Tuesday, November 19, 2013

Sleep

Kelly and I often read in the evening. Ah the benefits of not having a TV! But I probably should be more accurate – weekdays (when I get to work out in the afternoon) Kelly reads and I typically fall asleep. Then, some time later when Kelly is ready, we curl in and the next thing I know it is morning.

One of the benefits I feel pretty profoundly from working out is that I sleep very well. In fact, come Sunday night I can tell that I am not getting to sleep as easily as I do week-nights - my body is telling me I am ready to hit the gym again!

I know I need my 8 hours sleep. Going 4 or 5 days without 8 hours and I just don’t feel as perky in the morning. And I know that I don’t function as well. One would think there has to be a pretty significant need for any activity that we spend about a third of our lives doing.

I have read about sleep in the past – the many theories about how it works to keep us healthy: It seems to be pretty critical for health and well-being. Whilst I am sure there are many aspects of our need for sleep I think recent research on how the brain purges waste products perhaps offers the most salient reason we need sleep.

Research on mice has shown that there is a system in the brain that is similar in function to the lymphatic system in the rest of our body. The lymphatic system removes wastes from the body so that they can be destroyed in the liver. Most of us have had a doctor feel our lymph nodes to see if they are full. Typically full lymph nodes mean our lymphatic system is being called on to purge something from our body - like the byproducts of an infection.

The system in the brain, dubbed the glymphatic system, acts as a trash removal system for the fluids that circulate in the brain. This trash transport occurs in the spaces between the brains cells – these non-neuronal cells are called glia. Hence calling the system they make up the glymphatic system.

This glia system is responsible for removing waste products generated by the neuronal cells in our brain. The team that did this research had a hunch that the brain could not both process sensory information and clean itself at the same time. So they decided to test how the activity of the glymphatic system changed during sleep.

They tested mice and found that the channels that make up the glymphatic system – the pipe-work if you will – expanded significantly when the mice were asleep. This change is important: The flow of cerebral fluid when awake was found to be only 5% of the flow when the mice were sleeping. This translates to a 20 times greater flow when asleep. As in wow.

OK – great bit of information – we all need more sleep. We all pretty much know that. But, other than feeling “out of it”, like our brain is just not operating the way it ought to when we don’t get enough sleep – are there any other issues here?

Interestingly, chronic and complete insomnia ultimately lead to death in mice and humans. Lack of sleep results in poor decision making, impaired learning, increased risk of migraines and epileptic attacks.

What I found pretty darned compelling was that one of the specific metabolites in the brain - β-amyloid - is cleared twice as fast from the brains of the mice when sleeping as when awake. Why is this important to me? Because β-amyloid has been implicated in the progression of Alzheimer’s disease. Or, as one of the articles I read pointed out: “Many neurological diseases - from Alzheimer’s disease to stroke and dementia - are associated with sleep disturbances. The study suggests that lack of sleep could have a causal role, by allowing the byproducts to build up and cause brain damage.”

The articles also discuss the possibility that the buildup of metabolic byproducts could be what makes us sleepy - that our brain is telling us we need to sleep so it can do its housekeeping.

As people age many find they don’t need as much sleep. I’m not sure this is a good thing, given the potential link between lack of sleep and some very serious health hazards. Unfortunately, if one does not do much during the day it is a lot harder to get a good nights sleep. I fear that the sedentary lifestyle that is all too prevalent in America causes more than just obesity, heart disease and diabetes.

My bottom line - exercise assures me a good nights sleep. If this helps to keep my brain functioning as I get older - helps me to avoid Alzheimer’s, dementia and stokes - this is a huge benefit to exercise!

The information for this posting came from three articles in the 18 October edition of Science. I strongly recommend this magazine if you want to keep up with developments in the scientific community.

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