Sleep disorders and acute nocturnal delirium in the elderly: A comorbidity not to be overlooked

• Sleep disorders can be at the root of confusional behaviours seen in delirium.
• Clinicians should consider the risk of overlooking sleep comorbidities in delirium.
• Sleep disorders should be considered in the overall evaluation of nocturnal delirium.
• Nocturnal polysomnography should be performed in cases of suspected OSA.
• Diagnosis and treatment of disrupted sleep should be obtained when appropriate.

Delirium is a disturbance of consciousness and cognition that results in a confusional state. It tends to fluctuate in intensity and is often observed in older patients. Sleep is a window of vulnerability for the occurrence of delirium and sleep disorders can play a role in its appearance. In particular, delirious episodes have been associated with obstructive sleep apnoea syndrome, which is reported to be frequent in the elderly.Hereby, we present a case-report documenting the sudden onset of a confusional state triggered by obstructive sleep apnoea-induced arousal, together with a review of the literature on the topic. We emphasise that, among the many pathogenic factors implicated in delirium, it is worth considering the possible link between nocturnal delirium and the occurrence of impaired arousals. Indeed, the complex confusional manifestations of delirium could be due, in part, to persistence of dysfunctional sleep activity resulting in an inability to sustain full arousal during behavioural wakefulness.Arousals can be triggered by sleep disturbances or other medical conditions. Clinicians should be aware that older patients may present disordered sleep patterns, and make investigation of sleep patterns and disorders potentially affecting sleep continuity a key part of their clinical workup, especially in the presence of cognitive comorbidities.Correct diagnosis and optimal treatment of sleep disorders and disrupted sleep can have a significant impact in the elderly, improving sleep quality and reducing the occurrence of abnormal sleep-related behaviours.