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Waking up mid-dream could be an early warning sign of dementia, a study suggests.
People who go into rapid eye movement (REM) sleep - the part of the sleep cycle responsible for dreams and storing memories - later in the night are more prone to or more likely to have dementia.
The researchers believe this could be because REM sleep is crucial for the production of melatonin. , which aids in eliminating harmful proteins associated with brain damage.
According to researchers, one indication that you might be experiencing delayed REM sleep or insufficient amounts of it is frequently waking up during a dream.
That's why following a night of alcohol consumption alcohol you're less likely to sleep soundly, as alcohol suppresses REM sleep.
Dr Yue Leng, associate professor in the Department of Psychiatry and Behavioral Sciences at UCSF, said: 'The delay in REM sleep disrupts the brain's ability to consolidate memories by interfering with the process that contributes to learning and memory.
'If it is insufficient or delayed, it may increase the stress hormone cortisol. This can impair the brain's hippocampus, a critical structure for memory consolidation.'
The study comes as dementia kills more than 288,000 Americans every year and affects about 7million.
REM follows three phases of non-REM sleep, each deeper than the last.
The four phases take 90 minutes or more to complete, depending on age, and a person may cycle through them four or five times in a typical night.
Older people take longer to reach REM.
In the new study , researchers from the China-Japan Friendship Hospital have Beijing monitored the sleep cycles of 128 participants whose average age was 70 years.
Approximately half were diagnosed with Alzheimer’s disease, and around one-third exhibited signs of mild cognitive impairment, which often precedes Alzheimer’s. The remaining participants showed typical cognitive function.
Scientists monitored their brainwave patterns, ocular movements, heart rate, and respiration throughout the night at the facility.
They subsequently split the participants into groups based on early and delayed REM sleep stages.
The early group typically reached REM less than 98 minutes after falling asleep, while the late group took more than 193 minutes.
Those with Alzheimer’s were more likely to have delayed REM sleep, 16 percent more amyloid and 29 percent more tau than those with early REM sleep.
These are toxic proteins that clump together in the brain to form plaques in nerve cells, disrupting normal communication and killing them off.
Previous research on mice has suggested melatonin can boost REM sleep and decreases tau and amyloid accumulation.
Other drugs that treat insomnia by blocking a chemical that suppresses REM sleep have also been shown to decrease tau and amyloid.
The scientists suggested that people who are concerned about their Alzheimer's risk should 'practice healthy sleep habits' that help shift from light to REM sleep.
Dr Dantao Peng, an expert in neurology at the China-Japan Friendship Hospital and study senior author, added: 'This includes treating conditions like sleep apnea and avoiding heavy drinking, since both can interfere with a healthy sleep cycle.
'Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor, if they are worried about Alzheimer's.'
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