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Table 3 Parameters reported in studies of Rest–Activity Rhythms: additional details

From: An evidence map of actigraphy studies exploring longitudinal associations between rest-activity rhythms and course and outcome of bipolar disorders

Cosinor model (parametric)
Midline estimating statistic of rhythm (MESOR) Estimates the arithmetic mean of the values throughout the 24-h period
 Amplitude Distance from the rhythmic mean to the peak or trough of a mathematical model
 Acrophase Time interval during which the highest values are expected
Nonparametric approach
 Interdaily stability Quantifies the degree of resemblance between the activity patterns on individual days; ranges from 0 to 1 and may typically be about 0.6 for healthy adults
 Intradaily Variability Quantifies the fragmentation of periods of rest and activity; ranges from 0 to 2 and typically is < 1 for healthy adults, with higher values indicating a more fragmented rhythm
 L5 Average of the activity values for the 5 least active consecutive hours in the 24-h cycle
 L5 Onset Onset time of the five most restful consecutive hours
 M10 Average of the activity values for the 10 most active consecutive hours in the 24-h cycle
 M10 Onset Onset time of the 10 most active consecutive hours
 Amplitude Difference between M10 and L5
 Relative Amplitude Calculated by dividing AMP by the sum of L5 and M10; ranges from 0 to 1, with higher values indicating higher amplitude of the rhythm
Sleep quantity analysis
(reported as Individual Mean values or Intra-Individual Variability e.g. SD, RMSSD)
 Time in bed (TIB)
(Lights Off (LO))
Difference between the get-up time and bedtime
(Lights Off: time bedroom lights are turned off is reported in some therapy studies)
 Total sleep time (TST) Duration of the sleep episode, calculated on the actual time of sleep start and sleep end
 Sleep latency (SOL) Difference between time in bed and the actual time the monitored subject starts sleeping
 Mean activity (MA) Number of movements within specified epoch (usually 1 min)
 Number of awakenings longer than 5 min (NA > 5) Number of awakenings longer than 5 min
 Wake after sleep onset (WASO) Wake time (min) after sleep onset
 Sleep efficiency (SE %) Percentage of effective sleep during time in bed
 Fragmentation Index
(FI %)
% of sleep continuity/discontinuity. It is calculated as the amount of time associated with movement (restlessness) during the sleep period expressed as a percentage
Putative Circadian Phase Measures (derived from Sleep quantity analysis data)
 Sleep Onset Time is the clock time (HH:MM) of the first epoch scored as sleep in each main rest interval
 Sleep Offset Mean sleep offset time is the clock time (HH:MM) of the last epoch scored as sleep in each main rest interval
 Sleep midpoint Calculated as the midpoint between sleep onset and sleep offset
 Sleep Regularity Index (SRI) This is defined as the percentage probability of a person being asleep (or awake) at any two time points 24 h apart
  1. Cosinor model descriptions from Nelson et al (1979); nonparametric approach descriptions from Van Someren et al (1997). Sleep quantity analysis variables and descriptions as from Natale et al (2009), Krane-Gartiser et al. (2019) and Bei et al (2016)
  2. IS quantifies regularity in activity (overall variability in a time-signal after averaging across days) & IV quantifies fragmentation; some argue that SRI best quantifies how rapidly sleep patterns change between consecutive days