Sleep does NOT clear brain of toxins – but exercise does, finds study

It’s always a relief to crawl into bed at the end of a long day.

But the exact reason why people need sleep is still a mystery, according to new research.

It has long been thought that the brain uses sleep to flush out toxins and remove harmful molecules.

However, a new study suggests the opposite may be true – and experts say being active may be more beneficial for ‘cleaning’ the brain.

A team from the UK Dementia Research Institute at Imperial College London used a fluorescent dye to study the brains of mice, tracking how quickly the dye moved from one part of the brain to another before it was finally cleared.

They found that fluid clearance and movement were significantly reduced during sleep and under anesthesia.

Analysis showed that clearance of the dye was reduced by about 30 percent in sleeping mice and by 50 percent in anesthetized mice, compared to mice kept awake.

Although the findings have yet to be confirmed in humans, it casts doubt on the long-standing belief that sleep removes toxins through the glymphatic system, a mechanism that flushes waste from the brain.

Previous research has suggested that sleep is important for preventing dementia because toxic proteins are removed from the brain during this time.

Co-lead author of the study Nick Franks, professor of biophysics and anesthetics at Imperial College London, said: ‘The field has been so focused on the idea of ​​clearance as one of the main reasons we sleep, and we were of course very surprised to see the opposite in our results.’

The researchers also said that the size of molecules may affect how quickly certain toxins move through the brain, and that some compounds are removed through different systems.

‘As yet we don’t know what it is about these conditions that slow the removal of molecules from the brain,’ added Professor Franks.

‘The next step in our investigation will be to try to understand why this is happening.’

Study co-leader Prof. Bill Wisden, interim center director of the UKDRI, said: ‘There are many theories about why we sleep, and while we have shown that clearing out toxins may not be the main reason, it cannot be disputed. that sleep is an important reason. important.

‘Disturbed sleep is a common symptom in people with dementia. However, we still don’t know whether this is a consequence or a driving factor in the progression of the disease.

‘It may well be that a good night’s sleep helps reduce the risk of dementia for reasons other than clearing out toxins.

‘The other side of our research is that we have shown that brain clearance is very efficient during the waking state.

“In general, being awake, active and exercising can cleanse the brain of toxins more efficiently.”

The findings have been published in the journal Nature Neuroscience.