Just one night of disrupted sleep in healthy adults causes an increase in amyloid beta, a brain protein associated with Alzheimer’s disease.
The study, by the Washington University School of Medicine in the US, also found a link between a week of disrupted sleep and an increase in another brain protein, tau, which has been linked to brain damage in Alzheimer’s and other neurological diseases.
The brains of people with Alzheimer’s have build ups of amyloid beta and tau protein, which cause brain tissue to die. Currently there is no effective therapy to prevent or slow down the condition.
The researchers studied 17 healthy adults between the ages of 35 and 65 with no sleep problems or cognitive impairments. Each participant wore an activity monitor for up to two weeks that measured how much time they spent asleep at night.
After five nights of wearing the monitor, each participant came to the School of Medicine to spend a night in a specially designed sleep room, wearing electrodes on the scalp to monitor brain waves.
Half the participants were randomly assigned to have their sleep disrupted during the night. Every time their brain signals settled into the slow-wave pattern characteristic of REM sleep, the researchers sent a series of beeps through the headphones until they entered shallower sleep.
The next morning they reported feeling tired and unrefreshed, even though they had slept just as long as usual and usually did not recall being woken during the night.
Participants then underwent a spinal tap so the researchers could measure the levels of amyloid beta and tau in the fluid surrounding the brain and spinal cord.
They found a 10 percent increase in amyloid beta levels after a single night of interrupted sleep, but no corresponding increase in tau levels. However, participants whose activity monitors showed they had slept poorly at home for the week before the spinal tap showed increased levels of tau.
The study’s senior author, David Holtzman, said: ‘We showed that poor sleep is associated with higher levels of two Alzheimer’s-associated proteins. We think that perhaps chronic poor sleep during middle age may increase the risk of Alzheimer’s later in life.’
Why we sleep and what happens to our brains during sleep remains a medical enigma and this American study opens up another intriguing possibility. Sleep deprivation may be linked to an increase in brain proteins that are linked with the brain damage found in Alzheimer’s disease. Both of these proteins have been implicated in the development of Alzheimer’s disease. It is important to point out though that the researchers are keen not to imply that a few nights poor sleep increases the risk of dementia in the future – there is no evidence for this. Instead, they conclude that chronic sleep deprivation is not good for our health, which is a well known fact. Neither are chronically elevated levels of amyloid protein in the brain. This is further evidence that a good nights sleep may be better for us than we think.