Wash your hands before coming to the table, your mother used to tell you. She was afraid you would contaminate your food with the bacteria stuck on your hands from playing outside. Hygiene is very important, also for the brain. But too much of it can cause problems.
Better hygiene is one of the pillars of our growing life expectancy, together with advanced medical care. But it is not only good news about being more hygienic. Hospitals are supposedly one of the most sterilised environments in the world, but have immense problems lately getting rid of a nasty, resistent bacterium called MSRA which through hospital-acquired infections make people sick within the hospital where they came to be cured.
Not only do we damage our environment with effective, but toxic cleaning products, but we also kill more than we should. We need bacteria and cannot survive without their help. The micro-organisms living in our digestive tract, also known as gut flora, are an extreme example. If our gut flora is healthy, we are healthy. If it is weakened, we become ill.
Researchers from Lund University in Sweden recently delved into bacteria living on our skin. They found these bacteria in general to be beneficial for their host. The most common bacteria on human skin turns out to secrete a protein which protects against the production of nasty molecules that damage cells. Oxidative stress, as this is called, is thought to contribute to skin diseases. The bacterium living on our skin – with the impressive name of Propionibacterium acnes – needs the protective protein to survive and in the process helps us too.
Does hygiene have a link with Alzheimer disease? Scientists from University of Cambridge and University of Glasgow in the UK, University of Utah in the US, and McMaster University in Canada think so. Inflammation seems to play an important role in Alzheimer disease, like it does in autoimmune diseases. It has been found exposure to micro-organisms may improve our immune system which protects against autoimmunity. Prevalence of autoimmune diseases varies between populations. They appear to occur less frequent in less urbanised countries with more pathogens and a lower degree of sanitation.
Could the same be true for Alzheimer disease, the scientists theorised. They checked the presence of Alzheimer’s in different countries and found that it occurs more in countries with a greater degree of sanitation and less pathogens. They concluded that there seems to be a link between hygiene and Alzheimer disease risk. People living in sanitised environments may be at greater Alzheimer’s risk.
Although exposure to pathogens strengthens our immune system, within our brain hygiene is of utmost importance. Garbage collectors play a central role in keeping the brain healthy. There is a constant turnover of brain cells and debris of dead neurons needs to be removed quickly to make sure surrounding cells can continue to function properly. Special cells, called microglia, are responsible for getting rid of this debris.
Spanish researchers discovered these microglia don’t seem to function properly anymore during neurodegenerative diseases. They seem to go blind, so to speak, and seem to be unable to find dead neurons and destroy them. This causes a piling up of garbage, which kills nearby neurons too. Damage spreads through the brain, which is the course of neurodegenerative diseases. Further research will have to show whether making microglia function well again will stop neurodegeneration in its track.
The lymphatic system, which is part of the immune system, helps our body get rid of unwanted intruders and waste. Recently, it was discovered the brain also contains a similar system. Researchers of the University of Rochester in the US who discovered this system, named it glymphatic system, in reference to glial cells in the brain that are organising the work.
A timely removal of waste is essential for keeping the brain healthy. Accumulation of toxic proteins and other debris will cause disruptions in the brain’s functioning. This may result in neurodegenerative diseases. The glymphatic system is controlled by astrocytes, a star-shaped glial cell which is very numerous in the brain and which has a number of very important functions.
The astrocytes in the glymphatic system use cerebrospinal fluid. This fluid circulates through interconnected holes in the brain, among other things to create a cushion to protect the brain from impacts. Astrocytes form a kind of plumbing system, hooking up to blood vessels, to pump cerebrospinal fluid through brain tissue. Thus waste is flushed away from the spaces between brain cells. The cerebrospinal fluid takes the garbage with it when it enters the blood stream after having circulated.
One of the outcomes of the research is that blows to the head may damage the waste removal system. That is why traumatic brain injury early in life is a risk factor for early development of dementia.
Another finding is that this glymphatic system is most active while we sleep. Since it becomes more difficult to get good quality sleep as we age, that may be a reason why functioning of the system is declining. And as a result of the accumulation of waste, cognitive decline may occur.
When we don’t get enough sleep, the glymphatic system doesn’t have sufficient time to do its housework. We do really need our beauty sleep to get our brain cleaned!
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