Recently, dementia researchers have taken a keen interest in sleep.

There are several reasons. Most of all, there is no cure for dementia, and there is a growing body of evidence that sleep is deeply related to dementia.

"That is because it has been confirmed that amyloid protein increases when there is a problem with sleep, and the risk of dementia increases," said Professor Jung Ki-young of the Department of Neurology at Seoul National University Hospital in his book “The Power of Sleep,” published in the second half of this year.

Professor Jung added that studies also show that treating sleep apnea, which reduces sleep quality, significantly reduces amyloid protein, so managing sleep well can reduce the risk of dementia.

According to experts, sleep acts as a brain scavenger, as toxic proteins that build up in the brain are flushed out during sleep, and Alzheimer's disease, the most common form of dementia, is particularly associated with amyloid proteins.

"The metabolites produced by our brain's activity are released and dissolved through sleep," Professor Jung said. "When toxic beta-amyloid proteins build up in the brain, hyperphosphorylated tau proteins aggregate in nerve cells and form neurofibrillary knots, which eventually degenerate nerve cells and cause dementia."

This suggests that improving sleep health may reduce the risk of dementia.

"In a 25-year follow-up study of more than 100,000 people in the United Kingdom, researchers found that people who slept less than six hours in their 50s and 60s were 20 to 30 percent more likely to develop dementia than those who slept seven hours," Jung said. "People who slept more than seven hours had a similarly high incidence of dementia as those who slept less."

While sleep duration is important, sleep quality can also greatly impact dementia. The glymphatic system is responsible for clearing metabolites from the brain, which is why studies have shown that metabolites are cleared at twice the rate during sleep, especially deep sleep, than during wakefulness.

"If you have poor sleep or a sleep disorder, you can expect to see a decrease in the excretion of amyloid protein and an increase in its accumulation in the brain, which increases the risk of dementia," Professor Jung said, emphasizing maintaining healthy sleep quantity. Quality is important for healthy living in later life.