Researchers have explored the relationship between the build-up of an Alzheimer’s hallmark protein – amyloid – and the stage in the sleep cycle important for memory formation. The research was published in the journal Nature Neuroscience on 1 June 2015.
The researchers, based in the United States, wanted to explore the link between the amyloid protein and sleep patterns. They were particularly interested in a stage of the sleep cycle called non-rapid eye movement (NREM), thought to play a role in memory consolidation.
The study involved 26 healthy people with an average age of 75. The volunteers did not have any memory or thinking difficulties but a brain scanned showed that they all had clumps of amyloid in the brain. The protein can build up in the brain normally with age, but does not always cause symptoms of dementia. The researchers focused on memory retrieval, and asked volunteers to perform a word pair test before and after 8 hours of sleep. They carried out the memory test in a functional MRI scanner – a sophisticated tool for assessing brain activity. This provides a window into the function of the part of the brain involved in memory formation.
The team found that amyloid build-up in the frontal regions of the brain was associated with disruptions to the NREM stage of the sleep cycle. They also found that those with disrupted NREM sleep had more difficulties with the memory retrieval task. The researchers suggested memory problems in old age could be in part linked to disrupted sleep associated with amyloid build-up.
Dr Eric Karran, Director of Research at Alzheimer’s Research UK, said:
“A bad night’s sleep can play havoc with memory and thinking skills in all of us in the short term. This small study suggests that the build-up of abnormal proteins in the brain as we age is associated with problems in sleep cycles, which could lead to difficulties with memory retrieval. It is always difficult to tease apart cause and consequence and as this study was carried out in healthy older people, rather than in those with dementia, it is not possible to conclude that disrupted sleep causes memory difficulties in the condition. This study is a snap-shot and so it would be interesting to expand the research to look at changes in memory over time. With 225,000 people a year in the UK developing dementia, it is critical that we invest in research to find ways to tackle the condition head-on.”