Complexity analysis of sleep and alterations with insomnia based on non-invasive techniques

Abstract

For the first time, fractal analysis techniques are implemented to study the correlations present in sleep actigraphy for individuals suffering from acute insomnia with comparisons made against healthy subjects. Analysis was carried out for 21 healthy individuals with no diagnosed sleep disorders and 26 subjects diagnosed with acute insomnia during night-time hours. Detrended fluctuation analysis was applied in order to look for 1/f-fluctuations indicative of high complexity. The aim is to investigate whether complexity analysis can differentiate between people who sleep normally and people who suffer from acute insomnia. We hypothesize that the complexity will be higher in subjects who suffer from acute insomnia owing to increased night-time arousals. This hypothesis, although contrary to much of the literature surrounding complexity in physiology, was found to be correct-for our study. The complexity results for nearly all of the subjects fell within a 1/f-range, indicating the presence of underlying control mechanisms. The subjects with acute insomnia displayed significantly higher correlations, confirmed by significance testingpossibly a result of too much activity in the underlying regulatory systems. Moreover, we found a linear relationship between complexity and variability, both of which increased with the onset of insomnia. Complexity analysis is very promising and could prove to be a useful non-invasive identifier for people who suffer from sleep disorders such as insomnia.

Exponential state transition dynamics in the rest–activity architecture of patients with bipolar disorder

“…The mean ± SD age at onset for BD in this sample was 22.8 ± 9.3 years; patients with comorbid disorders had an earlier age at onset of the disorder [16.1 ± 4.7 versus 24.8 ± 9.8 years for those without comorbid disorders; F = 4.14, p = 0.05], consistent with our previous results . Most of the patients in this sample were taking mood stabilizers; nine were receiving antidepressant treatment, and eight were taking antipsychotics (Table ). Sleep‐aid medications were prescribed for nine of the patients; women were prescribed sleep medications more often than men (χ 2 = 7.59, p < 0.005).…”

Seeking a fingerprint: analysis of point processes in actigraphy recording

“…In particular, actigraphy studies by Sun et al [15] indicated that the scaling exponent of the power law detected in temporal autocorrelation of activity significantly correlates with the severity of Parkinson's disease symptoms. Similarly, universal scaling laws have been found in locomotor activity periods of humans suffering from major depressive disorders [12] and individuals subject to sleep debt [24,25]. The disruption of the characteristic universality classes of such laws has been further addressed by Proekt et al [7] in studies on dynamics of rest and activity fluctuations in light and dark phases of the circadian cycle.…”

“…While such summary measures allow for hypothesis testing using classic statistical methods [14,[21][22][23], large amounts of relevant information are disclosed in those complex data when more advanced tools of quantification (cf. Section 3), like fractal analysis, are applied [11,13,15,17,24,25]. In particular, actigraphy studies by Sun et al [15] indicated that the scaling exponent of the power law detected in temporal autocorrelation of activity significantly correlates with the severity of Parkinson's disease symptoms.…”

“…In order to quantify time-correlations in recorded time series, we have used the DFA method [36,37], frequently applied in analysis of physiological data [25,[38][39][40][41]. The original time series X(t), t = 1, ..., N have been integrated Z(k) = k t=1 [X(t) − X], where X = N t=1 X(t)/N is the data mean and k is an integer number k ∈ {1, ..., N }.…”

Quantification of Irregular Rhythms in Chronobiology: A Time- Series Perspective

“…All time series have a length of N ¼ 20160 data points (corresponding to 7 Â 24 h) (data from the public database of Ref. [43]).…”