Attrition in Longitudinal Data is Primarily Selective with Respect to Level Rather than Rate of Change

An important question in longitudinal research is whether the individuals who discontinue participation differ in their level of, or their change in, cognitive functioning relative to individuals who return for subsequent occasions.Performance in five cognitive domains was examined in nearly 5000 participants between 18 and 85 years of age who completed between one and five longitudinal occasions.Little or no differences in cognitive performance...