Characterisation of sleep disturbances in postural orthostatic tachycardia syndrome: A polysomnography-based study

Background and Aim: Postural orthostatic tachycardia syndrome (PoTS) has been frequently associated with sleep disturbances but objective sleep data are lacking. In addition, although regional autonomic denervation has been described, less is known about autonomic nervous activity overnight in these patients. Patients/Methods: A full polysomnography and heart rate variability were performed on 37 patients diagnosed with PoTS In addition, a multiple sleep latency test (MSLT) was conducted on a subgroup of patients with excessive daytime sleepiness. Results: The polysomnographic data did not show major pathological findings except the percentage spent in rapid eye movement (REM) sleep which was slightly reduced at 18.4%. The MSLT did not confirm excessive daytime sleepiness as median mean sleep latency was 14.4 min (11.8-17.5). When comparing patients with and without subjective daytime sleepiness, it was found that the latter had a reduced parasympathetic activation at night as expressed by the average high frequency [6936.5 ms2 (6028.2-8675.5) vs. 4689.5 (3922.7-7685.2) p < 0.05]. Conclusion: Patients with PoTS do not exhibit polysomnographic findings consistent with relevant sleep pathologies nor objective daytime sleepiness. Subjective daytime sleepiness is associated with enhanced activation of the parasympathetic nervous system.