Sleep Apnoea, Memory and Dementia Risk

Sleep apnoea affects millions of people and is often associated with loud snoring, disrupted sleep and daytime tiredness. But could it also influence memory and dementia risk?

In this episode of Brain Matters, host Neil Broomfield speaks with sleep scientist Samantha Bramich about a recent Australian study that found people with obstructive sleep apnoea performed worse on memory tests and had a higher burden of dementia risk factors. Together, they unpack what the research found, explore possible links between sleep and brain health, and discuss why it's important to look beyond the headlines.

The conversation also covers common signs of sleep apnoea, current treatment options, and what this study can and cannot tell us about dementia risk.

Listen now to learn more about the role of sleep in brain health and why addressing sleep concerns may be an important step towards supporting your overall wellbeing.

Based on:

Article: Sleep Apnoea Tied to Memory Loss, Dementia Risk in Midlife

Paper: Associations of self-reported obstructive sleep apnea with cognition and dementia risk in cognitively unimpaired middle-aged adults 

Brought to you by the ISLAND Project and Wicking Dementia Research and Education Centre at the University of Tasmania. To continue the discussion and for more information visit https://island.mooc.utas.edu.au or email island@dementia.utas.edu.au

Transcript

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Neil Broomfield: 00:03

Hello and welcome to Brain Matters, where we look beyond the Brain Health headline and go deeply into what research really means for you. I'm Neil Broomfield. And today we're discussing a topic that affects millions of people, but often flies under the radar when we talk about brain health, and that's sleep apnoea. 

This topic was emailed in to us by Anne, one of our island participants. And thanks for submitting this question. We shall try to cover this as thoroughly as possible. This article relates to a recent Australian study from Monash University, which found that people with obstructive sleep apnoea performed worse on memory tests and carried a greater burden of dementia risk factors. The findings led to headlines suggesting that sleep apnoea may increase dementia risk. 

But what exactly is sleep apnoea? How might it affect the brain? And what can we actually conclude from this study? To explore the findings in depth, I'm joined by sleep scientist and researcher at the Wicking Dementia Research and Education Centre, Samantha Bramich. Welcome, Samantha. It's lovely to meet up with you again.

Samantha Bramich: 01:17

Thanks, Neil. It's great to be here.

Neil Broomfield: 01:19

Right, let's start at the beginning. What exactly is obstructive sleep apnoea and how common is it?

Samantha Bramich: 01:26

So obstructive sleep apnoea or OSA is one of the most common sleep disorders we see. It happens when the muscles in the throat relax too much during sleep and they cause the airway to repeatedly narrow or collapse. As a result, breathing can briefly stop or become very shallow, often many times throughout the night. Each time that happens, the brain has to briefly wake the body just enough to reopen the airway. So most people don't actually remember these awakenings because they're called micro-awakenings, but they fragment the sleep and they reduce the amount of restorative sleep we're getting. So the classic symptoms are loud snoring, witness pauses in breathing, gasping or choking during sleep, and also feeling excessively sleepy during the day. But it's important to remember that not everyone who snores has sleep apnoea, and many people with sleep apnoea don't realize they have it until a bed partner notices the symptoms or they're referred to for a sleep study. So it's actually a really common condition, particularly in middle-aged and older adults. And many cases do remain undiagnosed because people don't realize it's happening. 

There was a recent big study done in 2025 looking at the burden of obstructive sleep apnoea, and it found that globally people over the age of 50, about 43% of men and 28% of women have obstructive sleep apnoea. So it is quite common. And that's one of the reasons that there's so much interest in understanding not only its impact on daytime function and cardiovascular health, but also whether it may have implications for long-term brain health.

Neil Broomfield: 02:57

You talked about some numbers there, Sam. Is it true that old folk really do need less sleep as they get more aged and why?

Samantha Bramich: 03:06

So it's a bit of a fallacy that as you get older you need less sleep. By the time we reach our adult years, it's recommended that we have between seven and nine hours sleep. Sometimes the research shows that older people have less sleep, but that's not because they need less sleep. It's actually because as we get older, our sleep stages and our overnight sleep changes so that we end up having a lot more light sleep compared to deep sleep. So we often wake up a lot more overnight as well, which causes us to have less sleep, less restorative sleep as we get a bit older.

Neil Broomfield:

I thought it was partly because you need to go to the loo more often!

Samantha Bramich:

That also comes into it. So that's one of the other things that comes into causing us to wake up more overnight than we used to when we were younger.

Neil Broomfield: 03:49

That's no myth.

Samantha Bramich: 03:51

Not at all. No.

Neil Broomfield: 03:52

That's very interesting, Sam. So sleep apnoea isn't simply about snoring. Oh, and incidentally, as a sideline, it's a very strange word, apnoea. So I looked up its derivation and it comes from the Greek. And the translation is roughly absence of respiration. So it's a very apposite word.

Samantha Bramich: 04:12

It is, indeed.

Neil Broomfield: 04:13

It's a medical condition that repeatedly disrupts breathing and sleep throughout the night, sometimes without a person even realising that it's happening. Now, what first sparked researchers' interest in the connection between sleep and dementia?

Samantha Bramich: 04:28

Well, over the past 20 years, there's been a lot more uh research into sleep than has ever been done before. And we've learned that sleep is far more than just a period of rest. It's not a period where we're unconscious. There's actually a lot of biological processes happening during sleep that are really essential for healthy brain and body function. So we know that sleep plays an important role in consolidating memories, supporting learning, and maintaining normal brain function. But experimental research has also suggested that sleep supports the brain's normal housekeeping processes, including the clearance of waste, although exactly how this relates to dementia in humans is still being investigated. So at the same time, a growing body of research has shown that poor sleep and several sleep disorders are associated with cognitive decline and dementia risk. And that naturally raises the question of whether conditions like obstructive sleep apnoea might contribute to these processes, either directly or indirectly. And that's really where studies like this one fit in. They're helping us better understand those relationships between sleep and health.

Neil Broomfield: 05:30

You said, I think, um, that sleep helps you to clear the brain, to clean it. How does it do that?

Samantha Bramich: 05:38

It's well, I'm not 100% across the whole system, but it was discovered in the last 10 years and it was termed the glymphatic system. So as we're sleeping, there's a sort of a washout process that happens within the brain where it clears it of all of the waste that accumulates during the day. So those sort of unneeded fragments of cells and things that die off in the natural process of our daily activities, they all get washed out. And we think that that helps keep the brain healthy. And so when we're not sleeping as well, that process doesn't happen as efficiently or as effectively as it should be, which might lead to the build-up of some of these proteins and things that can lead to dementia in the long term. Proteins like tau, amyloid plaques, and alpha synuclein.

Neil Broomfield: 06:28

I think this cleaning out um actually refers mostly to the amyloid, doesn't it? Is that right, or is it all of them?

Samantha Bramich: 06:36

It's a lot of different ones, yeah, yeah. But I'm not I'm not 100% sure on the specifics of them, but it is a lot of different sort of yeah, waste products that get cleared out.

Neil Broomfield: 06:45

And there's a lot to learn about this even yet.

Samantha Bramich: 06:47

There is, it’s still a very new research area.

Neil Broomfield: 06:57

Yes, yes, good point. So while we're on this kind of vein, forgive the pun of discussing this, is there more than one type of sleep apnoea, Sam?

Samantha Bramich: 07:09

There is. There's a couple of different types. So obstructive sleep apnoea is the most common one, and that's where you have pauses in your breathing due to a restriction or collapse of the airway. There's another type of sleep apnoea called central sleep apnoea, and that can be caused by changes in brain function or changes in the cardiovascular or heart function system. So that also causes pauses in breathing, but not due to a blockage in the airway. So that's not as common and it tends to be more associated with medical, other medical sort of conditions. It's also actually common in babies. So we do see central sleep apnoea in babies because their respiratory system isn't fully uh functional or evolved yet. So sometimes you might hear pauses in babies' breathing, which is very normal. It can cause worry sometimes, but that's another form of central sleep apnoea.

Neil Broomfield: 08:02

That sounds scary if you're a new parent and you had no idea. Now, when I've talked about this with other folk, um the expression the chain-stokes respiration comes into play sometimes. Can you explain to me what that is?

Samantha Bramich: 08:18

So Chain-Stokes breathing is a pattern of breathing that's mediated by the cardiovascular system where it's not quite a pause in breathing, but it's a waxing and waning. So the breathing will get shallow and then it'll get higher, faster again, and shallow again. And so it's a sort of a pattern of breathing that tends to be related to heart failure or certain heart conditions.

Neil Broomfield: 08:45

Sam, that gives us a very nice background to get on with. So now should we talk about the new Monash University study that generated these headlines? What did the researchers actually do?

Samantha Bramich: 08:59

So this was a large Australian study involving nearly 2,800 cognitively healthy adults aged between 40 and 70 who were participating in the Australian Healthy Brain Project. The researchers compared participants who reported having obstructive sleep apnoea with those who didn't. They looked at performance across several computerized cognitive tests, so memory tests, and they focused mainly on memory, and they also calculated each participant's dementia risk score. So that's a validated score that estimates future dementia risk on several well-established risk factors, including blood pressure, cholesterol, body weight, physical activity, and education. Alongside that, they actually also looked at genes, so specifically at people who carried the ApoE4 gene, which we know is associated with a higher risk of developing Alzheimer's disease, and whether those that gene influenced the findings as well.

Neil Broomfield: 09:52

And as a side note to our listeners, the ApoE protein and its probable influence on the contributive development of Alzheimer's was examined in detail in a previous Brain Matters podcast with Professor James Vickers. So back to what you were saying, Sam, what were the major findings of this research?

Samantha Bramich: 10:10

So it was a really interesting study because the researchers found that people who reported having obstructive sleep apnoea generally performed worse on the memory test than those without sleep apnoea. They also tended to have a higher dementia risk score, meaning that they were more likely to have recognized dementia risk factors such as obesity, hypertension, and high cholesterol. But one finding that attracted particular attention was that participants who reported untreated sleep apnoea had poorer memory function than those who reported receiving treatment. And interestingly, the treated group also performed similarly to participants without sleep apnoea. So that was really interesting because they found people who were treated for sleep apnoea had better scores than people who weren't treated. But the researchers also found that carrying the ApoE4 gene didn't appear to alter these relationships. So within the study, the associations between sleep apnoea and memory look similar regardless of people's genetic risk.

Neil Broomfield: 11:08

When I've looked at this question of memory performance and kind of taken a backseat look at how you can improve it, it seems that it's not only the practicing and developing, but it's the repeat of what you're doing and kind of top-up courses and what you've already done that kind of reinforce it. Just a side issue, but I found that rather an interesting observation. Well, anyway, Sam, at first at first glance, that's a pretty striking finding. Does this study actually show that sleep apnoea causes dementia?

Samantha Bramich: 11:47

That's a really good question, Neil, because from the headlines it seemed that that might be the case, but it's actually not, and I think that's probably a single most important message from this study. So it was an observational study, and that tells us that two things are associated with one another. It doesn't actually tell us that one caused the other. So what we can say is that people with sleep apnoea tended to have poorer memory performance and carried a greater burden of recognised dementia risk factors. But what we can't say is that the sleep apnoea itself causes dementia or that treating sleep apnoea will prevent dementia. So to answer those questions, we need long-term studies that follow people over many years, or intervention studies that examine whether treating sleep apnoea changes those cognitive scores. So this study, it provides a really important piece of the puzzle, but it isn't the final answer yet.

Neil Broomfield: 12:40

And one interesting finding was that the relationship between sleep apnoea and memory became weaker after researchers accounted for vascular risk factors. Vascular. We'll come back to that, Sam. But why is that important?

Samantha Bramich: 12:55

I actually think that's one of the most informative findings in the paper. So once the researchers adjusted for those vascular risk factors like obesity, hypertension, and cholesterol, the relationship between sleep apnoea and memory became much weaker. And this suggests that some of what we're seeing may be explained by these conditions, which do commonly occur alongside sleep apnoea. So those same vascular risk factors are already well-established contributors to dementia risk. We know that, you know, obesity and hypertension untreated are risk factors for Alzheimer's and other dementias. So rather than thinking about sleep apnoea in isolation, it's probably more accurate to think about it as one part of a broader picture of brain and cardiovascular health. So I guess it kind of reminds us that healthy aging is influenced by multiple factors, and improving brain health is likely to require addressing several of those modifiable risk factors we know about rather than focusing on just one.

Neil Broomfield: 13:52

Okay. Now can we go back to the question vascular? What exactly is that?

Samantha Bramich: 13:58

So we did have a look at this beforehand, just so that we could get um a good definition out there. But when we think about vascular health, it tends to be about how well your body's network of blood vessels, so things like your arteries, veins, and capillaries, how well they're functioning to deliver oxygen and nutrients while clearing out waste. So it's about how the blood is circulating throughout our body, I suppose.

Neil Broomfield: 14:22

A kind of generic term for your veins and arteries and all the rest of it, the lymph’s and so on and so forth.

Samantha Bramich: 14:28

All of those things.

Neil Broomfield: 14:29

Very interesting. Researchers often talk about biological mechanisms. So what are some of the possible ways that sleep apnoea could affect the brain?

Samantha Bramich: 14:40

There's several biological plausible mechanisms, although it's important to emphasize that they are still being investigated. We really don't know enough about the links between sleep and dementia. But one possibility is intermittent hypoxia. So during sleep apnoea, when we have those repeated pauses or cessation of breathing, oxygen levels can repeatedly fall and then recover throughout the night. So there is some research that suggests that this might contribute to what's called oxidative stress or inflammation in the brain and body, which might lead to dementia over long term. Another mechanism is chronic sleep fragmentation. So even if someone spends eight hours in bed, those repeated brief awakenings overnight due to the breathing trouble in sleep apnoea reduces the amount of restorative sleep, which is really important for memory consolidation and other brain functions as well. So some researchers have proposed that sleep apnoea may affect vascular health and potentially influence some of the brain's normal maintenance processes. But at this stage, we know these mechanisms are plausible, but we're still working to understand exactly how they contribute to the long-term cognitive and brain health in people.

Neil Broomfield: 15:54

And one part of the study I found particularly interesting was the finding around treatment. What should listeners make of that?

Samantha Bramich: 16:02

I think it's a really encouraging finding, Neil, but it's also one that should be interpreted carefully. So participants who reported receiving treatment for sleep apnoea performed similar on memory testing to people who didn't report having sleep apnoea. So that's certainly reassuring.

Neil Broomfield: 16:20

What treatment?

Samantha Bramich: 16:21

Treatment, yes, that's a great question. So there's a few different treatments for sleep apnoea. The most common is CPAP, which is continuous pressure air positive airway pressure, which is where you wear a mask over your nose or mouth that pumps some air into your airway to keep it open overnight. So that's the gold standard treatment, which will stop any collapsing of the airway overnight. There are other treatments such as oral mandibular devices, which is sort of like these little mouth guards that you can pop in overnight, which change the jaws position slightly, which can alleviate sleep apnoea in some people. There's also positional therapy. So a lot of people will have sleep apnoea worse when they're lying on their back, so they can have sort of a device that keeps them on their side to stop some of that apnoea. But the only way to really know where the sleep apnoea is coming from and what treatment is best is to have a sleep study and trial some of these devices to see what works best for you, because it can be quite individual as to what's causing sleep apnoea as well.

Neil Broomfield: 17:24

I'm glad you brought up the question of sleep study, because I think I've seen these CPAP machines available for sale. And does that infer that you can actually go and buy one before being studied? And if that is the case, would that be a sensible thing to do?

Samantha Bramich: 17:43

I think that would be a good idea if you have clear evidence that you stop breathing in your sleep. A CPAP is only going to help. It's not going to make anything worse. The thing is, it's good to see a provider of a CPAP before you start therapy because they can start it on a certain pressure for you. Often that pressure is determined by a sleep study. So the pressure involves how much air is being pushed into your airway. And to know what air pressure is best for you needs to come from a sleep study. Often they'll start at a very low pressure if you haven't had a sleep study, and that's often enough to alleviate some of the symptoms. But the ideal way is to have a sleep study and then proceed to CPAP after that so you can get the best treatment for you.

Neil Broomfield: 18:31

Or perhaps one should say, if you've any doubt at all, go and see your GP first.

Samantha Bramich: 18:36

Definitely. That's always the first step. And they can direct you in the right place.

Neil Broomfield: 18:40

Right. So I think the takeaway there is don't go and buy one on your own without consulting some sort of expert.

Samantha Bramich: 18:47

True. And you don't know how well they've been looked after if you're buying one off Gumtree or Facebook.

Neil Broomfield: 18:51

Sam, I think that listeners are probably now wondering whether they might have sleep apnoea. What signs should they look out for?

Samantha Bramich: 18:59

Yeah, so the most common signs that people recognize for sleep apnoea is loud, persistent snoring that coincides with pauses in breathing. And it's usually a bed partner that will notice this because obviously when we're sleeping and snoring, we can't hear it, we don't know. So many people don't realise it's happening. It can also come along with waking up gasping or choking, though. So if you do wake up with a really dry mouth or coughing or like a feeling that you were choking in your sleep, that's a big sign that there might be some sleep apnoea going on. Along with excessive daytime sleepiness and morning headaches. So a lot of people who have untreated sleep apnoea do wake up with a really bad morning headache because of the change in oxygen overnight and because they haven't had the restorative sleep due to waking up multiple times a night, they often feel really sleepy during the day. So they're probably the biggest signs. Some people also describe difficulty concentrating, poor memory, or simply never feeling refreshed despite spending a lot of time in bed. So some people might sleep eight to ten hours, but they don't wake up feeling refreshed, and that's often a big sign that there's um possibly sleep apnoea going on. So I guess if those symptoms sound familiar, it's worth speaking to your GP because they can assess your symptoms and they know your medical background. So they can determine whether you should go and have a sleep study. But the important thing I think to remember is that sleep apnoea is quite common and for most people it is very treatable.

Neil Broomfield: 20:29

We're talking here largely, I suppose, in the initial stages to a local audience in Tasmania. Is it easy to get us into a sleep study here?

Samantha Bramich: 20:41

It is relatively easy to get into a home-based sleep study in Tasmania. We do have a couple of private companies that offer those in the big cities in Hobart and Launceston. There's not actually a functional sleep lab at the moment, from my understanding, but home-based sleep studies are able to detect sleep apnoea. So they're a really good option, especially in our regional cities where we don't have access to those big, large clinical medical centres.

Neil Broomfield: 21:10

And would you need a referral or should you anyway get a referral from your GP first?

Samantha Bramich: 21:15

I believe you do need a referral, yeah. Because they do ask about other underlying health conditions, and then they take that into the results of the sleep study after you've had one as well.

Neil Broomfield: 21:25

That's very helpful. Well, finally, Sam, what would you say are the key takeaways from this research?

Samantha Bramich: 21:33

I think the key message is that sleep is a really important pillar of brain health. And this study from Monash, it adds it to the growing body of evidence linking obstructive sleep apnoea with poorer memory and a greater burden of dementia risk factors. But at the same time, I think it's equally important not to overstate what the study shows. So it doesn't demonstrate that sleep apnoea causes dementia, nor does it prove that treating sleep apnoea will prevent dementia. But what it does reinforce is the importance of recognizing and managing sleep apnoea, because we know that not only it can improve sleep quality, daytime functioning, and cardiovascular health, but because maintaining good sleep is also likely to be one part of supporting healthy brain aging in general. So I think as researchers, we're increasingly recognizing that dementia prevention isn't about one single factor, as I mentioned before. It's about looking after the whole person, including our cardiovascular health, our physical health, our diet, hearing, and importantly, sleep. So this study provides a really valuable piece of that much larger puzzle, but we're still trying to figure out how sleep plays a role in our long-term brain health. And we're going to get there, but we need a lot more research before we completely understand its role in our brain.

Neil Broomfield: 22:49

Sam, what a fascinating expose on the whole question of sleep. I've really enjoyed talking to you, and thank you so much.

Samantha Bramich: 22:58

Thanks so much for having me, Neil.

Neil Broomfield: 23:00

It's easy to see a headline about dementia risk and jump straight to worst-case conclusions, but studies like this remind us that brain health is complex. This research suggests that sleep apnoea may be associated with poorer memory and a higher burden of dementia risk factors, particularly in midlife. But it doesn't show that sleep apnoea directly causes dementia. What it does highlight is the importance of looking after our sleep and talking to a healthcare professional if we have concerns about symptoms. 

Thanks for joining us for another episode of Brain Matters. And as always, I need to thank our technical producer Drew Stansbury and our program producer Florence Sward for making this series of podcasts possible. If you've enjoyed today's discussion, please subscribe, leave a review, and share the podcast with someone who might find it helpful. 

Until next time, take care of your brain health and bye bye for now.