title: Screening for obstructive sleep apnea by cyclic variation of heart rate.
abstract: BACKGROUND
  Despite the adverse cardiovascular consequences of obstructive sleep apnea, the majority of patients remain undiagnosed. To explore an efficient ECG-based screening tool for obstructive sleep apnea, we examined the usefulness of automated detection of cyclic variation of heart rate (CVHR) in a large-scale controlled clinical setting.
  
  
  RESULTS
  We developed an algorithm of autocorrelated wave detection with adaptive threshold (ACAT). The algorithm was optimized with 63 sleep studies in a training cohort, and its performance was confirmed with 70 sleep studies of the Physionet Apnea-ECG database. We then applied the algorithm to ECGs extracted from all-night polysomnograms in 862 consecutive subjects referred for diagnostic sleep study. The number of CVHR per hour (the CVHR index) closely correlated (r=0.84) with the apnea-hypopnea index, although the absolute agreement with the apnea-hypopnea index was modest (the upper and lower limits of agreement, 21 per hour and -19 per hour) with periodic leg movement causing most of the disagreement (P<0.001). The CVHR index showed a good performance in identifying the patients with an apnea-hypopnea index ≥15 per hour (area under the receiver-operating characteristic curve, 0.913; 83% sensitivity and 88% specificity, with the predetermined cutoff threshold of CVHR index ≥15 per hour). The classification performance was unaffected by older age (≥65 years) or cardiac autonomic dysfunction (SD of normal-to-normal R-R intervals over the entire length of recording <65 ms; area under the receiver-operating characteristic curve, 0.915 and 0.911, respectively).
  
  
  CONCLUSIONS
  The automated detection of CVHR with the ACAT algorithm provides a powerful ECG-based screening tool for moderate-to-severe obstructive sleep apnea, even in older subjects and in those with cardiac autonomic dysfunction.
authors.affiliation: Department of Medical Education, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. Hayano@med.nagoya-cu.ac.jp
authors.forename: Junichiro
authors.initials: J
authors.lastname: Hayano
authors.forename: Eiichi
authors.initials: E
authors.lastname: Watanabe
authors.forename: Yuji
authors.initials: Y
authors.lastname: Saito
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sasaki
authors.forename: Keisaku
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nomiyama
authors.forename: Kiyohiro
authors.initials: K
authors.lastname: Kawai
authors.forename: Itsuo
authors.initials: I
authors.lastname: Kodama
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sakakibara
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D017286:Polysomnography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult