This variable is only available in MAP and MARS.

Presence of possible REM sleep behavior disorder (RBD) is measured using a question adapted from the Mayo Sleep Questionnaire (MSQ). Participants are asked to respond "yes" to the following question if the described event has occurred at least three times:

Have you ever been told that you appear to "act out your dreams" while sleeping (punched or flailed arms in the air, shouted or screamed)?

(Note: Very few participants report possible RBD.)