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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.