To be included in the study a participant had to be an American Indian from one of the four tribes living on one of eight contiguous reservations, between the age of 18 and 70, and to be mobile enough to be transported from their home by van to the General Clinical Research Center (GCRC) of The Scripps Research Institute (TSRI). The protocol for the study was approved by the Institutional Review Board of TSRI, the scientific advisory committee of the GCRC, and the Indian Health Council, a tribal review group overseeing health issues for the reservations where the recruitments were undertaken.
