“Glymphatic” Neurodegeneration: Is Sleep the Missing Key?

Robust evidence suggests that the glymphatic system plays a key role in preserving brain health. Indeed, its activity in maintaining homeostasis by clearing neurotoxic proteins such as beta-amyloid from the human brain is essential. Sleep represents the factor that mainly influences this system, since it is selectively active during the night, in particular during non-rapid eye movement (NREM) sleep. This is true, since the sleep head position, in particular the supine position for its relationship to the status of opening/closing of the jugular veins, appears to be determinant for the development of future neurodegeneration. Growing evidence from human and animal models highlights the neurobiological link between sleep, glymphatic dysfunction and neurodegeneration. On the other hand, several modifiable factors have been recently identified modulating (improve/reduce) glymphatic system activity, such as Omega-3 polyunsaturated fatty acids, stress, hypertension, physical activity, alcohol, gender and genetic predisposition, in particular variants of aquaporin-4 (AQP4). From this viewpoint, our ambition is to discuss how the glymphatic system works in the brain, what factors mainly impact on this activity and its strict relation with the neurodegeneration. Future directions might include the analysis of factors modulating glymphatic system activity and a personalized glymphatic profile, “glymphatom”, as a natural target for preventive neurodegenerative treatment.