I am exploring ways to assess (past) delirium in a large cohort study in the healthy general population spanning a wide age range. Re-assessments will take place in 3- to 4-year intervals. While delirium (and its association with cognitive decline/ neurodegenerative disease) is obviously an intriguing research question, I am concerned with the validity of its retrospective assessment in the general population. Are there any good (and preferably validated) self-report screening questions?