Sustained-Inactivity-Bout Sleep Scoring from the z-Angle

Scores each epoch sleep ("S") or wake ("W") from the z-angle by the van Hees et al. (2015) sustained-inactivity-bout rule: an interval with no arm-posture change exceeding angle_thresh degrees for at least time_thresh minutes is sustained inactivity (sleep). The output has the same shape as sleep.cole.kripke, so it feeds sleep.regularity.index, lids and the rest consumers directly. Intersect it with rest.spt via sleep.from.spt.

Usage

sib.vanhees(anglez, angle_thresh = 5, time_thresh = 5, epoch_length = 5)

Arguments

anglez: Numeric z-angle (degrees) per epoch.
angle_thresh: Posture-change threshold in degrees (default 5).
time_thresh: Minimum sustained-inactivity duration in minutes (default 5).
epoch_length: Epoch length in seconds (default 5).

Value

Character vector of "S"/"W", one per epoch. A day with fewer than 10 posture changes is scored all "S" (sustained inactivity, to be gated by the SPT window and wear time).

References

van Hees VT, Sabia S, Anderson KN, Denton SJ, Oliver J, Catt M, Abell JG, Kivimaki M, Trenell MI, Singh-Manoux A (2015). “A novel, open access method to assess sleep duration using a wrist-worn accelerometer.” PLoS ONE, 10(11), e0142533. doi:10.1371/journal.pone.0142533 .

Examples

# A long still stretch scores as sustained inactivity (sleep)
set.seed(1)
anglez <- c(rnorm(3000, -60, 0.02), rnorm(3000, 0, 20))   # still, then active
table(sib.vanhees(anglez, epoch_length = 5))
#> 
#>    W 
#> 6000