The brain has its own waste disposal system – known as the glymphatic system – that’s thought to be more active when we sleep.

But disrupted sleep might hinder this waste disposal system and slow the clearance of waste products or toxins from the brain. And researchers are proposing a build-up of these toxins due to lost sleep could increase someone’s risk of dementia.

There is still some debate about how this glymphatic system works in humans, with most research so far in mice.

But it raises the possibility that better sleep might boost clearance of these toxins from the human brain and so reduce the risk of dementia.

Here’s what we know so far about this emerging area of research.

Why waste matters

All cells in the body create waste. Outside the brain, the lymphatic system carries this waste from the spaces between cells to the blood via a network of lymphatic vessels.

But the brain has no lymphatic vessels. And until about 12 years ago, how the brain clears its waste was a mystery. That’s when scientists discovered the “glymphatic system” and described how it “flushes out” brain toxins.

Let’s start with cerebrospinal fluid, the fluid that surrounds the brain and spinal cord. This fluid flows in the areas surrounding the brain’s blood vessels. It then enters the spaces between the brain cells, collecting waste, then carries it out of the brain via large draining veins.

Scientists then showed in mice that this glymphatic system was most active – with increased flushing of waste products – during sleep.

One such waste product is amyloid beta (Aβ) protein. Aβ that accumulates in the brain can form clumps called plaques. These, along with tangles of tau protein found in neurons (brain cells), are a hallmark of Alzheimer’s disease, the most common type of dementia.

In humans and mice, studies have shown that levels of Aβ detected in the cerebrospinal fluid increase when awake and then rapidly fall during sleep.

But more recently, another study (in mice) showed pretty much the opposite – suggesting the glymphatic system is more active in the daytime. Researchers are debating what might explain the findings.

So we still have some way to go before we can say exactly how the glymphatic system works – in mice or humans – to clear the brain of toxins that might otherwise increase the risk of dementia.

Does this happen in humans too?

We know sleeping well is good for us, particularly our brain health. We are all aware of the short-term effects of sleep deprivation on our brain’s ability to function, and we know sleep helps improve memory.

In one experiment, a single night of complete sleep deprivation in healthy adults increased the amount of Aβ in the hippocampus, an area of the brain implicated in Alzheimer’s disease. This suggests sleep can influence the clearance of Aβ from the human brain, supporting the idea that the human glymphatic system is more active while we sleep.

This also raises the question of whether good sleep might lead to better clearance of toxins such as Aβ from the brain, and so be a potential target to prevent dementia.

How about sleep apnoea or insomnia?

What is less clear is what long-term disrupted sleep, for instance if someone has a sleep disorder, means for the body’s ability to clear Aβ from the brain.

Sleep apnoea is a common sleep disorder when someone’s breathing stops multiple times as they sleep. This can lead to chronic (long-term) sleep deprivation, and reduced oxygen in the blood. Both may be implicated in the accumulation of toxins in the brain.

Sleep apnoea has also been linked with an increased risk of dementia. And we now know that after people are treated for sleep apnoea more Aβ is cleared from the brain.

Insomnia is when someone has difficulty falling asleep and/or staying asleep. When this happens in the long term, there’s also an increased risk of dementia. However, we don’t know the effect of treating insomnia on toxins associated with dementia.

So again, it’s still too early to say for sure that treating a sleep disorder reduces your risk of dementia because of reduced levels of toxins in the brain.

So where does this leave us?

Collectively, these studies suggest enough good quality sleep is important for a healthy brain, and in particular for clearing toxins associated with dementia from the brain.

But we still don’t know if treating a sleep disorder or improving sleep more broadly affects the brain’s ability to remove toxins, and whether this reduces the risk of dementia. It’s an area researchers, including us, are actively working on.

For instance, we’re investigating the concentration of Aβ and tau measured in blood across the 24-hour sleep-wake cycle in people with sleep apnoea, on and off treatment, to better understand how sleep apnoea affects brain cleaning.

Researchers are also looking into the potential for treating insomnia with a class of drugs known as orexin receptor antagonists to see if this affects the clearance of Aβ from the brain.

If you’re concerned

This is an emerging field and we don’t yet have all the answers about the link between disrupted sleep and dementia, or whether better sleep can boost the glymphatic system and so prevent cognitive decline.

So if you are concerned about your sleep or cognition, please see your doctor.

Julia Chapman, Clinical Trials Lead and Postdoctoral Research Fellow, Woolcock Institute of Medical Research and Conjoint Lecturer, Macquarie University; Camilla Hoyos, Senior Lecturer in the Centre for Sleep and Chronobiology, Macquarie University, and Craig Phillips, Associate Professor, Macquarie Medical School, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Just like in the modern world, people in ancient times wanted to know how to live a long and healthy life.

Greeks and Romans heard fantastic tales of far-away peoples living to well beyond 100.

Greek essayist Lucian (about 120–180 CE) writes:

Indeed, there are even whole nations that are very long-lived, like the Seres [Chinese], who are said to live 300 years: some attribute their old age to the climate, others to the soil and still others to their diet, for they say that this entire nation drinks nothing but water. The people of Athos are also said to live 130 years, and it is reported that the Chaldeans live more than 100, using barley bread to preserve the sharpness of their eyesight.

This is how they thought this could happen.

Whatever the truth of these tales, many ancient Greeks and Romans wanted a long and healthy life.

An ancient doctor’s perspective

Ancient doctors were interested in what people who lived long lives were doing every day and how this might have helped.

The Greek physician Galen (129–216 CE), for example, discusses two people he knew personally in Rome who lived to old age.

First, there is a grammarian (someone who studies and teaches grammar) called Telephus, who lived to almost 100.

According to Galen, Telephus ate just three times a day. His diet was simple:

gruel boiled in water mixed with raw honey of the best quality, and this alone was enough for him at the first meal. He also dined at the seventh hour or a little sooner, taking vegetables first and next tasting fish or birds. In the evening, he used to eat only bread, moistened in wine that had been mixed.

Galen also tells us Telephus had some bathing habits that might seem unusual to us today. Telephus preferred to be massaged with olive oil every day and only have a bath a few times a month:

He was in the habit of bathing twice a month in winter and four times a month in summer. In the seasons between these, he bathed three times a month. On the days he didn’t bathe, he was anointed around the third hour with a brief massage.

Second, there was an old doctor named Antiochus, who lived into his 80s.

According to Galen, Antiochus also had a simple diet.

In the morning, Antiochus usually ate toasted bread with honey. Then, at lunch, he would eat fish, but usually only fish “from around the rocks and those from the deep sea”. For dinner, he would eat “either gruel with oxymel [a mix of vinegar and honey] or a bird with a simple sauce”.

Alongside this simple diet, Antiochus went for a walk every morning. He also liked to be driven in a chariot, or had his slaves carry him in a chair around the city.

Galen also said Antiochus “performed the exercises suitable for an old man”:

There is one thing you should do for old people in the early morning as an exercise: after massage with oil, next get them to walk about and carry out passive exercises without becoming fatigued, taking into account the capacity of the old person.

Galen concludes that Antiochus’ routine probably contributed to his good health well into advanced age:

Looking after himself in old age in this way, Antiochus continued on until the very end, unimpaired in his senses and sound in all his limbs.

Galen stresses that Telephus and Antiochus had some obvious things in common. They ate just a few times a day; their diet was of wild meats, whole grains, bread and honey; and they kept active every day.

What can you do?

Not all of us can live to 100 or more, as the Greeks and Romans were well aware.

However, Lucian offers us some consolation in his essay On Octogenarians:

On every soil and in every climate people who observe the proper exercise and the diet most suitable for health have been long-lived.

Lucian advised that we should imitate the lifestyles of people who have lived long and healthy lives if we want to do the same.

So, if you lived in Rome in the 2nd century CE, people like Telephus and Antiochus, who had a simple diet and kept active all their lives, would be good role models.

Konstantine Panegyres, Lecturer in Classics and Ancient History, The University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.