MORGAM Manual

Definition and selection of cohorts

Each MORGAM Participating Centre (MPC) can have one or several cohorts in the study. The cohorts are defined as the subsets of random survey samples on geographically defined populations, on which data are available on daily cigarette smoking, blood pressure and blood total cholesterol. A prerequisite for inclusion of the cohort to the study is that there is a follow-up for coronary heart disease (CHD) and stroke mortality with high coverage.

The cohorts will be identified by the MPC, Reporting Unit (RU), which is the smallest geographical population unit which will be identified from the study data, and the cohort identification. There may be several cohorts in the same RU, for example corresponding to different sample surveys conducted at different times.

Especially when cohorts are based on different sample surveys in the same population, some individuals may have been selected in more than one cohort. As one individual cannot be a member of several cohorts, the MPC has to include such individuals into only one cohort. The choice of the cohort must not depend on the follow-up information, and it is recommended that priority is given to cohorts where DNA was collected at the baseline.

Most of the cohorts are defined in the population surveys of the WHO MONICA Project, but also other cohorts can be accepted. The cohorts are followed up for all mortality, with the cause of death specified. Furthermore, many of the cohorts are expected to be followed up for non-fatal coronary events and strokes.

The decision on the acceptance of the cohorts to the study is made by the MORGAM Management Group (MMG), and the cohorts, together with the key identification information, will be listed in section Participating Centres and Cohorts of the MORGAM Manual.