In additional analyses in the HRS, we predicted several cognitive phenotypes. Total Cognition is the sum of four cognitive measures measured in waves 3 through 10: an immediate word recall task, a delayed word recall task, a naming task, and a counting task. Verbal Cognition measures the subject’s ability to define five words. To evaluate changes over time, we also studied wave-to-wave changes in Total Cognition and Verbal Cognition. Our next cognitive outcome, Alzheimer’s, is an indicator variable equal to 1 for subjects who report having been diagnosed with Alzheimer’s disease, and 0 otherwise. Since the HRS data are longitudinal, the unit of analysis for our 4 cognitive outcomes is a person-year. For these analyses, because an individual took the cognitive tests at different ages, in our set of controls we replaced our person-specific age variable with age at assessment (which differs for an individual across the cognitive outcomes); we also clustered all standard errors at the person level.
