Multisensory dysfunction across sleep disorders: A systematic review of 31 human modalities.

Sleep disorders are increasingly understood as systems-level conditions in which the brain and body reweight sensory evidence from the external world and internal milieu. We systematically reviewed human evidence for sensory and multisensory dysfunction across sleep disorders and experimental sleep loss. Searches identified 25,777 records; after removal of 7235 duplicates, 18,542 records were screened, 4452 full records were assessed for eligibility, and 377 studies met inclusion criteria. Evidence was organised across 31 sensory modalities in seven domains: olfaction, gustation, vision, audition, somatosensation/nociception, vestibular-proprioceptive function, and interoception/autonomic function, with higher-order perceptual outcomes analysed separately. Using a prespecified conservative criterion requiring a non-null direction of effect with at least moderate certainty, 23 of 31 modalities were altered in at least one sleep disorder or experimental sleep-loss category (74.2%). The evidence clustered in specific disorder-domain pairs. Moderate-certainty signals identified clinically meaningful hyposmia in isolated rapid eye movement sleep behaviour disorder and obstructive sleep apnoea, heightened pain sensitivity in chronic insomnia, altered chronoception after experimental sleep loss, and obstructive sleep apnoea-associated hearing-threshold impairment. Central auditory-processing, visual, gustatory, and vestibular-proprioceptive findings were more heterogeneous or lower certainty. Across disorders, the emerging map is consistent with state-dependent disturbances in sensory gain, gating, salience, and interoceptive control. These findings position sensory profiling as a clinically tractable strategy for phenotyping and for prospective evaluation of risk and treatment response in selected sleep disorders. Longitudinal and interventional studies should now test whether sensory measures predict disease course, sleep stability, and clinical outcomes, and whether targeted sensory or interoceptive modulation can improve sleep-related symptoms.