Cole-Kripke Sleep/Wake Scoring

Classifies each epoch as sleep or wake from activity counts with the Cole-Kripke algorithm (Cole et al. 1992), validated for adults on one-minute epochs, with the optional Webster rescoring rules (Webster et al. 1982). Returns the per-epoch sleep_state that the regularity and locomotor-sleep metrics read (sleep.regularity.index, lids).

Usage

sleep.cole.kripke(
  counts,
  apply_rescoring = TRUE,
  epoch_length = 60,
  na_action = c("na", "wake", "zero")
)

Arguments

counts: Numeric vector of activity counts (vertical axis).
apply_rescoring: Apply Webster's rescoring rules (default TRUE).
epoch_length: Epoch length in seconds (default 60). The algorithm was validated on 60-second epochs; other lengths raise a warning.
na_action: How NA-count epochs appear in the output: "na" (default) emits NA, so non-wear gaps are not read as sleep; "wake" scores them wake; "zero" scores them from a zero count.

Value

Character vector of states, "S" (sleep) or "W" (wake), the same length as counts.

Details

The sleep index uses a seven-epoch window (four before, the current epoch, and two after): $$D = 0.001 (106 P_4 + 54 P_3 + 58 P_2 + 76 P_1 + 230 C + 74 N_1 + 67 N_2)$$ These are Cole's mean-activity-per-minute weights (Table 6, p.466); the $/100$ count scaling and the 300 cap are implementation conventions. An epoch is scored sleep when $D < 1$. Webster's rescoring then re-labels short sleep bouts that follow or are surrounded by sustained wake as wake.

References

Cole RJ, Kripke DF, Gruen W, Mullaney DJ, Gillin JC (1992). “Automatic sleep/wake identification from wrist activity.” Sleep, 15(5), 461–469. doi:10.1093/sleep/15.5.461 .

Webster JB, Kripke DF, Messin S, Mullaney DJ, Wyborney G (1982). “An activity based sleep monitor system for ambulatory use.” Sleep, 5(4), 389–399. doi:10.1093/sleep/5.4.389 .

Examples

# \donttest{
agd <- agd.counts(read.agd(example_agd(1), verbose = FALSE))
state <- sleep.cole.kripke(agd$axis1)
table(state)
#> state
#>    S    W 
#> 7641 2278 
# }