More dream sleep 'could help avoid dementia'
24th August 2017 – People who dream less frequently during sleep may be more likely to develop dementia, a study suggests.
Researchers found that each percentage reduction in REM sleep is associated with approximately a 9% increase in the risk of developing dementia.
Rapid eye movement sleep
REM – or rapid eye movement – sleep is the stage when dreaming occurs. It is characterised by an increase in brain activity as well as higher body temperature, quicker pulse and faster breathing. It is a period of sleep that improves brain function and creates long-term memories.
The first REM stage occurs about an hour to 90 minutes into sleep and then recurs several times during the night, with longer periods usually later into our sleep.
During sleep, we cycle between REM and non-REM sleep.
It is increasingly thought that sleep disturbance is a risk factor for dementia. To explore this, US and Australian scientists examined sleep data from 321 people over the age of 60 who were part of a study examining sleep and heart health.
Over an average of 12 years, 32 of the participants were diagnosed with some type of dementia, 24 of them with Alzheimer's.
The study, published in the journal Neurology, found that those who developed dementia spent an average of 17% of their sleep time in REM sleep, compared to 20% for those who did not develop dementia.
The researchers say the results were similar even after excluding other risk factors for dementia, such as heart disease, depression and medication use.
No associations were found between non-REM stages of sleep and dementia risk.
More research is needed to explore how the dreaming stage of sleep can affect the chances of developing dementia, the researchers say.
Commenting on the findings, Dr Alison Evans of Alzheimer’s Research UK says in a statement: "Sleep disturbance is a common symptom for people living with Alzheimer's disease and a number of other forms of dementia. This small study adds to evidence of sleep changes preceding the onset of memory and thinking changes, and suggests that levels of REM sleep may be particularly relevant to the risk of future dementia symptoms.
"We know that brain changes in diseases like Alzheimer’s can begin in the brain over a decade before symptoms start to show, and it is impossible to tell from this study whether disturbed REM sleep could be causing increased dementia risk or whether it’s an early consequence of disease processes already underway in the brain. It is also possible that REM sleep may be disturbed as a result of stress, a factor that has previously been linked to an increased risk of dementia."
Dr James Pickett, head of research at the Alzheimer’s Society comments in a statement: "Researchers found that only a small number of people on the study developed dementia and so we can't draw any firm conclusions from this work alone. However, it does show the value of recording people's sleep patterns in-depth to gain a more accurate idea of what aspect of sleep could contribute to risk, and that it is more complex than simply counting the hours we spend in bed.
"Over the next few years we should hope to see some answers to the novel questions about the role that sleep plays in dementia risk, including whether sleep disturbance is a contributing factor to dementia risk or is caused by the early stages of the condition.
"Studies can also start to test if correcting sleep abnormalities can reverse any increase in risk."