Variable Details

Available Studies
MAP
Scaled? 
Not Scaled
Variable Type 
Longitudinal
Variable Name 
iv
Categories
Sleep and Circadian Rhythms, Actigraphy

Intradaily variability
Actical measure - Intradaily variability (MAP only)

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.

Publications

Witting W, Kwa IH, Eikelenboom P, Mirmiran M, Swaab DF. Alterations in the circadian rest-activity rhythm in aging and Alzheimer's disease. Biological psychiatry. 1990 Mar 15; 27 (6):563-72. PubMed PMID: 2322616; PubMedCentral PMCID: