Actigraphy-derived sleep estimates in one-month-old infants are strongly influenced by the choice of activity threshold and time-window duration, with threshold choice having a strong effect on total sleep duration and five-minute windows identifying 50% fewer sleep bouts than three-minute windows.
Key Findings
Results
Activity threshold choice had a strong effect on total sleep duration in one-month-old infants.
Estimated sleep duration ranged from 15.9 to 18.1 hours per day across all tested configurations.
Higher activity thresholds (20 or 40 counts) systematically inflated sleep duration compared to lower thresholds.
Threshold effect on total sleep duration was statistically significant (p < 0.001).
A threshold of 15 counts yielded the most coherent estimates relative to pediatric literature values for sleep duration (9.3–20 h).
Analyses used linear mixed-effects models across 49 breastfed infants aged 24.9 ± 3.6 days monitored for seven days.
Results
Time-window length had minimal influence on total sleep duration but strongly affected the number and duration of detected sleep bouts.
Window length had minimal influence on total sleep duration estimates.
Five-minute windows identified 50% fewer sleep bouts compared to three-minute windows (p < 0.001).
Five-minute windows produced substantially longer bout durations compared to three-minute windows (p < 0.001).
Poisson regression was used to assess the number of sleep bouts across configurations.
Results
The choice of five-minute versus three-minute time windows substantially altered the distribution of sleep period durations.
The W5-T15 configuration increased the proportion of sleep periods lasting 45–60 minutes compared to W3-T15 (7.8% vs. 5.2%, p < 0.001).
The W5-T15 configuration reduced the proportion of shorter sleep periods compared to W3-T15 (57.5% vs. 76.9%, p < 0.001).
Shorter windows increased sensitivity to brief transitions, whereas longer windows reduced fragmentation artefacts and yielded more consolidated sleep periods.
The focused comparison between W3-T15 and W5-T15 configurations was used to specifically assess sleep bout duration differences.
Methods
The study sample consisted of 49 breastfed infants monitored at home using actigraphy with parental sleep reports used to correct artefactual immobility.
Infants had a mean age of 24.9 ± 3.6 days at the time of monitoring.
Sleep was recorded using a MotionWatch8 actigraph with raw 60-second epochs.
Raw epochs were cross-checked with parental sleep reports to correct artefactual immobility.
Monitoring was conducted at home for seven days.
Six parameter configurations were tested: 3- or 5-minute windows combined with thresholds of 15, 20, or 40 counts.
Results
Plausibility screening based on pediatric literature values supported the use of a 15-count threshold as the most appropriate configuration for one-month-old infants.
Plausibility screening used published pediatric literature values for sleep duration ranging from 9.3 to 20 hours.
Higher thresholds (20 and 40 counts) produced sleep duration estimates that inflated beyond plausible ranges.
The threshold of 15 counts yielded the most coherent estimates relative to established normative values.
These findings underscore the need for standardized parameter settings in early-infancy actigraphy.
What This Means
This research suggests that when using wrist-worn motion sensors (actigraphs) to measure sleep in very young infants, the technical settings chosen by researchers can dramatically change the results. The study tested six different combinations of two key settings — how long a time window is used to classify sleep versus wakefulness (3 or 5 minutes), and how much movement is allowed before a period is counted as awake (thresholds of 15, 20, or 40 movement counts) — in 49 breastfed babies around one month old who wore the devices at home for a week. The estimated total daily sleep ranged from about 16 to 18 hours depending purely on which settings were used, with higher movement thresholds making babies appear to sleep more. Using a 5-minute window instead of a 3-minute window cut the number of detected sleep episodes in half and made individual sleep periods appear much longer.
The practical implication is that two studies using the same type of device but different settings could produce very different pictures of infant sleep, making it difficult to compare findings across research studies or clinical assessments. The researchers found that a threshold of 15 movement counts produced estimates most consistent with what is known from the pediatric literature about how long newborns actually sleep. The 5-minute window tended to smooth over brief wake periods and produced more 'consolidated' looking sleep, which may or may not reflect reality.
This research suggests that the field needs standardized, agreed-upon parameter settings before actigraphy can be reliably used to track infant sleep across different studies or clinical contexts. Without such standards, comparisons between studies are unreliable, and conclusions about infant sleep health drawn from actigraphy data may depend more on methodological choices than on the infants' actual sleep behavior.
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Halbouty Z, Youbi L, Bach V, Delanaud S, Haraux E, Chardon K. (2026). The impact of actigraphy parameter choices on sleep estimates in one-month-old infants.. Sleep medicine. https://doi.org/10.1016/j.sleep.2026.109046