PsychTalksManaging pain can be part of life for many of us. Professor Amy Jordan and Associate Professor Natalia Brumley unlock the intriguing relationship between sleep and pain. Find out how different types of pain affect sleep quality, if gender is a factor, and in what ways exercise, blue light and social media consumption might have an impact.
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From the Melbourne School of Psychological Sciences at the University of Melbourne. This is PsychTalks.
Hi and welcome again to PsychTalks. I'm Associate Professor Cassie Hayward and I'm here with my co host, Professor Nick Haslam. Hi, Nick.
Hi Cassie. Great to be here. And as we do on PsychTalks, I'm really looking forward to diving into another fascinating journey into psychology research from the University of Melbourne's School of Psychological Sciences.
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Yeah, or get the word out by sharing episodes with workmates, friends and family. OK, so today we're looking at something that can affect many of us at some stage of life: pain and its complex relationship with sleep. To guide us through their very insightful research on this, we're joined by Professor Amy Jordan and Associate Professor Natalia Brumley. So, Amy, you run a sleep lab, and you do research on sleep as you say, Can you tell us what a sleep lab actually is and how you study people while they're asleep? I mean, how do they fill out their questionnaires?
Yeah, well, that's an interesting question, Nick. So, the sleep lab, to start with, is basically some bedrooms that have a normal bed and a bedside table, but just a little bit of equipment, and then outside of the bedrooms, we have a monitoring area with a bunch of computers. So, of course, people aren't filling out questionnaires while they're asleep. But what we do is we typically put electrodes on their face and on their head just on the surface of their skin. And then they plug into the equipment next to their bed so they can still roll around and move around. Often, it does take people a few minutes longer to go to sleep, but then once they're asleep, we can see that on the monitoring room. And we can either do nasty things like play auditory tones to wake them up. Or we even have a vibrating device that goes under the pillow. Uh, so that we can disturb their sleep sometimes without them even knowing it and then look at the consequences either for the brain or the body.
I have three young kids who often end up in our bed. So even with all that going on, I think my husband would happily volunteer for any sleep related studies you've got going on. So that gives us an understanding of how you study sleep. But I know one of the things you've been exploring lately is the relationship between pain and sleep, and maybe just to start off. I know people kind of have an understanding of what pain is. But Natalia, if you could just give us some proper definitions of maybe chronic and acute pain to kind of set us on the way.
Yes, sure. So, the official definition of pain is that it's an unpleasant sensory or emotional experience, and that is associated with or resembling that associated with actual or potential tissue damage. So here we are, talking about tissue damage, so pain in principle is very useful. It helps us prevent further injury, however often once the trigger is off. So, there is no pain. Uh, there shouldn't be any pain, it can persist. And if pain lasts more than about three months, that's what we call chronic pain. What is really happening with the transition from acute to chronic pain is that often you experience this so-called pain sensitisation, which is when the central nervous system undergoes the changes and becomes more sensitive to pain. And even something that's not meant to be painful or not very painful becomes painful for that. And here I feel I should say that this is exactly what we do in our lab. We measure pain sensitivity, so whether your response to pain is more amplified or normal, and we do it in a variety of ways. So, we induce pain. So, either heat pain or pressure pain or a cold pain. And then we look at what point a person says, "This is painful." So, what is their pain threshold? And the higher the pain threshold, the less sensitive you are and the opposite.
Do people differ in their pain thresholds or pain sensitivity? Are there common themes in who will press that button that it hurts sooner rather than later?
Yes, absolutely so the age, sex and personality, even, is the predictor of how sensitive to pain you are. For example, females are a lot more sensitive to pain, and then people who actually have chronic pain conditions are known to have increased pain sensitivity again due to pain sensitisation. Women are also more- they feel more pain because they amplify the emotional aspect of it.
That's really useful background, those definitions of acute and chronic pain and how they are related. Very useful background, I'm sure for where we are going with this. So, can you tell us a bit about the relationship between sleep and pain? I guess, intuitively, you'd imagine that if you're experiencing chronic pain, of course it will be harder to get to sleep. But I imagine the story is more complex than that.
Yes, indeed. A very high percentage of chronic pain patients find it difficult to sleep, so they experience some sort of sleep disruption. But what one of the earlier studies by Edwards and colleagues in 2008 showed that the effect is bidirectional. So what they did is they called almost 1000 people a few days in a row, asking them how many hours they slept and how much pain they were experiencing, how many symptoms of pain they could report. And then they did some sophisticated statistics and what they found that obviously the amount of pain predicted some sleep disturbance the following night. But importantly, a lot of the effect came from the night before. So, those who slept less than six hours or more than nine hours reported more pain the following day. And in our own work, we work with experimental pain. So not these natural fluctuations in people's pain symptoms but rather pain sensitivity. And what we were interested in is whether there are any studies that already have been done in the lab that would look at what was happening with the sleep before the pain measurements and how that affected the pain measurement. And our- Amy and I have this amazing PhD student, Shima Rouhi, who did a systematic review where she looked at the effects of total sleep deprivation, where you do not sleep at all, or sleep restriction where you sleep fewer hours than you normally would, and then sleep fragmentation where you are waking up in the middle of the night multiple times and looked at how that was affecting the pain threshold, which I mentioned different types as well as the more dynamic pain measures how much pain people experience when they receive a repeated stimulus. So, whether the pain increases and how much of the pain inhibition or reduction in pain they get when they get two stimuli, pain stimuli at once. Looking at those different pain measures, Shima found that there was indeed a lot of change, especially due to sleep. Total sleep deprivation. So, it does affect your pain, the morning after.
Wow. And so also, it's so handy to know that sleep quality is not just how much you're getting, but there are other parameters involved as well. So, are we talking here only about people who are experiencing clinically diagnosed pain or sleep problems? Or is this something that could also affect people who are just doing shift work or having reduced sleep because they've got young children or things like that?
Yeah, so certainly with shift work, it's well known that they have increased rates of chronic pain problems. How much of that is due to the sleep? You know, the poor sleep that they're getting even if they're sleeping during the day, often their sleep is not as good. They might have, you know, a bit of a sleep during the day and then a nap before they go on to work at night. But they also have lots of other problems as well, so there's higher rates of obesity. They often eat at abnormal times, which means that they have a higher rate of all sorts of cancers and diabetes and things as well. And so how much of the pain- increased rate of pain problems they have is due to the sleep? It's probably all interrelated, but- but it is certainly true. And the broader question we know even healthy young university student like we study in our labs. If we disrupt their sleep, their pain processing is altered the next day as well. So, it does seem to be a broader than clinically defined pain and sleep problems.
Are there other differences that come into play? So, you mentioned before, some gender and age differences in pain? So, did those demographic groups play out in terms of a difference in how sleep and pain interact?
Yeah, that's exactly what our PhD student Shima. Her meta-analysis showed that how sleep influences pain depended in the studies on how many women were in the studies. So, if you had a study that was all women, then their sleep-pain relationship was really clear. If you had a study with 50-50 or with more men than women, then this relationship appeared to be somewhat different, and age was another factor. So, the same factors that contribute to your pain sensitivity seem to be altering the sleep-pain relationship as well.
I should also mention that a lot of the pain disorders are predominantly women- occur in women, for example, osteoarthritis, migraines or fibromyalgia. You mostly have women affected and, interestingly, there has been not as much research done in women specifically, up until you know, 50 years ago, there would be mostly men tested because of the belief that menstrual cycle affects pain, which it does. But so, women were often not included in clinical trials. The same is, animal work has been mostly done in male rats or male mice and not female ones. So, a lot of the treatments that have been discovered have actually not been tested in women or have been predominantly following the pathways that are more true for men than women.
That's changing now, right?
That is very much changing and in fact, 2024, for the Association- Association for the Study of Pain, the International Association for the Study of Pain is the year of gender and sex differences in pain. There is also a lot of difference in government policies, and there is the Victorian sex pain gap occurring at the moment. So, there is a lot of interest in sex differences in pain. But there is definitely a gap, and there is definitely the niche there to address.
Do we know why there are these differences?
There is a lot less research on that, but we understand that there could be a few mechanisms and there could be psychological mechanisms. I already mentioned that there is this tendency for women to express their pain more readily, and there is this thought that men tend to withhold expressing pain. There is some research coming through that there could be different nociceptors depending on sex, and they act with different mechanisms again to create this relationship between sleep and pain. There are some studies also in neurobiology that differ. So, some neuroimaging evidence to suggest that different neural pathways are processing pain in men and women. So, there are some preliminary work that's being done, but nothing is 100% sure. But obviously, the hormonal effects are important. And that's something that we are starting to look at in our collaboration with Amy, our student is now looking at how pain sensitivity changes over the cycle. So, over the course of the cycle, that's some work that's currently in preparation.
And I guess it goes a little against conventional wisdom when you think about the pain women go through in childbirth and these other kind of experiences that women have that we kind of feel like we can cope with that pain that. But you're saying that's not really
Well, I think it's important to remember that pain sensitivity and pain tolerance are different things as well. So just because you change, you know, a heat stimuli changes from feeling warm to painfully hot more soon doesn't mean that you can't tolerate that pain and put up with it. So there are distinctions and we can measure those experimentally in the lab.
What is important is to keep in mind that certain things could predispose you more to the development of chronic pain and try to reduce those effects and sleep appears to be one of those.
I guess one thing people think might be helpful here is if they can improve their sleep by maybe exercising more. That might perhaps have benefits for their pain. Is that credible?
The evidence that exercise objectively changes sleep. People feel like they sleep better after they've done a good amount of exercise. They've done a marathon or something. You know, it can feel like you're sleeping. The evidence is that objective sleep, as we measured- would measure in the lab is not actually that greatly altered. In fact, if you take people who don't exercise and get them to run a marathon on a treadmill, then actually sleep can be impaired, probably because they're in a bit of pain, right? Their muscles are going, "What on the earth happened?" So, the- how exercise is changing sleep is not as sort of marked as you would think. Yeah.
Whereas exercise would be one of the go-to strategies for pain management in a lot of pain conditions, for example, osteoarthritis and that is known to improve your physical pain. But too much exercise can also make it worse. So, there is no direct linear relationship between the amount of exercise and the reduction in pain. It's all quite complex.
And Amy one thing I know a lot of people get hung up on these days is tracking their sleep with their smart watches. And I'm guilty of this. And I must say, I get really angry with my watch when it casually suggests I have a nap at 3 p.m. Or maybe I need more sleep tonight. So I think there's a very complicated relationship with our trackers. But as sleep researchers, what do you think about this tendency to people to track their sleep? And the first thing they look at in the morning is how their their watch said they slept. How does that impact our feelings about sleep?
Yeah, So given that the prevalence of insomnia is so high in the community, I think the watches and you know devices that can measure sleep in the home now can be problematic. So if people are waking up and you know, stressing that they didn't get sufficient sleep and oh, I better go to bed early tonight and develop anxiety about their sleep, then, of course, it can be completely counterintuitive. On the other hand, I think if somebody is feeling sleepy throughout the day, they're not really sure. Is this just old age? And my kids, you know, been in the bed all night long? Is that why I'm not feeling refreshed when I wake up in the morning? Then the watches can be useful if they show that, you know, actually, you know what? You didn't go to bed till 1 a.m. last night and you were up at five. Presumably you don't need a watch to tell you that, but for some people, it can be insightful into their own sleep habits. But I do think it's more likely that it's causing stress and anxiety and certainly GPs and sleep physicians are reporting more and more people are coming in, "My watch says this. What do I do about it?" And the reality is, in many cases, those people might not have problems at all.
And it seems very precise and accurate. It says, "You've got this much REM sleep, this much deep sleep." Is that an accurate reflection of your sleep, or is there still some..?
So the different devices have been validated against sort of the sleep study like we do in the laboratory. Some of them are reasonably accurate, but I think the difficulty is because these are commercial products, they're being- Their algorithms are being updated and changed all the time. And so, even if last year your particular brand of watch was observed to be, you know, quite accurate, you've got no idea what's happened to the algorithms between then and now. They really, they are based on heart rate, most of them these days movement, of course, but then heart rate, and then they can derive respiration rate from the heart rate signal as well. So that's what most of them are using.
Speaking of tracking your sleep, there have been studies not in pain but in cognitive performance, where people were told that they either slept well, for example, with a particular sleep stage. They had enough sleep in that stage or not enough, and after that they measured the participants' cognitive performance, and those who were told that they slept poorly actually performed worse than those who were told that they slept well. So, this is important to keep in mind that this subjective information is almost more important than the objective information from your watch that might make you feel worse than you actually do feel.
And Natalia, just to clarify that the information they received about their sleep was not necessarily true?
That's right. That was a complete placebo-nocebo type of scenario where the information was irrelevant. They were either told that they slept well or slept poorly. It had nothing to do with their actual quality of sleep. In fact, all of them slept well that night.
So much about sleep and pain is subjective perceptions. The subjective perceptions don't necessarily map directly onto the objective truth anyway. And maybe the subjective perceptions are just as important in some ways. So I guess the other thing that gets a lot of attention these days is not just screen time and monitoring watches and things like that, but also specifically blue light. So what's your take on screens before sleep?
Yeah, so certainly the experimental evidence done in labs like ours have put an iPad 30 centimetres from someone's face at full brightness and in a darkened room. There has been clear effects in terms of sleep, so they can demonstrate that it takes you longer to fall asleep. And if you put blue light blocking glasses on that, that effect can be minimised. Of course, when we are using iPads at home or TV or looking at our phones, that's not how we typically use them. And so I think probably for most of us, actually, the rest of our home environment is probably just as important. So are we sitting with bright white walls and fluorescent lighting on maximum light at nine o'clock at night? Or do we have it, like at sunset outside with warm lighting and nice and dim calm environment like you need to get ready for sleep? So, I think there's the effect of light from devices when iPads are used in the home is much smaller than what's been observed in the laboratory. Having said that, I still have my night mode on on my phone and, um, you know, I do try and minimise this personally because I think whatever I can do to help is probably good, but I think the home environment is probably more important. The other aspect with devices is what you're actually doing on the devices. So if you're watching nature documentary that you're not particularly interested in, you've got the blue light you know, turned down. That might not impact your sleep anywhere near as greatly as if you're playing a video game with your mates or if you're on social media. For teens, this is a big issue these days that if all of their high school friends are having a group chat, they don't want to say, "You know, look, it's nine o'clock. I need to, like, wind down for bed now." they want to hear what their friends have to say, and so this fear of missing out on the social interactions is actually a big driver of teens staying awake at night. So I think the light is one aspect. But then, you know, what you're doing on the device is probably as big a factor and your home environment.
So a little bit of passive consumption of screens probably isn't going to impact sleep as much as you know, a discussion or a social interaction that people are having via their screens.
Yeah, That's exactly right. And so, you know, my kids haven't got to the teenage years yet, but my plan when they have phones, et cetera, is to have an arrangement where, yes, they can use them up until an hour before their bedtime, for example, and then they can watch some TV after that, as long as it's not a thriller that's going to get their heart rate through the roof, but to have some compromise there that they can have it for a certain amount of time. But no phones in the bedroom, I think, will be what I plan to attempt to get them to stick to
We all have good plans.
Yeah, that's right. The reality might be a different story.
The other thing with kids these days is a lot Have these kind of LED lights in their room or fairy lights or coloured lights, either gamers or just for some decoration. Does that have an impact on their sleep? Should we say it has to be a certain tone of light? If they've got these fairy lights that are on, you know, while they're trying to sleep.
Yeah, it's a good question. I don't know that there's actually been that much research done on it. However, again, the blue light effect is real. And so my kids got bunks a few years ago and the oldest on the top bunk wanted a light so that she could read at night. So we put some strip lighting on there and I turned it on. I was like, "Oh, my goodness, what have I done? This is so bright." And so again, I was like, right, well, that's it. We'll just put some red cellophane over the top to make it a warm, calm, you know, think of sunset. That sort of is your evolutionary has been a good key to the- to the body that it's time to wind down and get ready for the restful part of the day.
And I think a lot of parents can kind of relate to uninterrupted sleep or wanting to maximise the sleep that their kids get, so I'm sure they're taking notes as I am. But in more serious scenarios, if someone is suffering from chronic pain, what can they look at from a sleep perspective to help them with that pain experience. Is it more than just, you know, monitoring their social media and putting some red lights in their room?
Yes, some of our research in healthy participants indicates that sleeping between six and nine hours is probably a good idea because some of our own research shows that even if you are not objectively experiencing any problems sleeping less than six hours, we still observe an effect on pain sensitivity, so you are less able to inhibit your pain.
Yes. I mean, I think the prioritising of sleep work with their doctor. If pain is causing them to have problems sleeping then pillows in appropriate place, if it's osteoarthritis and those sorts of things to make their bedroom as comfortable as they can, working out the timing of their medication. This needs to be done in consultation with their doctor. For example, opioids that commonly people might take do have depressant effects on breathing, and when you go to sleep, you already have a depression in your breathing. So, you certainly want to do that in consultation with your doctor, but trying to minimise your pain so that you can maximise your sleep is really important. And then I think the other thing that if you do have a bad night, try not to catastrophise about it. If you're awake at three o'clock in the morning, you know, you're uncomfortable. You're having difficulty sleeping. You know, to try and not immediately think, "Right, tomorrow is going to be a disaster." and get stressed about it, because then you're less likely to be able to go back to sleep. So this is where mindfulness can be really useful to sort of just accept what's happening. try not to be too disturbed by it as much as you can and relax. And maybe if you've got kids, Cassie, enjoy the silence of the house.
And that sounds like yeah, generally good advice, not just for people with chronic pain, but for those listeners who don't have chronic pain, I mean, what other things can you do to just improve your sleeping? Practically.
Yeah. So, I think one of the most important things that's often overlooked is keeping a fairly consistent routine. So if you try and go to bed about the same time, each night. Obviously, weekends, we often like to do social things and stay up a little bit. But try and get back to that within half an hour or so of whatever sleep time, you know, whatever bedtime you have. If you do that regularly, then your body is just primed for sleep. At that time. Your circadian rhythm, your internal body clock gets into a nice, strong rhythm. And so, even if you've had a bit of a bad day, your pain is a bit worse or whatever. You'll be more likely to be able to sleep. In terms of other things that are really important is to introduce a wind down time. And this comes back to what we were talking about with the screens as well. So, about an hour before bed, it's good to turn off the computer if you're an academic like us or to you know, shut down the social media if you're a teen and to again have that time to let your body relax and wind down and get ready for sleep. For younger kids, having a bath is really good. It actually works really well for adults, too, and there's probably an excellent solution for people with pain. So, when we have a warm bath or a hot shower, we actually we get quite warm. Our skin flushes a little bit. So, then you get out of the shower and your core body temperature actually falls. And that's a critical part of going to sleep. Our core body temperature drops, And so that's why having a bath helps. So that can be a good thing to incorporate, particularly for kids but into the wind down time. The other thing is just keeping an eye on your drive for sleep. So across the day, obviously, our drive for sleep builds up and up. If you have a nap at five o'clock in the afternoon, you're gonna reduce that drive a little bit. So at 10 or 11 o'clock when you go to bed, whatever your time is, you're not going to be as sleepy. So if you're going to have a nap, keep it short and keep it earlier in the day. And of course, you know, for people with pain again or people with young children like they can be absolutely critical to get those naps in order to function. But just be careful about when you do it. I guess. Other tips for sleep for everybody keep alcohol and, you know, low in the evening. Caffeine ideally, sort of not after, if you're sensitive, not after midday or one or two o'clock in the afternoon and then make sure your bedroom environment is appropriate for sleep. Dim lighting and about 20 degrees 22 degrees somewhere in that range is sort of optimal. Sometimes you can't control these things, but as much as you can. The saying that's common in the- in the sleep field is that the bedroom is for sleep and sex and everything else: TVs, devices, all of that, keep out of the bedroom so that you know you can really prioritise your sleep when you're in there.
So, Amy, when you go to a sleep conference, does this mean there's no drinking? Does this mean you sort of all leave at 8:30 to have your warm bath? Or, I mean, it's not what I heard at all it.
It's funny because I'm instantly brought back to the sleep conference in Adelaide last year where about three o'clock in the morning, most of the conference was in a bar dancing. So, um, I think that answers that question.
But that's just one day a year.
That's right.
Otherwise, you've got perfect sleep hygiene.
The rest of the time we're, sleep citizens.
Sleep citizens. And that's such great advice, not the dancing on the bar part. But the stuff you said before that is all great advice. But I guess is it also true to say that quote unquote "normal" sleep varies a lot from person to person, and I think there's a lot of anxiety around people getting the perfect sleep. There's a lot of focus on sleep in the health and wellness space at the moment. I think just some perspective taking in, you know, if you can't have exactly the same routine or exactly the right wind down or things happen, just some advice for people, but not to get too hung up on the perfect sleep. Even if that exists.
Yeah, I think you're absolutely right, Cassie. Even in, you know, when we have perfect opportunity for sleep, people are vastly different. Some people, six hours, that's it. They spring out of bed, you know, like they had 10 hours for me. And so there is-there is individual differences in how much sleep we need, how deeply we sleep when we are asleep. That changes over age, of course as well. And so, again, I think if you're not falling asleep, you know, excessively during the daytim,e you're managing, then try not to get too hung up on it. But then you know when you can- you get back to prioritising it. And in a few years, your children won't want to be in bed with you anymore. And you'll have plenty of opportunity to practise good sleeping.
It's such good advice that I am going to make my kids listen to this episode.
Well, just make sure it's not before bedtime.
Thanks so much for talking to us today. Amy and Natalia.
Thank you for having us.
You've been listening to psych talks with me, Nick Haslam and Cassie Hayward. We'd like to thank our guests for today. Professor Amy Jordan and associate professor Natalia Brumley. This episode was produced by Carly Godden with production assistance from Mairead Murray and Gemma Papprill. Our sound engineer was Jack Palmer. Thanks for tuning in, and we'll be back in a fortnight with another great episode. Bye for now.
