Alzheimer's disease as a systems-level timing disorder: Circadian disruption of glial immunometabolism, brain clearance, and therapeutic responsiveness

Feb 18, 2026Neurobiology of sleep and circadian rhythms

Alzheimer's disease as a timing problem: disrupted daily rhythms in brain support cells, waste removal, and treatment response

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Abstract

Alzheimer's disease (AD) may be reframed as a systems-level timing disorder disrupting the brain's temporal organization.

Circadian clocks in healthy brains coordinate essential processes such as sleep-wake behavior and immune function.
In AD, there is a deterioration of temporal coordination, leading to sleep fragmentation and instability in daily activity patterns.
Disruptions in circadian rhythms can create inappropriate immune and metabolic states that impair protein clearance.
Extracellular vesicles may change from waste export mediators to facilitators of disease spread in the context of circadian failure.
Circadian dysfunction impacts therapeutic delivery and biomarker interpretation by affecting blood-brain barrier transport and brain fluid dynamics.

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Alzheimer's disease (AD) is traditionally conceptualized as a disorder of protein aggregation and neurodegeneration, yet growing evidence indicates that fundamental temporal organization of brain physiology is also disrupted. In the healthy brain, circadian clocks coordinate sleep-wake behavior, glial immunometabolism, astrocytic aquaporin-4 polarity, and glymphatic-lymphatic clearance, aligning immune readiness and proteostasis with daily activity-rest cycles. In AD, this temporal coordination progressively deteriorates, manifesting as sleep fragmentation, instability of rest-activity rhythms, vulnerability of central clock structures, and loss of circadian gating of glial and clearance pathways. These disruptions create phase-inappropriate immune and metabolic states, impair protein clearance, and alter the fate of extracellular vesicles, which may shift from mediators of waste export to facilitators of proteopathic spread. Importantly, circadian failure also constrains therapeutic delivery and biomarker interpretation by modulating blood-brain barrier transport, brain fluid dynamics, and brain-to-blood signal export. We propose that AD can be reframed as a systems-level timing disorder, in which loss of temporal coherence integrates molecular pathology, glial dysfunction, clearance failure, therapeutic inefficacy, and biomarker variability. This framework highlights chrono-pharmacology, chrono-neurotherapeutics, and circadian-informed biomarkers as essential components of precision strategies for AD prevention and treatment.