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. Author manuscript; available in PMC: 2015 Dec 1.
Published in final edited form as: Early Hum Dev. 2014 Oct 23;90(12):885–890. doi: 10.1016/j.earlhumdev.2014.09.005

Table 1.

Circadian rhythm parameters derived from mother and infant actigraphy recordings.

Fixed Period 24 hour Cosinor Model Parameters:
Mesor pattern Midpoint level or mean activity count of the fitted 24 hour rhythm
Magnitude Difference between the model fit peak value and the mesor; the amount of change from mesor to peak of the cycle
Acrophase Decimal clock time of fitted cycle peak; the time of highest activity in the cycle
R2 GOF Goodness of Fit Index, R-square of the within-subject model fit; measure of fit with 24-hour period, variance explained by the fitted curve
Non-Parametric Circadian Rhythm Analysis (NPCRA) Descriptors:*
L5 midpoint Decimal clock time for the midpoint of the L5 block; timing of lowest activity
M10 midpoint Decimal clock time for the midpoint of the M10 block; timing of highest activity
Amplitude Difference between L5 and M10 segments average levels; difference in activity level of highest and lowest periods
IS Interdaily Stability, normalized index of the similarity of activity patterns across days, strength of coupling with 24-hour environment; values from 0 to 1.0 with 1.0 indicating exact coupling.
IV Intradaily Variability, measure of the fragmentation of the rest/activity pattern; frequency of transitions in activity, values from 0 (near perfect sine wave) to ≥ 2 (noise or ultradian rhythm)
*

reference: Van Someren EJ, Swaab DF, Colenda CC, Cohen W, McCall WV, Rosenquist PB. Bright light therapy: improved sensitivity to its effects on rest-activity rhythms in Alzheimer patients by application of nonparametric methods. Chronobiol Int. 1999;16(4):505-18.