Dear NSRR developers,
Your efforts in maintaining the datasets are so valuable for the sleep study field. Thanks a lot for all the work you've accomplished.
I want to ask a question about the sleep stage annotations in the numom2b dataset. It seems they have only 2 classes: N2 and Awake. I am confused about it. Am I checking the wrong file or the annotations do only have two classes? How were the sleep stages annotated? Are the annotations based on EEG signals or other signals?
Best regards, Hao
nuMoM did not have EEG signals, so traditional sleep staging was not possible. The Stage 2 indicators you see in the annotation files represent the estimated sleep period. There is some description in the Flacco 2015 paper:
Level 3 sleep monitoring devices, as used in this study, do not record sleep directly (i.e. with EEG and electromyography signals). Therefore, sleep onset and offset and periods of prolonged wakefulness are identified by certified polysomnologists using information from both participant completed questionnaires on bed and wake times and the visualized patterns of heart rate, breathing pattern, movement and artifact. The sleep period is defined as the period between sleep onset and offset. Sleep onset is identified based on self-reported bedtime plus visualization of reduced signal artifact, decreased heart rate, regularization of breathing pattern, and stability of the position sensor (indicating a supine or lateral position). Conversely, sleep offset is identified by evidence of sustained movement artifact, changing position, increase in heart rate, and participant reported wake time. Following the initiation of sleep, segments of the study were excluded from analysis if significant movement or artifact occurred for a period of ≥ 20 minutes.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4410772/
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