The sleep-deprived blood-brain barrier: Does the Brain's gatekeeper adapt or merely fail slowly?

Chronic insufficient sleep is highly prevalent and is linked to an elevated risk of adverse health outcomes. Animal studies show that chronic sleep restriction, inducing a cumulative sleep debt, promotes blood-brain barrier (BBB) dysfunction, neuroinflammation, and can insidiously lead to neuropathology. Available studies primarily show diurnal or time-of-day variation in BBB permeability rather than direct manipulation of sleep state. Therefore, our fundamental understanding of BBB dynamics during the sleep-wake cycle remains limited. Investigating dynamic changes in the BBB induced by prolonged wakefulness is critical for understanding the heightened vulnerability of the brain to neurodegenerative diseases. In this review, we first discuss the potential role of sleep to modulate BBB dynamics. We then examine the known mechanisms driving BBB changes during sleep loss across different experimental paradigms and critically discuss the bidirectional interplay between sleep and the BBB, emphasizing how disruption of one system affects the other. This narrative-based review challenges the prevailing view of the BBB as a static, whole-brain barrier, proposing instead that it is a dynamic and adaptive interface whose regulation is tightly coupled to neuronal demands across the sleep-wake cycle.