The International Database of Ambulatory blood pressure in relation to Cardiovascular Outcome (IDACO): Protocol and research perspectives

Objectives: The International Database on Ambulatory Blood Pressure Monitoring (1993-1994) lacked a prospective dimension. We are constructing a new resource of longitudinal population studies to investigate with great precision to what extent the ambulatory blood pressure improves risk stratification. Methods: The acronym IDACO refers to the new International Database of Ambulatory blood pressure in relation to Cardiovascular Outcome. Eligible studies are population based, have fatal as well as nonfatal outcomes available for analysis, comply with ethical standards, and have been previously published in peer-reviewed journals. In a meta-analysis based on individual patient data, composite and cause-specific cardiovascular events will be related to various indexes derived by ambulatory blood pressure monitoring. The analyses will be stratified by cohort and adjusted for the conventional blood pressure and other cardiovascular risk factors. Results: To date, the international database includes 7609 patiens from four cohorts recruited in Copenhagen, Denmark (n =2311), Noorderkempen, Belgium (n= 2542), Ohasama, Japan (n =1535), and Uppsala, Sweden (n= 1221). In these four cohorts, during a total of 69 295 person-years of follow-up (median 9.3 years), 1026 patients died and 929 participants experienced a fatal or nonfatal cardiovascular event. Follow-up in five other eligible cohorts, involving a total of 4027 participants, is still in progress. We expect that this follow-up will be completed by the end of 2007. Conclusion: The international database of ambulatory blood pressure in relation to cardiovascular outcome will provide a shared resource to investigate risk stratification by ambulatory blood pressure monitoring to an extent not possible in any earlier individual study.