Sleep Evaluation of autonomic nervous system in sleep apnea patients using pupillometry under occlusal stress: a pilot study Annalisa Monaco 1 , Ruggero Cattaneo 1 , Luca Mesin 2 , Edoardo Fiorucci 3 , Davide Pietropaoli 1,4 1 Department of Life, Health and Environmental Sciences, Dental Unit, University of L’Aquila, Italy, 2 Department of Electronics and Telecommunications, Politecnico di Torino, Italy, 3 Dipartimento di Ingegneria Industriale e dell’Informazione e di Economia, University of L’Aquila, Italy, 4 Department of Medicine, Case Western Reserve University, Cleveland, OH, USA Aims: Recently, it has been proposed that obstructive sleep apnea syndrome (OSAS) is characterized by an imbalance in autonomic nervous tone. Pupil size has been considered a valid test for studying the autonomic nervous system (ANS). Pupillometry is a simple and non-invasive tool to assess the size and dynamics of the pupil. The purpose of this study was to evaluate, by pupillometry, the hypothesis that subjects with OSAS present ANS dysregulation. Methods: The study group included 10 males aged between 40 and 50 years with polysomnographic diagnoses of mild OSAS. The control group included 10 males with similar ages with an apnea–hypopnea index (AHI) of less than 5, after polysomnography. Pupillometry was performed by digital infrared pupillometer (25 frame/s). Recordings were processed to measure the area of the pupil frame by frame. The subjects underwent four subsequent recordings: infrared light at rest mandible position (RP); infrared light at forced habitual occlusion (FHO); yellow-green light at RP; and yellow-green light at FHO. According to literature, linear and non-linear information was extracted from the recordings. Results: As expected, the two groups did not differ statistically in age and body mass index (BMI), while there was a significant difference in the AHI. In the within-group comparison of pupil size, there were significant differences between RP and FHO under infrared conditions in the control group. There was a significant difference in the determinism percentage (Det%) in the RP infrared condition between the control and OSAS groups. Conclusions: The results of the current study confirm ANS dysregulation in OSAS patients and provide a new possible strategy for studying this pathology by using pupillometry through linear and non-linear mathematical models. Keywords: Autonomic nervous system, ANS, Obstructive sleep apnea syndrome, OSAS, Pupillometry, ANS dysregulation, Forced habitual occlusion, Rest mandible position Introduction Recently, it has been proposed that patients with obstructive sleep apnea syndrome (OSAS) are char- acterized by an imbalance in autonomic nervous tone. In particular, some authors suggested that sympathetic hypertonus is positively correlated with daytime sleepiness. 1 Sympathetic hypertonus could correspond to impaired reactions to several physiological stimuli, which are dependent on the severity of OSAS. 2 On the other hand, sympathetic hyperactivity would largely be responsible for the heart and metabolic diseases that frequently affect these patients. 3 Some results 4 suggested that autonomic abnormalities suggestive of decreased adrenergic tone are associated with mild obstructive sleep apnea (OSA) and may potentially be secondary to OSA, but may also precede development of OSA. Parasympathetic system dysfunction may play a key role in the dysregulation of the autonomic nervous system (ANS) in OSAS patients. 5 Indeed, Correspondence to: D Pietropaoli, Department of Life, Health and Environmental Sciences, San Salvatore Hospital, University of L’Aquila, Building Delta 6 – Unit of Dentistry, Via Vetoio, 67100 L’Aquila, Italy. Email: davide.pietropaoli@graduate.univaq.it ß W. S. Maney & Son Ltd 2014 DOI 10.1179/0886963413Z.00000000022 CRANIOH: The Journal of Craniomandibular & Sleep Practice 2014 VOL. 32 NO.2 139