Étude de la sensibilité baroréceptive en sommeil et à l’éveil dans l’insomnie primaire chronique

Insomnia, one of the most common sleep complaint in the general population, is characterised firstly by a difficulty initiating or maintaining sleep and/or early awakenings or non-restorative sleep. Insomnia is defined as primary when not principally due to another medical or psychiatric condition or other sleep disorder, whereas a minimum of 6 months duration is required to define chronic insomnia.  Some authors have hypothesized that insomnia is associated with a state of hyperarousal characterized by increased sympathetic activity during sleep and wakefulness.  The arterial baroreflex is an important mechanism providing continuous short term regulation of heart rate and blood pressure (BP) by means of the autonomic nervous system influences over the pacemaker and the peripheral circulation.  Baroreflex sensitivity (BRS) is the baroreflex’s capacity to react and control BP changes by adjusting the heart rate.  BRS is known to be heightened during the night compared to daytime. Also, it seems that the baroreflex could be involved in the physiological day-to-night BP fall.  Previous data from our laboratory demonstrated in subjects with chronic primary insomnia, higher night-time systolic BP and a significant attenuation of the physiologic day-to-night systolic BP fall compared to good sleepers.  Besides, the baroreflex has been shown to be altered early in several cardiovascular diseases and to precede hypertension.  Subjects with insomnia have been shown to have a higher likelihood to develop daytime hypertension.  All of these findings point in the direction of altered BP regulatory mechanisms in insomnia.  Furthermore, a reduction of BRS could be implicated in states where higher sympathetic autonomic activity is observed.  We hypothesised that the baroreflex could be one of the BP control mechanisms which are altered in insomnia and could be involved in the heightened sympathetic activity observed in insomnia.  To our knowledge, the baroreflex has never been investigated previously in insomnia.  The primary goal of this study was to investigate non-invasively BRS during wakefulness and sleep in 11 subjects with chronic primary insomnia compared to 11 good sleepers.  Baroreflex was investigated spontaneously by the sequence method and by the calculation of the alpha coefficient obtained by cross spectral analysis of RR interval and systolic BP.  Simultaneously, RR interval variability components were also compared during wakefulness and sleep between the two groups. No significant differences were found for indices of BRS between insomniacs and good sleepers during wakefulness and sleep.  However, slightly lower values of BRS during wakefulness and sleep were noted in insomniacs with poor sleep (sleep efficiency (SE) <85%) versus those with good sleep (SE≥ 85%) at the experimental night.  As a secondary finding, no differences were found between the insomniacs and the good sleepers for any of the RR variability components considered (RR interval, PNN50, LF and HF in their normalized units).  Indeed, insomniacs like good sleepers exhibited normal variation of autonomic activity during sleep as depicted by the RR variability components. Our preliminary results suggest that baroreflex mechanisms are preserved in subjects with a subjective complaint of chronic primary insomnia. Nevertheless, certain impairment may occur in insomniacs as a function of objective measures of poor sleep.

Keyphrases: Baroreflex, Insomnia, Autonomic nervous system, Sleep