different basic categories such as gender, birth cohort, municipality and region in Denmark.
Four controls were matched to each case by date of birth and municipality of residence for a total of 9484 controls (1 : 4).
The links in the first step were considered correct, while all further links were checked manually for consistency in data fields, spelling mistakes in initials, date of birth, and municipality.
To follow-up on mortality, we developed a multi-stage, deterministic record-linkage between the cohort and the regional mortality registry for the years 2006-2007 using two match keys: first by full name, gender, date of birth and municipality of birth (step 1) and secondly by tax identification number (step 2).
In Denmark, a registry-based case control study (without subject participation) for cases diagnosed during 1976 1991 found elevated odds ratios for lymphoid leukaemia in children resident at birth in municipalities within the lowest decile of mean gross income, but no association for residence at diagnosis, or for individual SES measured by parental occupation (Raaschou-Nielsen et al, 2004).
We randomly selected for each case four controls from the general population, by extracting these referents from the municipal databases of residents matched for year of birth, sex and municipality of residence to each case, and using historical databases of residents according to the year of diagnosis.
Selection of participants in these studies was usually based on year of birth and residence (municipality or county).
Selection of participants in the studies was usually based on year of birth and residence (municipality or county).
Three controls per case were randomly selected from the computerised national population register matched by (closest) date of birth, gender and municipality of residence.
