## 2 Materials and Methods
In accordance with AASM guidelines [26], the sleep analyses were performed in 30 s epochs and were directed towards a series of specific parameters: sleep onset latency from lights off; REM sleep latency from the sleep onset; wakefulness after sleep onset; total sleep time (TST); sleep period from sleep onset to lights on; sleep efficiency; percentage of time spent in each sleep stage; awakenings; awakenings per hour; respiratory disturbance index; apnea/hypopnea index; and periodic limb movement index. Patients of more than 18 years of age who received a diagnosis of NT1 after the L-PSG, according to the ICSD-3 criteria [22], were included and assigned to the N group. Patients with normal neurophysiological results, ruling out nocturnal sleep disorders and excluding EDS, were assigned to the control group. All subjects were provided with the \"Information sheet on participation in the study\", signed the privacy policy, and gave written informed consent to be enrolled in the study. The study was approved by the Ethics Committee of the Area Vasta Emilia Centro of the Emilia-Romagna Region (CE-AVEC) with the number 449-2019-OSS-AUSLBO. All patients were examined by the same operator expert in orofacial pain following the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) [43], which is considered the gold standard for TMD diagnoses. The protocol includes a clinical examination using reliable and well-operationalized diagnostic criteria (AXIS I) to evaluate physical signs and symptoms, such as TMJ movement disorders, TMJ sounds, TMJ pain on palpation, and masticatory muscle pain on palpation. An evaluation of the psychological status of the subject and pain-related disability (Axis II) was also performed. The patients were asked to fill out the TMD pain screener [44], the Graded Chronic Pain Scale (GCPS) [45] to describe pain intensity and pain-related disability, the Jaw Functional Limitation Scale (JFLS) [46] to evaluate functional status of the masticatory system, the Patient Health Questionnaire-9 (PHQ-9) [47] to assess psychological distress due to depression, the Generalized Anxiety Disorder-7 (GAD-7) assessment [48], the physical symptoms questionnaire (PHQ-15) [49], and the Oral Behaviors Checklist (OBC) [50] to investigate the frequency of oral para-functional habits. Pain sensitivity was investigated by the measurement of pressure pain thresholds (PPTs) [51], which can be defined as the minimum pressure inducing pain and represent a reliable parameter to investigate pain sensitization [52,53]. The PPTs were evaluated by one calibrated examiner with a Fischer algometer (Pain Diagnostics and Thermography, Great Neck, NY, USA), a force gauge fitted with a rubber disc that had a surface area 1 cm\({}^{2}\), which when pressed against the surface of a person's body, measures pressure in kg/cm\({}^{2}\), with a range of up to 10 kg and 100 gr divisions. The device consists of a metal rod with a male thread on one end, onto which the rubber disc is screwed. Pressure exerted on the rod moves the indicator in a clockwise direction. Pressing the zeroing knob returns the indicator to zero after each measurement; the force value obtained is held until the zeroing knob is pressed, allowing readings even after the algometer is removed from the subject's body. The examiner trained for one week, learning to reach an increasing pressure rate of 100 gr/sec continuously, as suggested by [PERSON] [52] and [PERSON] [54], who demonstrated that a higher pressure-increasing rate may lead to overestimation of PPTs. At the start of the examination, the subjects were familiarized with the measurement procedure and equipment by means of a demonstration on the right forearm and were instructed to keep their teeth slightly apart, in order to avoid contraction of the jaw-closing muscles during stimulation. During the examination, subjects were seated in a standardized position.