Multiscale adaptive analysis of circadian rhythms and intradaily variability: Application to actigraphy time series in acute insomnia subjects

• Published in: PloS one Vol. 12; no. 7; p. e0181762
• Main Authors: Fossion, Ruben, Rivera, Ana Leonor, Toledo-Roy, Juan C., Ellis, Jason, Angelova, Maia
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 28.07.2017; Public Library of Science (PLoS)
• Subjects: Actigraphy - methods; Acute Disease; Adolescent; Adult; Adults; Analysis; Biology and Life Sciences; Care and treatment; Circadian rhythm; Circadian Rhythm - physiology; Circadian rhythms; Comparative analysis; Data processing; Decomposition; Female; Fractals; Humans; Insomnia; Male; Medicine and Health Sciences; Methods; Multiscale analysis; People and Places; Physical Sciences; Polysomnography; Power law; Psychobiology; Psychological aspects; Research and Analysis Methods; Sleep; Sleep disorders; Sleep Initiation and Maintenance Disorders - physiopathology; Spectrum analysis; Studies; Time Factors; Time series; Variability; Young Adult; Young adults; Mexico
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0181762

Circadian rhythms become less dominant and less regular with chronic-degenerative disease, such that to accurately assess these pathological conditions it is important to quantify not only periodic characteristics but also more irregular aspects of the corresponding time series. Novel data-adaptive techniques, such as singular spectrum analysis (SSA), allow for the decomposition of experimental time series, in a model-free way, into a trend, quasiperiodic components and noise fluctuations. We compared SSA with the traditional techniques of cosinor analysis and intradaily variability using 1-week continuous actigraphy data in young adults with acute insomnia and healthy age-matched controls. The findings suggest a small but significant delay in circadian components in the subjects with acute insomnia, i.e. a larger acrophase, and alterations in the day-to-day variability of acrophase and amplitude. The power of the ultradian components follows a fractal 1/f power law for controls, whereas for those with acute insomnia this power law breaks down because of an increased variability at the 90min time scale, reminiscent of Kleitman's basic rest-activity (BRAC) cycles. This suggests that for healthy sleepers attention and activity can be sustained at whatever time scale required by circumstances, whereas for those with acute insomnia this capacity may be impaired and these individuals need to rest or switch activities in order to stay focused. Traditional methods of circadian rhythm analysis are unable to detect the more subtle effects of day-to-day variability and ultradian rhythm fragmentation at the specific 90min time scale.