Abstract Introduction The incidence of nightmares and dreams during clinically indicated polysomnography (PSG) is rarely reported. We sought to (1) describe the incidence of nightmares and dreams during PSG, (2) PSG characteristics of nightmares and dreams, and (3) identify clinical correlates. Methods Ninety-three patients undergoing an initial clinically indicated PSG had a post-PSG and initial intake questionnaire reviewed. Questionnaires included Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI) and Nightmare Disorder Index (NDI), as well as a structured post-PSG dreams and nightmares questionnaire. Dreams were self-reported, and a nightmare was differentiated from a bad dream if the former caused a patient-reported awakening. Results Overall, 87.1% were Active Duty and 89.2% reported the presence or absence of dreams. In total, 50.5% (47) reported no dreams, 22.6% (21) reported a dream, 2.2% (2) a bad dream, and 14% (13) a nightmare with 12/13 reporting details of their nightmare. The mean total NDI differed significantly between groups (6 ± 5 vs. 7 ± 6 vs. 12 ± 0 vs. 11 ± 5, respectively) (p=0.029). The groups were not significantly different based on sex, age, BMI, diagnosis of depression, anxiety, PTSD, TBI, chronic pain, being prescribed a sleep aid or psychoactive medication, or their ESS and ISI values. PSG characteristics including REM percentage did not differ significantly between groups. Of those reporting a nightmare 75% (9) reported associated autonomic symptoms and 5 (41.7%) reported a trauma related nightmare (TRN). Of those with a TRN, one was related to combat, one sexual assault, two an accident, and one related to death. Two patients with TRN reported their nightmare was an accurate replay of the trauma, 2 reported a mix of replay/non-replay events, and one did not answer. Conclusion Despite rare reports of nightmare capture in sleep labs, our cohort uniquely demonstrated that at least half of first time PSG patients at a military sleep center experience a dream or nightmare during their PSG. Higher NDI scores may predict who is more likely to suffer from a bad dream or nightmare in the sleep lab. Assessing for the occurrence of dreams or nightmares during PSG is likely indicated. Support (if any)
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