Effects of Between- and Within-Subject Variability on Autonomic Cardiorespiratory Activity during Sleep and Their Limitations on Sleep Staging: A Multilevel Analysis

Table 2

Description of the seven explanatory effects (with exclusion of sleep stage effects) on cardiorespiratory activity considered in this study.

Effect	Description
Overall between-subject effect
Demographic effect	Fixed effect, variability in age, gender, and BMI between subjects
Centering (physiological) effect	Fixed effect, variability in overnight mean level between subjects
Between-subject time effect	Random effect, variability in time of night between subjects
Between-subject physiological effect	Random effect, variability in physiology between subjects
Overall within-subject effect
Within-subject time effect	Fixed effect, variability in time of night within subjects
Within-subject physiological effect	Random effect, variability in physiology within subjects
Cross-interaction effect
Demographic-related time effect	Fixed effect, demographic-related variability in time of night