The research participants were 460 men and women aged 60e95 years. All participants were residents of, users of or visitors to the study recruitment sites; demonstrated no overt signs of psychosis or dementia (based on a cursory screening procedure) and were able to complete the study assessment battery (with assistance, if necessary). All prospective participants completed the informed consent process prior to study entry. Participants were recruited from 21 sites in the greater Los Angeles area, including 9 senior activity centres, 11 senior housing residences and 1 graduated care retirement community. Recruitmentstrategies included providingsign-upbooths, giving presentations at meetings and social events and distributing flyers and posters. Recruitment was undertaken in two successive cohorts to reduce temporal influences on study outcomes, overcome logistical difficulties, minimise interactions among participants and allow adjustments in ethnic stratification. Individuals in cohort 1 (n¼205) entered the study between November 2004 and June 2005, whereas those in cohort 2 (n¼255) entered the study between March and August 2006. The study protocol was approved by the Institutional Review Board at the University of Southern California prior to participant recruitment and conformed to the principles of the Declaration of Helsinki. Furthermore, the study was monitored by a five-member data safety monitoring board.