If you wake up regularly, this can be an early warning signal of dementia, a study suggests.
Researchers discovered that people who sleep in REM (the part of the sleep cycle responsible for dreams) are later in the night more susceptible to or more likely to have dementia.
The researchers believe that this can be because REM sleep is essential for producing melatonin, which helps to clean up toxic proteins that are linked to brain damage.
A sign that you let brake (fast eye movement) sleep or not get 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 into the cycle.
Dr. Yue Leng, from UCSF and the main author behind the new study, said: 'The delay in REM sleep disturbs the ability of the brain to consolidate memories by disturbing the process that contributes to learning and memory.
'If it is insufficient or delayed, this can increase the stress hormone cortisol. This can influence the hippocampus of the brain, a critical structure for memory consolidation. '
The study is because dementia kills more than 288,000 Americans every year and affects about 7 million.
Researchers from the University of California – San Francisco (UCSF) discovered that people who lasted longer to reach REM sleep were more at risk for dementia (stock image)
REM follows three phases of non-brake sleep, each deeper than the previous one.
The four phases take 90 minutes or more to complete, depending on the age, and a person can cycle through it four or five times in a typical night.
Older people take longer to reach brake.
In the new study, scientists from the China-Japan Friendship Hospital in Beijing followed the sleep patterns of 128 volunteers, with an average age of 70.
Half had Alzheimer's, and about a third had a mild cognitive disorders, a frequent precursor to Alzheimer's. The rest had normal cognition.
Researchers followed their brain wave activity, eye movement, heartbeat and breathed in the clinic during a night.
They then divided the participants into early and delayed REM sleep.
The early group usually reached brake less than 98 minutes after falling asleep, while the late group lasted more than 193 minutes.
The graph above shows the speeds of Alzheimer's per 100,000 people, both standardized and all ages. Age-standing is a method that is used to fit for differences in age distribution between populations or over time, while non-aged standardized the raw speed is calculated over all age groups in the population without any adjustment
Those with Alzheimer's were more likely to have a delayed brake sleep, 16 percent more amyloid and 29 percent more Tau than that with early brake sleep.
These are toxic proteins that clump together in the brain to form plaques in nerve cells, to disturb and kill normal communication.
Earlier research into mice has suggested that melatonin can stimulate the brake sleep and reduce the accumulation of tau and amyloid.
Other drugs that treat insomnia by blocking a chemical substance that suppresses REM sleep has also been shown to reduce Tau and amyloid.
The scientists suggested that people who are concerned about the risk of their Alzheimer's must practice healthy sleeping habits' who help to switch from light to brake -sleep.
Dr. Dantao Peng, an expert in neurology in the China-Japan Friendship Hospital and studies senior author, added: 'This includes treatment conditions such as sleep apnea and avoiding heavy drinking, because both can disrupt a healthy sleep cycle.
“Patients who take certain antidepressants and sedativa who reduce REM sleep must discuss their concern about their doctor if they are concerned about Alzheimer's.”
