Poster Session #2 Abrupt increase in heart rate during the transition from non-REM sleep to wakefulness and its utility for estimating sleep stages Gih Sung Chung a , Jeong Su Lee a , Su Hwan Hwang a , Do-Un Jeong b , Kwang Suk Park a a Department of Biomedical Engineering, Seoul National University College of Medicine, Seoul, Republic of Korea b Center for Sleep and Chronobiology, Seoul National University Hospital, Seoul, Republic of Korea Since fluctuation of heart rate (HR) reflects the activation of the autonomic nervous system (ANS) and ANS activity varies during sleep according to the depth of sleep, HR variation is known to reflect the change of sleep stages. However, it has been very difficult to estimate the sleep stage transitions beyond a certain degree of accuracy with HR only. If we can estimate sleep stage transition with higher accuracy by HR only, it will be clinically very useful. Therefore, we devised a method for estimating the sleep stage transition from non-REM sleep to a state of wakefulness based on the abrupt HR increase. Electrocardiogram data were collected from 12 normal volunteers (8 males and 4 females; age 27 ± 2.34 years) during the whole night polysomnography (PSG). Then, we detected the episodes of abrupt HR increase for the whole night. Signal processing was used to compensate for the slow fluctuation of HR during sleep and a threshold was applied for the detection of abrupt HR increase. We compared the result with the sleep stage findings read by the experts from PSG with the standard method. In contrast to other transitions among sleep stages, transitions from any non-REM sleep stage to wakefulness showed significant HR increase. The accuracy of the detection of transition to wakefulness from non-REM sleep was 97±0.02%, using HR signal only. However, HR did not remain in the increased state through the wakefulness, but returned to the baseline rate slowly with adaptation. Therefore, we found it difficult to estimate the extended wakefulness state with HR only. During REM sleep, with HR generally higher than in non- REM sleep, we also found it difficult to estimate the transition to wakefulness using the HR increase criteria. In this study, we found that there tends to be an abrupt HR increase in the transition of non- REM sleep stage to wakefulness and it could be reliably used to estimate the transition. The observed HR increase between non-REM sleep and wakefulness seems to be caused by sudden sympathetic activation from the parasympathetic dominance. doi:10.1016/j.ijpsycho.2010.06.159 Sleep/wake detection: A comparison between three wearable instruments Nelleke C. van Wouwe a , Pierre J.L. Valk a , Bertil Veenstra b a TNO Defence, Security and Safety, Soesterberg, The Netherlands b TGTF, Utrecht, The Netherlands Fatigue, intense physical exercise, or extreme environmental conditions negatively impact physical and cognitive performance. Effective physiological monitoring, such as sleep monitoring, may assist with the creation of adequate interventions to prevent these negative consequences or to provide an indication for recovery. The current study compared three wearable instruments with respect to their effectiveness in predicting sleep. Additionally, we investigated the added value of heart rate variability, as reflected by accelerometer signals, to estimate sleep duration. Participants were asked to wear three physiological monitoring instruments for two nights: a chest International Journal of Psychophysiology 77 (2010) 288–342 0167-8760/$ – see front matter Contents lists available at ScienceDirect International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho