Group leaders
Maria Glymour
University of California, San Francisco, USA


Elizabeth Rose Mayeda
University of California, San Francisco, USA

Selection issues in dementia research arise from several sources: differential attrition of enrolled participants, differential survival of enrolled participants, and differential enrollment, either due to refusal to participate or differential survival up to the moment of study initiation. Each of these processes can bias effect estimates. Spurious associations between the putative risk factor and cognitive decline or dementia can occur when selection processes are related to cognitive status and the exposure of interest (or their determinants). The bias is not necessarily towards the null (i.e., which would tend to mask an association), and can sometimes reverse the direction of association (i.e., making harmful exposures appear protective or protective exposures appear harmful).