Late-Onset Disorders of Arousal in an Older Adult Without Family History: A Case Report

Disorders of arousal (DoA) typically present with childhood onset and a positive family history. We report a 66-year-old male with a 2-year history of recurrent nocturnal behaviors characterized by partial awareness, minimal responsiveness, and absent recall unless interacted with. Polysomnography captured events arising from non-rapid eye movement sleep stage 3, characterized by eye opening, vocalization, and gradual reorientation without leaving the bed. Severe obstructive sleep apnea (apnea-hypopnea index, 32.1/hour) was present but temporally dissociated from the behaviors. Other differential diagnoses, including rapid eye movement sleep behavior disorder, epileptic seizures, and delirium, were excluded. The clinical and polysomnographic findings were most consistent with DoA despite the atypical late onset and absence of family history. This case suggests that DoA may occur de novo in older adults and highlights the importance of comprehensive history taking and polysomnographic evaluation.