Sleep disruption associated with the build-up of hallmark Alzheimer’s proteins
18 July 2017
Sleep disordered breathing is a condition characterised by periods of not breathing enough or even at all during sleep. The most common form is obstructive sleep apnea (OSA), in which periods of disordered breathing occur when a person’s upper airway closes. OSA has previously been linked with dementia, and in these new studies, research teams from Wheaton College, USA, have explored the associations between sleep disordered breathing and hallmark Alzheimer’s proteins in the brain, reporting their findings at the Alzheimer’s Association International Conference 2017.
In the first study, the researchers looked at the accumulation of amyloid protein in the brains of 516 healthy older people who did not have memory problems. They found that people with self-reported sleep disordered breathing had higher levels of amyloid in the brain as measured by brain scans. Over time, they saw that amyloid accumulated at a faster rate in those with sleep disordered breathing compared with those without.
The research team in the second study looked at 798 people with mild memory problems, known as mild cognitive impairment (MCI). Not everyone with MCI goes on to develop dementia, however a person with MCI is at an increased risk of developing Alzheimer’s or another form of dementia. Using brain scans, the researchers tracked amyloid levels in the brain over time, looking to see whether having OSA had an effect on levels of the the protein. People who self-reported having OSA showed a faster increase in the build-up of amyloid in their brain compared to those who did not have OSA.
In the third study, the team looked at the same groups as in the other two studies, as well as 325 people with Alzheimer’s disease. They followed these groups for an average of 2.5 years, testing brain and spinal fluid (cerebrospinal fluid; CSF), as well as carrying out amyloid brain scans. The team found that people with self-reported OSA in the healthy aged or MCI groups showed faster changes in CSF amyloid and tau, indicating greater build-up in the brain compared with people without OSA. This was supported by amyloid brain scans, showing faster accumulation of amyloid in the people with OSA in the healthy aged and MCI groups.
Dr Carol Routledge, Director of Research at Alzheimer’s Research UK, said:
“Conditions such as sleep disordered breathing can get in the way of a restful night’s sleep, and may have wider reaching health impacts. Researchers are beginning to explore the emerging links between sleep disruption and dementia to unravel the factors at play. This research reveals a relationship between obstructive sleep apnea and the build-up of hallmark Alzheimer’s proteins in the brains of people with no memory problems and those with mild memory complaints. We know that Alzheimer’s proteins can start to build-up over a decade before symptoms appear so it is often difficult to tease apart cause and effect in the relationship between sleep problems and dementia. Understanding how sleep disorders could affect our risk of dementia is of great importance, especially if managing these conditions could help to reduce the number of people developing dementia.”