[Lifestyle] Does sleep clear more toxins from the brain than when we’re awake? Latest research casts doubt on this theory

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There’s no doubt sleep is good for the brain. It allows different parts to regenerate and helps memories stabilise. When we don’t get enough sleep, this can increase stress levels and exacerbate mental health issues. Evidence also supports the notion that the brain gets rid of more toxic waste when we’re asleep than when we’re awake. This process is believed to be crucial in getting rid of potentially harmful things such as amyloid, a protein whose build-up in the brain is linked to Alzheimer’s disease.However, a recent study in mice has come to the opposite conclusion. Its authors suggest that in mice, brain clearance is actually lower during sleep – and that previous findings could also be re-interpreted in this way. The brain’s cleaning system Since the brain is an active tissue – with many metabolic and cellular processes happening at any moment – it produces a lot of waste. This waste is removed by our glymphatic system.Cerebrospinal fluid is a crucial part of the glymphatic system. This fluid surrounds the brain, acting as a liquid cushion that protects it from damage and provides it nourishment, so the brain can function normally. During the waste removal process, our cerebrospinal fluid helps transfer old and dirty brain fluid – full of toxins, metabolites and proteins – to outside the brain, and welcomes in new fluid.The waste that has been removed then ends up in the lymphatic system (a part of your immune system), where it’s ultimately eliminated from your body. The glymphatic system was only discovered in the last decade or so. It was first observed in mice, using dyes injected into their brains to study the movement of fluids there. The existence of the glymphatic system has since been confirmed in humans with the use of MRI scans and contrast dyes. Based on the results of animal experiments, scientists concluded the glymphatic system is more active at night, during sleep or when under anaesthesia, than during the day. Other studies have shown this waste removal activity may also vary depending on different conditions – such as sleep position, the type of anaesthetic used, and whether or not the subject’s circadian rhythm was interrupted.The recent study used male mice to examine how the movement of brain fluid differed when animals were awake, asleep and anaesthetised. The researchers injected dyes into the animals’ brains to track the flow of fluid through the glymphatic system. In particular, they examined whether an increase in dye indicated a decrease in fluid movement away from an area, rather than an increase in movement to the area as previous studies had suggested. The former would mean lower clearance via the glymphatic system – and hence less waste being removed.

https://indianexpress.com/article/lifestyle/health/does-sleep-clear-more-toxins-from-the-brain-than-when-were-awake-research-9369125/