The cohort – the North Carolina Health Project (NCHP) research cohort –was developed by faculty of the University of North Carolina at Chapel Hill (UNC), in collaboration with the North Carolina Academy of Family Physicians, for the purpose of facilitating research on chronic disease and related health care problems commonly addressed in primary care settings.

During the initial cohort enrollment (16 practice sites, 2001), 7,687 adult patients had appointments at the study practices. Of these, 2,921 were not enrolled, largely because they refused study participation. The remaining 4,766 (62%) completed the enrollment questionnaire, of whom 4054 (85% of those completing the questionnaire; 53% of eligible subjects) consented to be included in the cohort (i.e., to be approached for additional studies).

In the second wave of cohort recruitment (five practice sites, 2004), 1935 new subjects were successfully enrolled (65.3 % of eligible patients). Of these, 1411 (72.9% of enrollees, and 47.6% of all eligible subjects) agreed to be contacted for further studies.