A good night’s sleep refreshes body and mind, but a poor night’s sleep can do just the opposite.

In fact, one disrupted night’s sleep causes an increase in amyloid beta – a brain protein associated with Alzheimer’s disease.

This is according to research from the Washington University School of Medicine in St. Louis, Radboud University Medical Centre in The Netherlands and Stanford University.

So, what happens when you have a week of restless nights?

According to the study, a week of poor sleep leads to an increase in another brain protein, tau, that has been linked to brain damage in Alzheimer’s disease and other neurological diseases.

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“We showed that poor sleep is associated with higher levels of two Alzheimer’s-associated proteins,” said David M. Holtzman, MD, the Andrew B. and Gretchen P. Jones Professor, Head of the Department of Neurology and the study’s senior author. “We think that perhaps chronic poor sleep during middle age may increase the risk of Alzheimer’s later in life.”

Understanding Alzheimer’s disease

Alzheimer’s disease is characterised by gradual memory loss and cognitive decline.

The brains of people with Alzheimer’s are dotted with plaques of the amyloid beta protein and tangles of tau protein, which together cause brain tissue to atrophy and die.

There are no therapies that have been proven to prevent, slow or reverse the course of the disease.

The sleeping brain

Previous studies by Holtzman and others have shown that poor sleep patterns increase the risk of cognitive problems.

For example, people with sleep apnoea, a condition in which people repeatedly stop breathing at night, are at risk for developing mild cognitive impairment an average of 10 years earlier than people without the sleep disorder.

Mild cognitive impairment is an early warning sign for Alzheimer’s disease.

The sleep study

For the study, 17 healthy adults, ages 35 to 65, wore an activity monitor for up to two weeks that measured how much time they spent sleeping each night.

After five or more successive nights of wearing the monitor, participants spent a night in the School of Medicine specially designed sleep room.

Half the participants were assigned to have their sleep disrupted during the night.

The next morning, the participants who had been beeped out of slow-wave sleep reported feeling tired and unrefreshed, even though they had slept just as long as usual and rarely recalled being awakened during the night. Each 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.

A month later, the process was repeated.

What is slow-wave sleep?

Slow-wave sleep is the deep sleep that people need to wake up feeling rested. It is also the time when neurons rest and the brain clears away the molecular by-products of mental activity that accumulate during the day.

Should you be worried?

Co-first author Yo-El Ju, MD, an assistant professor of neurology, thinks it is unlikely that a single night, or even a week of poor sleep, has much effect on the overall risk of developing Alzheimer’s disease.

She says that amyloid beta and tau levels probably go back down the next time the person has a good night’s sleep.

“The main concern is people who have chronic sleep problems,” Ju said. “I think that may lead to chronically elevated amyloid levels, which animal studies have shown lead to increased risk of amyloid plaques and Alzheimer’s.”

Source: Washington University in St. Louis via www.sciencedaily.com

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