Assessment of Multifractal-Multiscale Properties of Heart Rate Variability in Sleep Disorders.

Cardiovascular signals exhibit self-similar characteristics that can be altered by sleep disorders. This study evaluates the multifractal-multiscale structure of heart rate variability (HRV) components in some sleep disorders, such as sleep apnea and REM sleep behavior disorder (RBD), to describe possible alterations in cardiovascular control. For this purpose, the HRV signal was decomposed into intrinsic mode functions (IMFs) using the complete ensemble empirical mode decomposition with adaptive noise method. Then, the IMFs were analyzed by the multiscale-multifractal detrended fluctuation analysis. In addition, a multifractal index was also calculated to describe the multifractality at each scale. Results showed an increase in the scaling coefficients, α(q, τ), in IMF1 and a decrease in IMF4 apnea patients, which may be associated with respiratory events. In RBD, α(q, τ) decreased in IMF1-IMF3 at short scales, suggesting abnormal autonomic modulation. These findings reveal alterations in the fractal properties of HRV, which reflect autonomic dysfunction in sleep related to sleep disorders.Clinical relevance- The analysis of self-similarity using a multifractal-multiscale approach, provides additional information to the classic indices of heart rate variability that could contribute to the early detection of cardiovascular impairment.