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.

It’s that time of year when many people are getting started on their resolutions for the year ahead. Doing more physical activity is a popular and worthwhile goal.

If you’re hoping to be more active in 2024, perhaps you’ve invested in an activity tracker, or you’re considering buying one.

But what are the benefits of activity trackers? And will a basic tracker do the trick, or do you need a fancy one with lots of features? Let’s take a look.

Why use an activity tracker?

One of the most powerful predictors for being active is whether or not you are monitoring how active you are.

Most people have a vague idea of how active they are, but this is inaccurate a lot of the time. Once people consciously start to keep track of how much activity they do, they often realise it’s less than what they thought, and this motivates them to be more active.

You can self-monitor without an activity tracker (just by writing down what you do), but this method is hard to keep up in the long run and it’s also a lot less accurate compared to devices that track your every move 24/7.

By tracking steps or “activity minutes” you can ascertain whether or not you are meeting the physical activity guidelines (150 minutes of moderate to vigorous physical activity per week).

It also allows you to track how you’re progressing with any personal activity goals, and view your progress over time. All this would be difficult without an activity tracker.

Research has shown the most popular brands of activity trackers are generally reliable when it comes to tracking basic measures such as steps and activity minutes.

But wait, there’s more

Many activity trackers on the market nowadays track a range of other measures which their manufacturers promote as important in monitoring health and fitness. But is this really the case? Let’s look at some of these.

Resting heart rate

This is your heart rate at rest, which is normally somewhere between 60 and 100 beats per minute. Your resting heart rate will gradually go down as you become fitter, especially if you’re doing a lot of high-intensity exercise. Your risk of dying of any cause (all-cause mortality) is much lower when you have a low resting heart rate.

So, it is useful to keep an eye on your resting heart rate. Activity trackers are pretty good at tracking it, but you can also easily measure your heart rate by monitoring your pulse and using a stopwatch.

Heart rate during exercise

Activity trackers will also measure your heart rate when you’re active. To improve fitness efficiently, professional athletes focus on having their heart rate in certain “zones” when they’re exercising – so knowing their heart rate during exercise is important.

But if you just want to be more active and healthier, without a specific training goal in mind, you can exercise at a level that feels good to you and not worry about your heart rate during activity. The most important thing is that you’re being active.

Also, a dedicated heart rate monitor with a strap around your chest will do a much better job at measuring your actual heart rate compared to an activity tracker worn around your wrist.

Maximal heart rate

This is the hardest your heart could beat when you’re active, not something you could sustain very long. Your maximal heart rate is not influenced by how much exercise you do, or your fitness level.

Most activity trackers don’t measure it accurately anyway, so you might as well forget about this one.

VO₂max

Your muscles need oxygen to work. The more oxygen your body can process, the harder you can work, and therefore the fitter you are.

VO₂max is the volume (V) of oxygen (O₂) we could breathe maximally (max) over a one minute interval, expressed as millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). Inactive women and men would have a VO₂max lower than 30 and 40 ml/kg/min, respectively. A reasonably good VO₂max would be mid thirties and higher for women and mid forties and higher for men.

VO₂max is another measure of fitness that correlates well with all-cause mortality: the higher it is, the lower your risk of dying.

For athletes, VO₂max is usually measured in a lab on a treadmill while wearing a mask that measures oxygen consumption. Activity trackers instead look at your running speed (using a GPS chip) and your heart rate and compare these measures to values from other people.

If you can run fast with a low heart rate your tracker will assume you are relatively fit, resulting in a higher VO₂max. These estimates are not very accurate as they are based on lots of assumptions. However, the error of the measurement is reasonably consistent. This means if your VO₂max is gradually increasing, you are likely to be getting fitter.

So what’s the take-home message? Focus on how many steps you take every day or the number of activity minutes you achieve. Even a basic activity tracker will measure these factors relatively accurately. There is no real need to track other measures and pay more for an activity tracker that records them, unless you are getting really serious about exercise.

Corneel Vandelanotte, Professorial Research Fellow: Physical Activity and Health, CQUniversity Australia

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

The human brain is remarkably complex, with trillions of connections that control how you move, think and feel.

Yet it’s still vulnerable to debilitating conditions such as paralysis, stroke, epilepsy and various neurodegenerative diseases.

Scientists are investigating if a kind of technology, known as the brain-computer interface, could help patients move and communicate better.

So how does it work? And what are the potential risks?

What is a brain-computer interface?

A brain-computer interface works by reading electrical signals produced by the brain, which it translates into digital signals that an external computer can understand. The computer then sends instructions – such as the command to move a cursor, steer a wheelchair or read a sentence aloud – back to the brain. This whole process happens in real time, allowing patients to do tasks more independently.

There are two types of brain-computer interfaces:

Non-invasive

Non-invasive brain-computer interfaces are worn externally, usually in the form of electroencephalogram headsets. An electroencephalogram, or an EEG, is a type of test that measures activity in the brain. This technology is already available on the consumer market, found in everything from meditation apps to video games.

Invasive

Invasive brain-computer interfaces are surgically implanted. This involves placing electrodes – devices that carry electrical signals from the body to medical instruments – directly onto the exposed surface of the brain. These interfaces aim to help restore key functions such as speech and mobility in people with a disability, caused by conditions such as stroke or spinal cord injury.

It is this second category that’s attracting attention from investors and scientists. Several companies – including early developer Blackrock Neurotech, Australian-owned Synchron, and Elon Musk’s Neuralink – are racing to get implantable brain-computer interfaces to patients.

Under current regulations, only a handful of clinical trial participants globally can access this technology. But this may change as interest grows. The international brain-computer interface market is expected to be worth roughly A$14 billion by 2033, up from its current value of just under $3 billion.

Their role in health care

Brain implants may sound dystopian, but they are a promising part of neuroscience research.

More than three billion people worldwide live with a neurological condition that affects their motor, communication or sensory functions. Examples include stroke, epilepsy, Parkinson’s disease, cerebral palsy and traumatic brain injury.

Brain-computer interfaces are particularly helpful for communication. In one 2023 study, paralysed patients that used a brain-computer interface were able to communicate up to 78 words per minute. That’s a five-fold improvement from the 15 words per minute achieved by patients in 2021. And recent research shows this technology is still rapidly improving.

Beyond communication, surgeons are using brain-computer interfaces to map brain activity in real time. This is particularly useful during complex or high-risk procedures, where surgeons must protect key brain regions.

Sleep researchers are also using this technology to analyse brain signals in people who may have a sleep disorder, such as insomnia or sleep apnoea. Brain-computer interfaces may be a more accurate way to diagnose and treat such disorders, compared to other methods such as sleep diaries that rely on participant reports.

Scientists are also investigating how these interfaces could be used in rehabilitation, particularly for people with conditions such as depression, epilepsy, stroke and Parkinson’s disease.

What are the risks?

Here are three worth noting.

Physical harm

Any kind of brain implant can cause physical damage that may affect how neighbouring brain regions work.

For example, if there’s bleeding in a part of the brain that controls speech or movement, even a small blot clot could impair those functions. And while infections in the brain are rare, they can cause swelling and further complications if not immediately treated.

Research suggests there are long-term effects of having foreign material inside the skull. Over time, the brain treats the implant as an intruder, forming scar tissue around it in a bid to destroy nearby brain cells and stop the implant from working. Regular movements such as breathing may also create friction between the hard implant and soft brain tissue, causing some brain regions to become inflamed.

Cybersecurity threats

One recent study found a large-scale breach of brain-computer interface systems could theoretically allow hackers to access sensitive neural data, such as patients’ thoughts and memories. Hacking may also enable them to impair a patient’s cognitive functions such as the ability to concentrate, or even manipulate motor signals to affect how well they move. That’s a scary prospect, especially if these devices become more common in health care and other sectors. In the United States, some jurisdictions are already working to protect neural data rights in law, but there are still major regulatory gaps.

Unequal access

Currently, getting a brain implant will set you back between $50,000 to $140,000. That doesn’t include the cost of ongoing maintenance and follow-up care. So ordinary patients are unlikely to access this technology anytime soon, widening the gap between who can and can’t afford to improve their health.

Where to next

Brain-computer interfaces are a promising new technology, but they come with risks.

We urgently need more high-quality research into the long-term effects – both physical and psychological – of permanent brain implants. Importantly, this research should be funded publicly and not just by a handful of large, profit-driven companies.

David Tuffley, Adjunct Senior Lecturer, Applied Ethics and CyberSecurity, Griffith University

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