Poor quality sleep linked with ‘biological fingerprint’ of Alzheimer’s in healthy older people

05 July 2017

Researchers in the US have found a link between poor sleep and a ‘biological fingerprint’ indicative of hallmark Alzheimer’s protein, amyloid building up in the brains of healthy aged people. The findings are published today (5 July) in Neurology.

The researchers were interested in exploring the link between sleep quality and Alzheimer’s disease in a group of healthy older people. They studied a group of people who are at an increased risk of developing Alzheimer’s, due to having at least one parent who had developed the disease. The participants were part of the Wisconsin Registry for Alzheimer’s Prevention (WRAP), an observational study that explores how lifestyle factors could alter the risk of developing Alzheimer’s.

The researchers used data from people in the WRAP study, such as measures of sleep quality and tests of cerebrospinal fluid (CSF), the fluid that bathes the brain and spinal cord and is collected by a lumbar puncture. By analysing the CSF and looking at the levels of a number of different proteins, known as biomarkers, the team could gain insight into changes in the brain, such as the build up of the hallmark Alzheimer’s proteins, amyloid and tau, as well as proteins indicating damage to nerve cells. These changes in biomarkers in CSF are thought to indicate the early stages of Alzheimer’s.

The researchers analysed data from 101 people in the WRAP study who had information about both sleep quality and CSF biomarkers. The participants had an average age of 64, and none of the participants had any problems with memory and thinking. The researchers found that self-reported reduced sleep quality and daytime sleepiness were associated with evidence in CSF of increased build up of amyloid and tau in the brain. However, the researchers did not find an association between sleep disorders, such as obstructive sleep apnea, and evidence of increased amyloid and tau in the brain. Loss of connections between nerve cells is thought to happen early on in the Alzheimer’s disease process, however the team did not find a link between loss of nerve cell connections and poor sleep quality.

Dr Carol Routledge, Director of Research at Alzheimer’s Research UK, said:

“We all recognise that a bad night’s sleep can have consequences on brain activity in the short term, but a growing body of evidence points to a link between long term sleep quality and the development of diseases like Alzheimer’s. This new research found a link between self-reported sleep quality and indications of Alzheimer’s in healthy older people, but we do not know whether these people will go on to develop the symptoms of dementia. This study does not tell us about cause and effect in this relationship, and questions remain as to whether poor sleep quality increases dementia risk or if disrupted sleep is a very early sign of changes in the brain in dementia. Future studies will need to explore this association in order to understand the molecular processes that could be behind this link. With over half a million people living with Alzheimer’s in the UK and that number on the rise, it is vital that we invest in research to unpick the causes of Alzheimer’s and find ways to tackle it.”