How All-Nighters Literally Clog the Brain
Written By Rathusha Nimalan
Edited By Gesi Huang
If you’ve ever pulled an all-nighter, whether it be to cram for an exam, catch up on job applications, or simply because you – oddly enough – believed it would be fun, you are likely familiar with the foggy, sluggish aftereffects the next morning, when just one blink threatens to topple you into oblivion. When your friends ask why you cannot stop yawning, you make your normal excuses – but what if I told you that the problem goes far beyond “being tired and sleep-deprived?” That, in reality, your brain’s plumbing system is being clogged? Recent neuroscience research has revealed that the brain has its own network to drain waste, separate from the lymphatic system.
The human body’s lymphatic system plays an essential role in draining excess fluid and clearing cellular waste from metabolism occurring throughout the human body. The brain, however, is enclosed by the blood-brain barrier and lacks lymphatic capillaries that allow for fluid movement and waste clearance into the lymphatic system [2]. So, how is waste removed from the brain?
In 2012, at the University of Rochester’s Medical Center, neuroscientist Maiken Nedergaard and her lab discovered that the central nervous system of the human body uses cerebrospinal fluid (CSF) to wash away waste in brain tissue. Her team named this system the “glymphatic system,” as it was analogous to the lymphatic system. Nedergaard’s discovery proved that the brain has its own clearance pathway that depends on CSF, blood vessels, and astrocytes – a type of glial cell in the brain – that work to keep the neural space clean [1].
Produced in the brain’s ventricles, CSF flows throughout the brain and functions in carrying nutrients, clearing waste, and distributing important brain chemicals. After circulation, it either drains into the body’s meningeal lymphatic system lining the spinal cord and brain, or loops back into the brain through the glymphatic system.
Photos by SCHVETS production. Curated by Leticia De Almeida Smolka (lds234@cornell.edu)
Astrocytes, as mentioned above, are a type of supportive glial cell in the nervous system. They line the spaces around blood vessels, allowing CSF to mix with the interstitial fluid between brain cells to remove toxins. Toxins that may accumulate in the brain include the metabolic waste products of lactate and cellular debris, as well as harmful proteins such as amyloid-β and tau, which are tied to neurodegenerative diseases like Alzheimer’s.
Scientists still do not know the specific pathways traversed by interstitial fluid in the brain, nor the exact location where the glymphatic system connects to the lymphatic system. However, Nedergaard’s research strongly suggests the presence of a separate, specialized network of clearance pathways in the brain that are distinct from the rest of the body. The ability to remove waste improves brain efficiency and function, including the coordination of long-range processes through hormone activity, immune surveillance, distribution of nutrients, and bulk fluid signaling. Without such a system, harmful proteins and metabolites would accumulate, impairing synaptic function and contributing to neurodegenerative diseases.
Where do all-nighters come into play? In fact, researchers have found that sleep is correlated with glymphatic activity. Studies on rodents show that CSF influx and clearance are dramatically enhanced during sleep as compared to wakefulness (Xie et al., 2013; Hablitz et al., 2020). The glymphatic system is synchronized to the circadian cycle; only during sleep is the rapid clearance of metabolic waste initiated. Once the body is awake, CSF is diverted to the mandibular lymph nodes, reducing glymphatic transport in the brain. Additionally, hormones like norepinephrine, which are typically elevated while awake, also suppress glymphatic flow.
It is only to be expected that pulling all-nighters leads to brain fog, reduced memory consolidation, and a buildup of neurological waste. Your brain is stewing in its own waste! Take this as your sign to hit that lights-out switch the next time you are tempted to stay up – your body will thank you for it.
Rathusha Nimalan ‘28 is in the College of Arts and Sciences. She can be reached at rn349@cornell.edu.
