title: Register-based studies of cardiovascular disease.
abstract: BACKGROUND
  The use of the unique personal identification number in the Nordic database systems enables the researchers to link the registers at the individual level. The registers can be used for both defining specific patient populations and to identify later events during follow-up. This review gives three examples within cardiovascular epidemiology to illustrate the use of the national administrative registers available to all researchers upon request.
  
  
  RESULTS
  The hospitalisation rate of acute myocardial infarction (AMI) was expected to be increased and case-fatality rate to decrease when the diagnostic criteria were changed in 2000. Linkage of national registers found a relative increase in hospitalisation rate of 14% while the case-fatality rate was unaffected. The pharmacological treatment of AMI patients was evaluated by linkage of administrative data. The use of evidence-based treatment increased significantly over time and adherence to treatment was high. Finally, use of specific nonsteroidal antiinflammatory drugs by healthy subjects was associated with a dose-dependent increase in cardiovascular risk.
  
  
  CONCLUSIONS
  The nationwide registers have proven very useful in monitoring the hospitalisation rate and treatment of cardiovascular disease. The risk of unmeasured factors affecting the results calls for cautious interpretation of the results.
authors.affiliation: National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark. stabil@dadlnet.dk
authors.forename: Steen Z
authors.initials: SZ
authors.lastname: Abildstrøm
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
authors.forename: Mette
authors.initials: M
authors.lastname: Madsen
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000009:adverse effects; D002318:Cardiovascular Diseases / Q000188:drug therapy / Q000453:epidemiology* / Q000401:mortality; D003718:Denmark / Q000453:epidemiology; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D019317:Evidence-Based Medicine; D005500:Follow-Up Studies; D006801:Humans; D009203:Myocardial Infarction / Q000188:drug therapy / Q000401:mortality; D010343:Patient Admission / Q000706:statistics & numerical data; D012042:Registries / Q000592:standards; D012307:Risk Factors; D012959:Socioeconomic Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal