Sleep Disorders in Neurodegenerative Diseases: Pathological Correlations and Underlying Mechanisms

Neurodegenerative diseases (NDDs), including Alzheimer's disease (AD), Parkinson's disease (PD), multiple system atrophy (MSA), amyotrophic lateral sclerosis (ALS), and others, represent an escalating public health burden in aging populations. NDDs are characterized by progressive neuronal loss and misfolded protein aggregation. Despite distinct clinical heterogeneity, these diseases universally present with debilitating non-motor symptoms, among which sleep-wake disorders are highly prevalent. Once considered secondary to neuronal damage, growing evidence now highlights a bidirectional interplay: sleep disruption is not only a consequence of neurodegeneration but also exacerbates its progression. This review synthesizes this complex interplay, outlining sleep phenotypes across major NDDs, dissecting key underlying mechanisms (impaired protein homeostasis, glymphatic dysfunction, chronic neuroinflammation, sleep-regulatory nucleus vulnerability, and circadian dysregulation), and summarizing current pharmacotherapeutic and non-pharmacological interventions. Attenuating sleep disorders may therefore provide symptomatic relief and disease‑modifying effects for NDDs.