Table 1 Key actigraphy variables and actigraphy measures in WORK-A
Metric types | Measure | Definition |
|---|---|---|
Key actigraphy variables | Time in bed (TIB) | The average time elapsed between the start time and the end time of a given rest interval (representing time spent in bed/at rest/attempting to sleep) in minutes |
Total sleep time (TST) | The total number of minutes within a given rest interval that have been scored as sleep by the sleep interval (representing time when sleep is occurring) detection algorithm | |
Sleep onset latency (SOL) | The time required for sleep to start after initiating the intent to sleep. The time, in minutes, between the start of a given rest interval and the onset of sleep as scored by the sleep interval detection algorithm | |
Wake after sleep onset (WASO) | The total number of minutes scored as wake within a given sleep interval | |
Sleep efficiency (SE) | The percentage of time spent in bed sleeping. Scored as TST/TIB multiplied by 100 | |
Actigraphy measures in Walter Reed Army Institute of Research Operational Research Kit-Actigraphy (WORK-A) | All intervals actigraphy measures | TIB, TST, SOL, WASO and SE averaged across all sleep intervals |
Major interval actigraphy measures | TIB, TST, SOL, WASO and SE averaged across only major sleep intervals (sleep intervals lasting longer than 3 h) | |
Minor interval actigraphy measures | TIB, TST, SOL, WASO and SE averaged across only minor sleep intervals (sleep intervals lasting between 15 min and 3 h) | |
Daily actigraphy measures | TIB, TST, SOL, WASO and SE combined for all sleep intervals within a 24-h period, then averaged across days worn | |
Sleep midpoint | Halfway point between the time of sleep onset and final awakening | |
Time worn | Number of minutes or days that device was worn | |
Daily sleep intervals (DSI) | The average number of sleep intervals recorded across all days worn | |
DSI bedtime (s) | Average start time for a sleep interval by DSI number within a 24-h period | |
DSI waketime (s) | Average end time for a sleep interval by DSI number within a 24-h period | |
Soldier sleep below minimum (SSBM) | Number of days during wear that participant slept less than a researcher-specified number of hours |