Adherence
The Sleep Regularity Index (SRI) and Interdaily Stability (IS) are sensitive to sleep fragmentation (awakenings) and napping, whereas Standard Deviation (StDev) and Composite Phase Deviation (CPD) are not sensitive to these factors.
If you want to assess sleep irregularity caused by waking up during the night or taking naps, use the Sleep Regularity Index (SRI) or Interdaily Stability (IS). Do not use Standard Deviation (StDev) or Composite Phase Deviation (CPD), as these metrics will ignore fragmentation and napping, giving you a false sense of regularity.
IS and SRI (but not StDev and CPD) are sensitive to napping and awakenings.
Why this rating
Based on large-scale simulations with systematic variation of parameters, providing high theoretical validity.
Source
Measuring sleep regularity: theoretical properties and practical usage of existing metrics
Dorothee Fischer et al. · SLEEP · 2021
DOI 10.1093/sleep/zsab103
More from this paper
- Overall metrics (StDev, IS) overestimate sleep regularity when based on study lengths of 7 days or less, whereas consecutive metrics (SRI, CPD) are more stable but require larger sample sizes.Strong
- Social Jet Lag (SJL) measures weekly differences in sleep timing (workdays vs. free days) and is insensitive to day-to-day variability.Good
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