Spinal cord injuries (SCI) are associated with altered cardiovascular autonomic control. Sleep is characterized by modifications of autonomic control across sleep stages; however, no data are available on the effects of SCI on CAC during sleep. The aim of our study was to assess cariac autonomic modulation during sleep in SCI patients.
Overnight polysomnographic recordings were obtained in 27 patients with cervical (Cerv) and thoracic (Thor) SCI and in healthy subjects (Controls). ECG and respiration were extracted from PSG, divided into sleep stages (W, N2, N3 and REM) for assessment of CAC, using symbolic analysis and Corrected Conditional Entropy. SA identifies three main indices, 0V%, index of sympathetic modulation, and 2LV% and 2UV%, markers of vagal modulation. CCE evaluates the complexity of heart period time series.
Symbolic analysis revealed a reduction of 0V% in N2 and N3 compared to W and REM and an increase of 2LV% and 2UV% in N2 and N3 compared to W and REM in SCI patients, independent of the level of the lesion, and similar to Controls. Corrected Conditional Entropy was higher in N2 and N3 compared to W and REM in all three groups.
In SCI patients, cardiac autonomic control changed across sleep stages, with a reduction of sympathetic and an increase of parasympathetic modulation during NREM compared to W and REM and a parallel increase of complexity during NREM, similar to Controls. Cardiac autonomic dynamics during sleep are maintained in SCI, independent of the level of the lesion.
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