If not dreaming during sleep could be early sign of Alzheimer: Study

People taking longer to enter their ‘dreaming’ phase of sleep could be experiencing an early symptom of Alzheimer’s disease, a neurodegenerative disorder that impairs thought processes and memory, a study has suggested.
 A good night’s sleep is critical as the brain consolidates information learned during the day with previous knowledge before filing it for long-term storage. The rapid eye movement (REM) phase of sleep follows non-REM sleep and is marked by dreaming, along with increased brain activity, heart rate and breathing.

Once asleep, it typically takes around 90 minutes to enter REM sleep, with the cycle repeating four to six times each night. The study, published in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, monitored 128 people during their nighttime sleep and found that those with delayed REM sleep had 16 per cent more amyloid clumps and 29 per cent more tau tangles compared to those with early REM sleep.

Amyloid and tau are proteins in the brain that stick together to form ‘amyloid clumps’ or ‘tau tangles’ in Alzheimer’s patients, damaging brain cells and disrupting their function.

Those with delayed REM sleep also had 39 per cent less of a healthy protein called brain-derived neurotrophic factor (BDNF), levels of which are known to drop in Alzheimer’s disease.

Researchers, including those from the University of California, San Francisco, suggested that those taking significantly longer to enter the REM stage of sleep might be experiencing an early symptom
of the neurodegenerative condition.

The researchers explained that during REM sleep, the brain processes memories, especially those with high emotional content, and stores them for the long term.

“The delay in REM sleep disrupts the brain’s ability to consolidate memories by interfering with the processes that contribute to learning and memory,” said senior author Yue Leng, an associate professor at the University of California, San Francisco.

“If it is insufficient or delayed, it may increase the stress hormone cortisol, which can impair the brain’s hippocampus, a critical structure for memory consolidation,” Leng added.

The team measured brain activity, eye movement, heart rate, and breathing of the participants as they slept at the neurology unit of the China-Japan Friendship Hospital in Beijing. Half of the group
had Alzheimer’s, while about a third had the preceding stage of mild cognitive impairment. The participants were, on average, 70 years old.