title: Comparisons of Portable Sleep Monitors of Different Modalities: Potential as Naturalistic Sleep Recorders.
abstract: BACKGROUND
  Humans spend more than one-fourth of their life sleeping, and sleep quality has been significantly linked to health. However, the objective examination of ambulatory sleep quality remains a challenge, since sleep is a state of unconsciousness, which limits the reliability of self-reports. Therefore, a non-invasive, continuous, and objective method for the recording and analysis of naturalistic sleep is required.
  
  
  OBJECTIVE
  Portable sleep recording devices provide a suitable solution for the ambulatory analysis of sleep quality. In this study, the performance of two activity-based sleep monitors (Actiwatch and MTN-210) and a single-channel electroencephalography (EEG)-based sleep monitor (SleepScope) were compared in order to examine their reliability for the assessment of sleep quality.
  
  
  METHODS
  Twenty healthy adults were recruited for this study. First, data from daily activity recorded by Actiwatch and MTN-210 were compared to determine whether MTN-210, a more affordable device, could yield data similar to Actiwatch, the de facto standard. In addition, sleep detection ability was examined using data obtained by polysomnography as reference. One simple analysis included comparing the sleep/wake detection ability of Actiwatch, MTN-210, and SleepScope. Furthermore, the fidelity of sleep stage determination was examined using SleepScope in finer time resolution.
  
  
  RESULTS
  The results indicate that MTN-210 demonstrates an activity pattern comparable to that of Actiwatch, although their sensitivity preferences were not identical. Moreover, MTN-210 provides assessment of sleep duration comparable to that of the wrist-worn Actiwatch when MTN-210 was attached to the body. SleepScope featured superior overall sleep detection performance among the three methods tested. Furthermore, SleepScope was able to provide information regarding sleep architecture, although systemic bias was found.
  
  
  CONCLUSIONS
  The present results suggest that single-channel EEG-based sleep monitors are the superior option for the examination of naturalistic sleep. The current results pave a possible future use for reliable portable sleep assessment methods in an ambulatory rather than a laboratory setting.
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Fumi
authors.initials: F
authors.lastname: Masuda
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Yukiyoshi
authors.initials: Y
authors.lastname: Sumi
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Faculty of Education, Shiga University , Hikone , Japan.
authors.forename: Masako Hasegawa
authors.initials: MH
authors.lastname: Ohira
authors.affiliation: Department of Systems Science, Kyoto University , Kyoto , Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Fujiwara
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science , Otsu , Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanemura
authors.affiliation: Department of Psychiatry, Shiga University of Medical Science, Otsu, Japan; Department of Sleep and Behavioral Sciences, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kadotani
keywords: activity recorders; polysomnography; portable sleep monitors; single channel EEG; sleep estimation