Evaluation of Two Novel Methods for Infant Sleep Depth Measurements in Home Environment

Abstract Recently developed unobtrusive methods for at-home infant sleep monitoring can complement parental observations and support infant wellbeing by providing detailed information on overnight sleep patterns. However, further work is needed to understand how such methods capture variations in sleep depth and overall sleep structure in real-world environments. We compared automated assessments of whole-night sleep structure from two novel noninvasive systems designed for at-home use: an under-mattress sensor (Nucu) and a research-grade wearable device (NAPPA). Both provide a time course of sleep structure akin to a hypnogram, conceptualized as a calmness curve in Nucu and a sleep depth trend (SDT) in NAPPA. Simultaneous recordings were collected across 11 nights from four infants aged 3–10 months. Correspondence between outputs was evaluated using Spearman rank correlation (rho) and visual comparison of the time courses. Comparison of the calmness and SDT out-puts showed a very strong overall correlation rho = 0.85 (p < 0.001) in unselected whole-night data, and a nearly as high correlation during sleep-only time periods (rho = 0.81, p < 0.001). Although some night‑to‑night variability was present, correlations remained consistently high for both whole-night recordings (rho = 0.72–0.93, across nights) and the sleep-only periods (rho = 0.69–0.89, across nights). Likewise, the visual appearance of the whole-night sleep structure was comparable between systems. The strong agreement between the two methods suggests that both capture consistent information about sleep depth. Together with earlier validation of NAPPA device, the findings of the present work strengthen the evidence base for the development of feasible, non-invasive, and contactless monitoring of infant sleep depth in home environments.