Non-parametric circadian rhythm analysis (NPCRA)

Computes the standard non-parametric circadian rhythm analysis variables from an actigraphy recording. All variables are derived from the 24-hour activity profile following Van Someren et al. (1999) and Marler et al. (2006).

Usage

compute_npcra(x, epoch_s = NULL, L5_hours = 5, M10_hours = 10)

Arguments

x

A zeitr_recording as returned by read_actigraphy(), or a data frame / tibble with at least datetime and activity columns.

epoch_s

numeric(1). Epoch duration in seconds. If NULL (default), estimated automatically from the median inter-epoch interval.

L5_hours

numeric(1). Width of the least-active window in hours. Default is 5.

M10_hours

numeric(1). Width of the most-active window in hours. Default is 10.

Value

A one-row tibble with columns participant_id, IS, IV, RA, L5, L5_onset, M10, M10_onset, n_days, n_epochs.

Details

The following variables are computed:

IS

Interdaily stability — consistency of the 24 h activity pattern across days (range 0–1; higher = more stable).

IV

Intradaily variability — fragmentation of the rest-activity rhythm (>= 0; higher = more fragmented).

RA

Relative amplitude — contrast between the most active 10 h window (M10) and least active 5 h window (L5) (range 0–1).

L5

Mean activity during the least active 5 h window.

L5_onset

Clock time of the L5 window midpoint (hh:mm).

M10

Mean activity during the most active 10 h window.

M10_onset

Clock time of the M10 window midpoint (hh:mm).

References

Van Someren, E. J. W., Lijzenga, C., Mirmiran, M., & Swaab, D. F. (1997). Long-term fitness training improves the circadian rest-activity rhythm in healthy elderly males. Journal of Biological Rhythms, 12(2), 146–156. doi:10.1177/074873049701200206

Marler, M. R., Gehrman, P., Martin, J. L., & Ancoli-Israel, S. (2006). The sigmoidally transformed cosine curve: a mathematical model for circadian rhythms with symmetric non-sinusoidal shapes. Statistics in Medicine, 25(22), 3893–3904. doi:10.1002/sim.2466

Van Someren, E. J. W., Swaab, D. F., Colenda, C. C., Cohen, W., McCall, W. V., & Rosenquist, P. B. (1999). Bright light therapy: Improved sensitivity to its effects on rest-activity rhythms in Alzheimer patients by application of nonparametric methods. Chronobiology International, 16(4), 505–518. doi:10.3109/07420529908998724

Examples

if (FALSE) { # \dontrun{
rec   <- read_actigraphy("recordings/P001.txt")
npcra <- compute_npcra(rec)
npcra
} # }