[Spectral analysis of the variations in heart rate and cardiac activation on waking up in sleepwalking]

In sleepwalking, a disorder that is characterised by partial waking, the subject experiences an alteration of the microstructure of sleep that can affect autonomous activity during sleep and the waking state.

In order to evaluate any possible upset in the regulation of autonomous functioning in sleepwalkers during sleep and the waking state, we conducted a spectral analysis of their heart rate variability (HRV) during both sleep and the waking state.

Spectral analysis of HRV was conducted in the group of 10 sleepwalkers and 10 normal controls during sleep and during the waking state in both the horizontal and vertical positions. Their pattern of cardiac activation was also analysed during different types of arousal.

There were no differences between the group of sleepwalkers and the control group in the parameters used in the spectral analysis of HRV during sleep and in the horizontal position during the waking state. Sleepwalkers showed a greater shift in the sympathovagal balance in favour of sympathetic activity, as a response to standing. During the 5-minute sequences immediately before the start of pathological arousal in sleepwalkers, the total energy in the spectral analysis of HRV was seen to increase. No differences were found between the patterns of cardiac activation displayed by the groups of patients and normal subjects during several different types of arousal.

Autonomous reactivity was seen to be altered as a response to the orthostatic load in sleepwalkers, which could be the consequence of the instability of these patients' sleep. The increase in the total energy in the spectral analysis of HRV immediately before pathological arousal during NREM 4 sleep in sleepwalkers suggests that autonomous activation precedes cortical arousal.