Swimming in cold water could protect the brain from degenerative diseases such as dementia, researchers from the University of Cambridge have found.
For the first time ever, a 'cold shock' protein has been found in the blood of regular winter swimmers at London's Parliament Hill pool.
This protein has been shown to slow the progression of dementia and can even repair some of the damage done to mice.
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Professor Giovana Malucci, who heads the UK Dementia Research Institute's Center at the University of Cambridge, says this discovery could lead researchers to new drug-based therapies that could prevent the onset of dementia.
This research - although very promising - is still in its early stages, but it deals primarily with the ability to hibernate, which all mammals possess, and which is activated by exposure to cold.
There are already more than a million people with dementia in the UK, and the total is expected to double by 2050.
Researchers are looking for new ways to treat this condition, as current options have only limited effectiveness.
Bears and hedgehogs
Doctors have known for decades that cooling people can - under certain circumstances - protect their brains.
People with head injuries and those who need heart surgery are often cooled down during surgery, just like babies.
What is still not well understood is why the cold has this protective effect.
The connection to dementia lies in the destruction and formation of synapses - the connection between cells in the brain.
In the early stages of Alzheimer's and other neurodegenerative diseases, these connections in the brain are lost.
This leads to a whole cascade of symptoms associated with dementia - such as memory loss, confusion and mood swings - as well as, over time, the death of entire brain cells.
What intrigued Professor Maluča was the fact that brain connections are lost when hibernating animals, such as bears, hedgehogs and bats, fall into hibernation.
About 20-30 percent of their synapses die as their bodies lay down precious reserves for the winter.
But when they wake up in the spring, those bonds are miraculously restored again.
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Why common cold it can be dangerousa
Cold has a strong effect on the human body.
The shock of entering icy water causes a dramatic spike in heart rate and blood pressure, which can lead to heart attacks and strokes in people with chronic illnesses.
It also causes a gag reflex and rapid breathing, which can lead to suffocation if water is inhaled.
The more time someone spends in the water, the slower their reactions are.
People can become confused and clumsy, and find it difficult to extricate themselves from the water.
Dr. Heather Macy from the Extreme Environments Laboratory at the University of Portsmouth, says that some key things must not be forgotten.
- Before entering the cold water, make sure you are fit and healthy. If you are not sure, consult your doctor
- Swim with others who are used to cold water and know the local dangers
- Get out as soon as you start to feel cold
- Find shelter, remove wet clothing and replace with as many layers of warm, dry clothing as you can, such as a wool hat and gloves
- Move around, do light exercises if you can and don't worry about shivering - it will help you warm up
But Dr. Macy says you should never take a hot shower or a hot bath.
Changes in your blood pressure as you rewarm can lead to fainting and the risk of physical injury.
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"Cold Shock" Chemicals
In 2015, a dementia team from Cambridge discovered "cold shock chemicals" that trigger this entire process.
They cooled normal mice and mice with Alzheimer's and prion (neuro-degenerative) disease to the point where they reached hypothermia, meaning their body temperature dropped below 35 degrees Celsius.
When rewarmed, they found that only normal mice could regenerate their own synapses; mice with Alzheimer's and prion disease could not.
At the same time, they found that levels of a "cold shock" protein called RBM3 jumped in the normal mice, but not in the others.
This suggested that RBM3 may be the key to forming new connections.
They proved the link in a separate experiment that showed that brain cell death in Alzheimer's and prion diseases could be prevented by artificially boosting RBM3 protein levels in mice.
It was a huge breakthrough in dementia research, and their findings were published in the scientific journal Nature.
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Winter swimmers
Professor Malucci believes that a drug that increases the production of the RBM3 protein could slow down - perhaps even partially stop - the progression of some neuro-degenerative diseases in humans.
RBM3 has not been found in human blood, so the obvious next step was to investigate whether this protein is even present in the human population.
In an interview with BBC Radio 4's Today programme, Professor Malucci explained that she would like to test the role of the RBM3 protein in humans - but that ethical guidelines make it very difficult to get permission to subject people to hypothermia.
And that's where Martin Pate comes in, one of a small group of people who swim all winter long in the unheated outdoor pool on Hempstead Heath in London.
He and other swimmers voluntarily expose themselves to hypothermia every day, he wrote to her in an email, and therefore would be ideal subjects for the study.
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Professor Maluči agreed and during the winter of 2016, 2017 and 2018, her team tested winter swimmers for this protein.
The researchers used members of a Tai Chi club who practiced by the pool but never entered the water as a control group.
The Cambridge team found that a significant number of swimmers had significantly elevated levels of the RBM3 protein.
They all reached hypothermia, with body temperatures that could drop as low as 34 degrees Celsius.
No member of the Tai Chi group showed an increase in RBM3 protein levels or experienced these low body temperatures.
Can the cold slow down dementia?
The Cambridge work on winter swimmers has been shared in online lectures but has not yet been published in scientific journals.
A number of other researchers have also found similarly high levels of RBM3 protein in babies and heart disease or stroke patients who have reached hypothermia.
What these findings show, says Professor Malucci, is that - just like hibernating mammals - humans produce a "cold shock" protein.
But the risks of freezing greatly outweigh the potential benefits, so immersion in ice water is certainly not a potential therapy for dementia, she says.
The challenge now, she says, is to find a drug that stimulates the production of this protein in humans and - more importantly - to prove that it really helps delay dementia.
Dementia is primarily a disease of older people, so even a relatively short delay in the progression of the disease can have enormous benefits for individuals and the wider population.
Professor Malucci says: "If you could manage to slow down the progress of dementia even for a few years in the entire population, it would have enormous positive consequences, both economically and health-wise."
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