Memory loss in elderly people linked to poor quality sleep

As the middle frontal lobe of the brain deteriorates as people get older, it undermines the ability to enter deep sleep, which is crucial for storing memory. Photo/FILE 

By CHRISTABEL LIGAMI

In Summary

• Poor quality sleep in adults causes memory to stay stuck in the hippocampus and not reach the prefrontal cortex, a part of the brain where long-term memory is stored. This results in forgetfulness and difficulty remembering names.
• As the middle frontal lobe of the brain deteriorates as people get older, it undermines the ability to enter deep sleep, which is crucial for storing memory.

Poor quality sleep among the elderly can cause significant memory loss and brain deterioration, a recent study has shown.

Researchers at the University of California in Berkeley found that during sleep, important brain waves are produced which play a vital role in storing memories.

The brain waves transfer memories from a part of the brain called the hippocampus to the prefrontal cortex, a part of the brain where long-term memory is stored.

Poor quality sleep in adults causes memory to stay stuck in the hippocampus and not reach the prefrontal cortex. This results in forgetfulness and difficulty remembering names.

The researchers assessed the memory of 18 young adults in their 20s and 15 older adults in their 70s after sleeping.

The participants were tested on 120 word sets before they went to bed, and an electroencephalographic (EEG) machine monitored their brain activity while they were asleep.

When they woke up they were tested once again on the word pairs, however this time they took the tests while undergoing functional and structural Magnetic Resonance Imaging (MRI) scans.

The quality of deep sleep among the older adults was 75 per cent lower than the younger ones, and as a result their memory was 55 per cent worse the next day.

The researchers found evidence to suggest that deterioration of the frontal lobe is linked to impaired wave activity.

“What we have discovered is a dysfunctional pathway that helps explain the relationship between brain deterioration, sleep disruption and memory loss as we get older, and with that, a potentially new treatment avenue,” said UC Berkeley sleep researcher Matthew Walker, an associate professor of psychology and neuroscience.

“When we are young, we have deep sleep that helps the brain store and retain new facts and information. But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night.”

He explains that in non rapid-eye movement sleep, the brain produces waves from the middle frontal lobe. As this part of the brain deteriorates — which commonly happens among the elderly — it undermines the ability to enter deep sleep, which is crucial for storing memories.

“Most people don’t move when they’re asleep, and we developed a way to use the data we collected as a marker for whether a person was asleep or awake,” said Prof Walker. “This data let us assess sleep efficiency, which is a measure of how much time in bed is spent asleep.”

On average, those with preclinical disease were in bed as long as other participants, but they spent less time asleep. They also napped more often.

The findings are very promising for the future and development of treatments for memory loss among the elderly.

The researchers are planning on conducting a further study to see if there is a way of enhancing sleep among the elderly, which would allow proper storage of memory and reduce overall forgetfulness.

Another study by the Washington University School of Medicine has also suggested that an early sign of dementia (a loss of brain function that occurs with certain diseases) could be disrupted sleep patterns.

According to the researchers, disrupted sleep seems to be linked to the accumulation of amyloid plaques inside the brains of people not having problems with memory.

Amyloid plaques are a characteristic marker for early stage Alzheimer’s disease.

The study indicated that sleep is disrupted in people who are likely to have early dementia, but do not yet have the memory loss or other cognitive problems characteristic of full-blown disease.

They concluded that people who spent less than 85 per cent of their time in bed actually asleep were more prone to having the amyloid plaques than those who spent more than 85 per cent of their time actually asleep.