K. Otsuka, Y. Ichimaru and T. Yanaga, “Studies of Arrhythmias by 24-Hour Polygraphic Recordings: Relationship between Atrioventricular Block and Sleep States,” American Heart Journal, Vol. 105, No. 6, 1983, pp. 934-940. doi:10.1016/0002-8703(83)90393-9

has been cited by the following article:

• TITLE: Double Crossover Points in the DFA of Heartbeats in Patients with Sleep Apnea

  AUTHORS: Midori Ichimaru, Yuhei Ichimaru, George B. Moody, Kuniaki Otsuka

  KEYWORDS: Sleep Apnea; DFA (Detrended Fluctuation Analysis); Scaling Exponent; Crossover Points; Heartbeats

  JOURNAL NAME: International Journal of Clinical Medicine, Vol.3 No.7, January 2, 2013

  ABSTRACT: Cardiovascular and cerebrovascular events have been observed during night-time associated with periodic breathing including sleep apnea and Cheyne-Stokes respiration. Early detection and treatment is important to reduce night-time events. We clarified the characteristics of the dynamic nature of heartbeats associated with periodic breathing by using detrended fluctuation analysis (DFA). We analyzed heartbeats in eight recordings from the MIT-BIH Polysomnographic database. We observed two crossover points and defined three scaling exponents, β1 (n ≤ 40 beats), β2 (50 ≤ n ≤ 200), and β3 (251 ≤ n ≤ 1584). Compared with β1 (1.21 ± 0.13) and β3 (0.92 ± 0.16), scaling exponent β2 (0.62 ± 0.16) showed the statistically lowest value (p 0.05). And there was a negative relationship between the scaling exponent β2 and apnea/hypopnea index (p 0.05). These results indicate that DFA analysis of heartbeats may be useful for the early detection of sleep associated breathing disorders including sleep apnea and its severity.