Attrition and Generalizability of Cognitive Aging Studies - A Population-Based Perspective
The number of elderly people suffering from cognitive impairment is expected to increase substantially along the population aging. In addition to the health concern for those affected, this may also cause a greater demand on our health care systems. Longitudinal studies where individuals are followed over a long time period on their cognitive performance have become central for studying cognitive aging and identifying modifiable risk and preventive factors. However, such studies face a difficulty from the fact that especially older participants tend to decline continued participation. Ignoring attrition may result in an overestimation of cognitive performance and moreover bias the contribution of risk factors on cognitive aging. While implications and adjustment for attrition on estimates of cognitive function is an active filed of research, selection before assessment is less well studied. Although determining the extent and consequences of different inclusion mechanisms are crucial for establishing generalizability of results beyond the study sample. In the proposed project we will identify possible inclusion mechanism and study how estimates of cognitive performance are influenced by attrition prior to assessment. The combination of data from a longitudinal study on cognition, health, and aging (the Betula study) and Swedish register data will provide unique opportunities to study possible inclusion mechanisms and their implications.