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Fractal dimension of the sleep state waveform in obstructive sleep apnea

Fraktale Dimension der Wellenform von Schlafphasen bei obstruktiver Schlafapnoe

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Abstract

Question of the study

Sleep represents a complex interplay of biological processes. This study examines whether the dynamics of the sleep state changes exhibit fractal properties and the implications of such changes in obstructive sleep apnea.

Patients and methods

Overnight polysomnography data on 25 volunteers from a publicly available data set were analyzed to assess whether the sleep states over time demonstrated a fractal nature. Fractal dimension of the raw sleep state waveform as well as a zero-order-hold transformed counterpart were estimated using three methods: Katz, Sevcik, and Lee. Statistical analyses were conducted using correlation, multivariate linear and logistic regression, autocorrelation, power spectrum analysis, and receiver-operating characteristic curve.

Results

Both untransformed and transformed sleep state waveforms exhibited self-similarity. FD of the transformed waveform was significantly associated with a higher apnea–hypopnea index irrespective of the measure of FD. A high proportion of the transition from state 0–2 was significantly associated with a higher fractal dimension and a higher risk of moderate/severe apnea.

Conclusion

In this study, it was demonstrated that the fractal nature of the sleep state waveform is affected in obstructive sleep apnea.

Zusammenfassung

Fragestellung

Schlaf stellt eine komplexes Zusammenspiel biologischer Vorgänge dar. In der vorliegenden Studie wird die Dynamik der Veränderungen von Schlafphasen im Hinblick auf fraktale Eigenschaften und Auswirkungen solcher Veränderungen bei obstruktiver Schlafapnoe untersucht.

Patienten und Methoden

Daten von über Nacht durchgeführten Polysomnographien von 25 Probanden aus einer öffentlich zugänglichen Datenbank wurden daraufhin untersucht, ob die Schlafphasen über die Zeit fraktale Eigenschaften aufwiesen. Die fraktale Dimension (FD) der Rohdaten zur Wellenform der Schlafphasen sowie ein Gegenstück mit Zero-order-hold-Transformation wurden anhand der 3 Methoden nach Katz, Sevcik und Lee ermittelt. Statistische Analysen erfolgten mittels Korrelation, multivariater linerarer und logistischer Regression, Autokorrelation, Power-Spektrum-Analyse und ROC („receiver-operating characteristic curve“).

Ergebnisse

Sowohl die nichttransformierten als auch die transformierten Wellenformen von Schlafphasen wiesen Selbstähnlichkeit auf. Die FD der transformierten Wellenformen war unabhängig von einer FD-Messung signifikant mit einem höheren Apnoe-Hypopnoe-Index assoziiert. Ein hoher Anteil der Übergänge von Stadium 0 zu Stadium 2 war signifikant mit einer höheren FD und einem höheren Risiko einer mittelgradigen/schweren Apnoe verbunden.

Fazit

In der vorliegenden Studie wurde gezeigt, dass die fraktalen Eigenschaften der Wellenform von Schlafphasen bei obstruktiver Schlafapnoe beeinflusst werden.

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Conflict of interest

The corresponding author states that there are no conflicts of interest.

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Authors and Affiliations

  1. Lata Medical Research Foundation, 9/1, Vasantnagar, 440022, Nagpur, India

    T. Thakre MD, M. Mamtani, S. Ujaoney & H. Kulkarni MD

  2. School of Medicine, University of Missouri, Kansas City, MO, USA

    T. Thakre MD

  3. Texas Biomedical Research Institute, 7620 NW Loop 410, 78227, San Antonio, TX, USA

    H. Kulkarni MD

Authors
  1. T. Thakre MD
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  2. M. Mamtani
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  3. S. Ujaoney
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  4. H. Kulkarni MD
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Correspondence to H. Kulkarni MD.

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Thakre, T., Mamtani, M., Ujaoney, S. et al. Fractal dimension of the sleep state waveform in obstructive sleep apnea. Somnologie 15, 249–256 (2011). https://doi.org/10.1007/s11818-011-0537-6

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  • DOI: https://doi.org/10.1007/s11818-011-0537-6

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