RESUMO
Relative changes in disease incidence for different population groups can shed light on two questions: if they can be linked to groups exposed to contrasting types or intensities of intervention in a disease prevention program, they provide a way to assess the program's effectiveness; if they can be linked to groups with different levels of risk factors, they can provide information on the etiological relationships upon which prevention programs can be based. Sweden's registers and databases are reviewed as potential sources of cancer incidence data. In principle, these data may be used to evaluate the Stockholm Cancer Prevention Programme if "place of residence" is a sufficiently valid indicator of exposure to intervention. Through record linkage, the effect of socioeconomic status can be examined and controlled for. For etiological studies, differential changes in cancer incidence between geographical areas can be linked to, for example, local changes in diet, although data on this may be limited. However, given the "prospective" design and the expected lag between habit change and effect on morbidity, the sizes of the groups and the length of the period studied will have to be very substantial.
