Reliability of Actigraphy for the Assessment of Sleep and Circadian Rhythms in Rett and Related Syndromes.
Plan seven to ten nights of actigraphy for stable average sleep data in Rett, but double the span if you care about night-to-night variability.
01Research in Context
What this study did
Byiers et al. (2026) asked how many nights you need to record actigraphy before the numbers stay the same. They studied people with Rett and related syndromes. The team looked at both average sleep scores and night-to-night swings.
They used wrist-watch actigraphy for several weeks. Then they checked how stable each metric was across nights.
What they found
After seven to ten nights, average sleep numbers became reliable. Circadian rhythm scores stayed shaky even with longer recording.
Night-to-night variability was the least stable. If you want a steady picture of sleep range, you need more than ten nights.
How this fits with other research
Cohen et al. (2018) showed that night-to-night swings in actigraphy predict next-day problem behavior in low-functioning autism. Breanne’s work says those same swings are the least reliable metric in Rett. The two studies do not clash; they just flag that short samples can mislead you when you track variability.
Torelli et al. (2023) validated a heart-rate and breathing sleep tracker against gold-standard polysomnography in people with ID. Their positive finding supports using wearables, and Breanne adds the rule of thumb: give actigraphy at least a week before you trust the average.
Fyfe et al. (2007) built a video tool for Rett assessment. Breanne now gives sleep clinicians a similar reliability guide for actigraphy, filling the sleep side of the assessment shelf.
Why it matters
If you run sleep assessments for clients with Rett, record actigraphy for seven to ten nights before you write goals or make changes. Shorter runs can fool you with one rough night. Do not trust night-to-night swing numbers unless you have even more data. This simple schedule saves staff time and keeps treatment decisions honest.
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Set your actigraphy device to record for at least ten nights before the first data review meeting.
02At a glance
03Original abstract
PURPOSE: Actigraphy is being increasingly used to assess sleep and circadian rhythms among populations with intellectual and developmental disabilities and genetic syndromes, including Rett syndrome and related disorders, but the reliability of these measures in these populations is unclear. The primary purpose of the current study was to evaluate the impact of recording duration on the reliability of various measures of sleep and circadian rhythm in Rett and related syndromes. METHOD: Two 14-day recordings were collected between 4 and 12 weeks apart in a sample of 30 individuals (aged 2-36 years; 97% female). Reliability was estimated by calculating statistics based on 3, 5, 7, 10 or 13-14 nights of recording. RESULTS: Most measures of average sleep quality could be reliably estimated with 7-10 nights. Measures of night-to-night variability in sleep timing showed poor reliability at all recording durations, whereas night-to-night variability in sleep duration showed adequate reliability at 5-7 days of recording. The reliability of measures of circadian rhythm was highly variable. CONCLUSIONS: The results suggest that the optimal recording durations for actigraphy in this population vary based on the specific metrics of interest, but most can be measured reliably.
Journal of intellectual disability research : JIDR, 2026 · doi:10.1016/j.braindev.2007.04.001