The baseline examination of the 9,294 participants (2,104 in Bordeaux, 4,931 in Dijon, and 2,259 in Montpellier) started in March 1999 and ended in March 2001. In Bordeaux and Dijon, participants were first examined at home (interview, physical measurements and cognitive testing). Participants aged less than 85 years were then invited to the study centre for the completion of the other parts of the study protocol. In Montpellier, all participants were asked to attend a half-day examination at the study centre. Only those who refused or who were unable to attend were interviewed and tested at home. The baseline examination included carotid ultrasound examination in 6,612 participants aged less than 85 years and cerebral MRI in 3,442 participants aged less than 80 years. See Data Collection for details on available data.
Follow-up 1 and 2 (2001-2004)
Participants were interviewed for major medical and personal events, and were subjected to physical examination and cognitive testing. Participants who were screened positive for dementia or who reported a history of coronary heart disease or stroke were subject to further clinical examination. In Bordeaux and Dijon, at follow-up 2, a second MRI was given to participants who had been subjected to an MRI at baseline. Each follow-up examination included ascertainment, documentation, and validation of the main outcomes of the study - dementia, coronary heart disease, (CHD) and stroke - by outside panels of experts.
Follow-up 3 and following (2005-2012)
In 2005, a postal questionnaire was sent to all participants. Those who did not return the questionnaire were contacted and interviewed by telephone. The questionnaire focused on the occurrence of vascular events and major life events, such as admission to a nursing home.
The third wave of follow-up examinations started in 2006. In addition to the 3C core protocol, centre-specific ancillary studies involving the collection of new data were initiated: nutrition (COGINUT study in Bordeaux and Montpellier), ocular diseases (ALIENOR study in Bordeaux), vascular diseases and walking speed (COVADIS study in Dijon), auditory disorders (Montpellier), etc. Differences in study protocols led to slightly different study schedules. The follow-up of the 3C cohort is planned to terminate in 2012.