If you’re regularly waking up mid-dream it could be an early warning sign of dementia, a study suggests.
Researchers found people who go into REM sleep (the part of the sleep cycle responsible for dreams) later in the night are more prone to or more likely to have dementia.
The researchers believe this could be because REM sleep is essential for producing melatonin, which helps clear out toxic proteins linked to brain damage.
One sign that you’re entering REM (rapid eye movement) sleep late or not getting enough is waking up in the morning in the middle of a dream, scientists say.
This is why people report the phenomena after a night of drinking alcohol, which suppresses REM sleep and pushes it further back in the cycle.
Dr Yue Leng, from UCSF and lead author behind the new study, 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.
Researchers at the University of California – San Francisco (UCSF) found people who took longer to reach REM sleep were more at risk for dementia (stock image)
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, scientists at the China-Japan Friendship Hospital in Beijing tracked the sleeping patterns of 128 volunteers, with an average age of 70.
Half had Alzheimer’s, and about one-third had mild cognitive impairment, a frequent precursor to Alzheimer’s. The rest had normal cognition.
Researchers tracked their brainwave activity, eye movement, heartrate and breathing during a night spent in the clinic.
They then divided the participants into early and delayed REM sleep.
The early group typically reached REM less than 98 minutes after falling asleep, while the late group took more than 193 minutes.
The above graph shows rates of Alzheimer’s per 100,000 people, both age-standardized and all ages. Age-standardization is a method used to adjust for differences in age distribution between populations or over time, while non-age-standardized is the raw rate calculated across all age groups in the population without any adjustment
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.’