This variable is only available in MAP.

Intradaily variability is a measure of circadian rhythm disturbance. The variable is measured using a portable actigraph: AX3 (2020-present), GENEActiv (2018-2020), Actical (2005-2018). See the Actigraphy category description for detailed information on each device. Participants are asked to wear the actigraph 24 hours per day for up to 10 days.

High intradaily variability may indicate daytime napping and/or nighttime arousals. See reference for calculation.

Note: Data is available for participants with at least one actigraphic recording of at least 7 consecutive days' duration.