Sleep Problems? It May Indicate An Early Warning Sign Of Alzheimer's

We all feel better after a good night’s sleep, but research is starting to uncover even more important implications of poor sleep.  Disturbed sleep has been linked in animals and humans with the development of degeneration within the brain which leads to diseases such as Alzheimer’s, and Parkinson’s. 

How was the link first discovered?

It all came about when scientists studying mice realized that the levels of a protein (amyloid-beta) which is linked with Alzheimer’s, were lower during sleep compared with in the waking hours.  This connection has also now also been found in humans.

Normal age-related decline in brain function and in Alzheimer’s in particular, is associated with accumulation of solid deposits (‘plaques’) of this protein in the brain. The protein measured in the studies however, was a soluble form, dissolved in the fluid around the brain.

It had been thought that build-up of the plaques was what caused the degeneration in the brain, but a new theory is that they protect the brain from the effects of the soluble protein, which is toxic.  So it may be that during sleep these defences against the disease are more active or more effective.  

Link with different types of sleep disturbance

The effects of sleep deficit on brain function have been linked with more than one type of sleep disturbance.  They include being unable to sleep (insomnia), as well as sleep apnoea.  This is where breathing during sleep is very shallow and stops every now and again.  Typically this leads to daytime fatigue, which has been linked to the degenerative changes seen in the brain.

An early or a late warning

Some research seems to show that sleep disturbance may predispose to degenerative brain disorder many decades before the onset of the disease. But a large study of over 14,000 people aged over 50 years found that people with sleep problems were more likely to receive a diagnosis of Alzheimer’s sooner - within two to four years of their sleep problems.

Cause or effect?

And while lack of sleep is thought to play a part in causing degenerative brain disease, it also appears that the diseases themselves predispose to disturbed sleep, producing a vicious cycle.

Other warning signs

It is said that the subjects of our dreams can indicate what is going on in our lives and this appears to be true for people in the early stages of Parkinson’s disease.  It is common for the dreams of these people to be full of animals and aggressive (as opposed to friendly) behavior.

Wakefulness And Parkinson’s Disease

The study previously mentioned also found a link between sleep deficit and other brain disorders including Parkinson’s disease. This disorder is characterised by destruction of the brain cells which produce a chemical messenger called dopamine.  In addition to other important functions, this substance is important in making the distinction between being asleep or awake.  Drugs like amphetamine, are known to stimulate dopamine activity, increasing wakefulness.

Sleep and our body clock

Although we live and work to a 24-hour day, our own internal body clock has its own cycle, known as circadian rhythm.  Studies have shown that before developing Alzheimer’s, the internal body clock of mice becomes disordered and the part of their brain which controls it is also where they lose brain cells in Alzheimer’s disease.  Genetic variations have been found which may predispose to disordering of circadian rhythm, and possibly also to degenerative brain diseases.

What is the significance of this research?

Although these studies seem to indicate a link between disrupted sleep and degenerative brain disorders, whether it is a causal link ie lack of sleep causes diseases like Alzheimer’s, has yet to be proven.  This could only be done by treating the sleep disturbance, such as apnoea, in one group of people at risk of developing Alzheimer’s while leaving a comparable group untreated.  But withholding a treatment would be considered unethical, so this type of trial is unlikely to happen.

So can nothing be done?

Although many of the studies so far have been in animals, David Holtzman feels that it will be shown to also apply in humans.  The good news is that he is confident that the link between sleep disruption and degenerative brain disease can be reversed:

Alpar Lazar, a researcher in sleep and neurodegenerative diseases at the University of Cambridge, agrees as he has found that sleep disturbance worsens, the closer people are to their diagnosis of Parkinson’s Disease. Even long before that diagnosis their sleep disturbance is much worsethan in people who do not develop the disease.  He said:

Is there any proof this will work?

It’s early days, but there are some seeds of hope from people treated for sleep apnoea. When they are successfully treated so that they get a good night’s sleep and are not drowsy the next day they are more cheerful and memory and brain function have been shown to be improved.  The hope is that treating sleep disorders might not only prevent or delay onset of brain diseases, but also slow down normal age-related cognitive decline.

As people are now surviving to much greater ages, this could be important in preserving quality of life into those advanced years.