In this Papers Podcast, Dr. Isabel Morales-Muñoz discusses her JCPP paper ‘Shorter night-time sleep duration and later sleep timing from infancy to adolescence’ (https://doi.org/10.1111/jcpp.14004).
There is an overview of the paper, methodology, key findings, and implications for practice.
Discussion points include:
- Definition of poor sleep health and what the hallmarks are of poor sleep health.
- The typical trajectory for sleep duration and sleep timing from 6 months to 16 years of age.
- Persistent shorter sleep and the impact of later chronotype on adverse outcomes.
- The association between family adversity, as well as lower maternal socioeconomic status during pregnancy, and poor sleep health from infancy to adolescence.
- Implications for clinicians and CAMH professionals in terms of how patients are screened as well as in terms of treatments and interventions.
- Recommendations for policymakers.
In this series, we speak to authors of papers published in one of ACAMH’s three journals. These are The Journal of Child Psychology and Psychiatry (JCPP); The Child and Adolescent Mental Health (CAMH) journal; and JCPP Advances.
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I am Assistant Professor in Psychology, based at the Institute for Mental Health, School of Psychology, at the University of Birmingham. Originally from the Basque Country in Spain, I have conducted my research in different countries including Spain, USA, Finland and the UK. Since my PhD, my main research has focused on understanding mental health problems in young people, and ways to improve mental health. Currently, I focus more specifically on understanding sleep problems in children and young people and how sleep problems can be a risk factor for developing mental health problems.
Transcript
[00:00:10.018] Jo Carlowe: Hello, welcome to the Papers Podcast series for the Association for Child and Adolescent Mental Health, or ACAMH for short. I’m Jo Carlowe, a Freelance Journalist with a specialism in psychology. In this series, we speak to authors of papers published in one of ACAMH’s three journals. These are the Journal of Child Psychology and Psychiatry, commonly known as JCPP, the Child and Adolescent Mental Health, known as CAMH, and JCPP Advances.
Today, I’m interviewing Dr. Isabel Morales, Assistant Professor in Psychology, based at the Institute for Mental Health, School of Psychology, University of Birmingham. Isabel is an author of the JCPP paper, “Shorter Night-time Sleep Duration and Later Sleep Timing from Infancy to Adolescence.” This paper will be the focus of today’s podcast. If you’re a fan of our Papers Podcast series, please subscribe on your preferred streaming platform, let us know how we did, with a rating or review, and do share with friends and colleagues.
Isabel, thank you for joining me. Welcome. Can you start with an introduction about who you are and what you do?
[00:01:14.453] Dr. Isabel Morales-Muñoz: Yes. So, thank you very much, Jo, for a very kind introduction. So, as you mentioned, I’m Assistant Professor at the Institute for Mental Health, that is part of the School of Psychology at the University of Birmingham. And so, my main research is actually focused in sleep and how sleep relates to mental health problems. More specifically, it’s trying to understand whether sleep problems happening in early stages of life, whether that can constitute at least factor for developing mental health problems in the future stages of life.
[00:01:51.068] Jo Carlowe: Thank you. So, today, we are going to look at your paper, “Shorter Night-time Sleep Duration and Later Sleep Timing from Infancy to Adolescence,” recently published in the JCPP. Before we go into the detail of the paper, Isabel, can you define “poor sleep health”? What are the hallmarks of poor sleep health?
[00:02:09.973] Dr. Isabel Morales-Muñoz: First, to clarify, so in this specific study, so actually, we used the term of “poor sleep health,” kind of, an equivalent to what it could be sleep problems. But the specific concern that we had in this study is that, actually, we were not able to categorise these as sleep problems, as actually, there was not a specific measure within the questionnaire that asks the parents or the children whether, actually, this constitute a problem per se. And that is where, actually, we decided to use the term ‘poor sleep health’.
So, this is a term that was defined some years ago by Professor Daniel Buysse, that he is one of the most renowned experts in the field of sleep. And so, this term, ‘sleep health’, is defined as “a multidimensional pattern of sleep-wakefulness, adapted to individual, social and environmental demands, that promotes physical and mental wellbeing.” It could be similar to concept of sleep quality, but emphasising that this actually has an impact on the health and wellbeing of the individual.
In our specific case, so it’s referring to these specific sleep health dimensions, of sleep duration and sleep timing, which are aspects of these wider sleep health or sleep patterns, insofar that it is down to the sleep quality or part of the time, insomnia symptoms, yeah.
[00:03:49.028] Jo Carlowe: Great, thank you. Your paper detects trajectories of “persistent poor sleep health.” Can you tell us what is a typical trajectory for sleep duration and sleep timing from six months to 16-years-of-age?
[00:04:03.173] Dr. Isabel Morales-Muñoz: Yeah. So, actually, this is a very good question. It is not that I can give any straight. Actually, the sleep patterns are – of a specific group actually will depend on the specific population that you are measuring that. Also, it might be fair, depending in which specific country, or even sometimes depending on the specific season. So, taking into consideration these pictures, actually, what we present in this study is the trajectories, and in that sense, so it’s true that we detected a specific trajectory that refers more to these normative patterns.
But actually, this refers to the specific large population sample that were recruited in the UK, but in a specific area, which was the Avon area, within the 90s age range. So, also, like – ‘cause we know that actually, a sleep duration is something that is becoming shorter over the years and also, children, because of the societal demands, we know that children and anyways, like, all of us, we tend to go more and more often, later to bed. So, yes, taking into consideration the location and a specific year that this data was collected. So, then, this through that anyways, we were able to detect some normative patterns within that very large sample size. It is quite representative to considering those restrictions.
So, what we saw in terms of the sleep duration, so what we could consider is a normative pattern, is that at the age of six months, so the amount of time that the sleep – that the children sleep at night is around an average of ten hours. Then, this increase to ten hours and a half to 11 hours from the age of 18 months to seven-years-old. And then, we start decreasing the amount of hours of sleep slowly from the age of nine to 11-years. So, this decrease over one hour, so in our data we have that between the ages of nine to 11-years-old, the children tend to sleep around ten hours at night. And then, it is true that we saw a considerably decrease of the sleep duration at the age of 15-years-old, in our data, which anyways, this is consistent with what we know in terms of the sleep duration in adolescence. So, within our data, so a normative pattern of sleep duration was around eight hours and a half.
And then, in terms of the sleep timing, so sleep timing refers, usually, to the time that the child goes to sleep. And so, in that sense, we found that in average, so the normative trajectory, it was that from the age of six months to six years it was around 8:00pm, at the of 15-years-old we found in our data that the average is around 11:00pm.
[00:07:10.520] Jo Carlowe: Excellent. So, let’s get into the details of the paper itself. Can you start with an overview? What did you look at and why?
[00:07:20.093] Dr. Isabel Morales-Muñoz: So, in this study, what we explored were the trajectories of night-time sleep duration and also, the sleep timing. The sleep timing in this case was measured with two specific variables. One was the bedtime and the other one, it was a measure that we created that is called the “midpoint of night-time sleep.” So, it’s similar to bedtime and actually, midpoint of this – or midpoint of night-time sleep is a measure that is used to indirectly study the chronotype. So, the chronotype, it is, like, the preferred time of the individual, for example, that they may go to sleep or that they may be more active for a specific task.
So, we use midpoint of sleep as an indirect measure of chronotype, which actually, the midpoint of sleep is the clock time between the sleep onset, but also, the wakeup time. Sometimes bedtime also is used as an indirect measure of chronotype. But if you don’t take into consideration what time the child goes to a sleep, so then, actually, we are not actually exploring whether this might have a clear impact in that sense. So, the midpoint of a sleep, it is more accurate measure of chronotype. Yes, sorry, so in that sense, what we explore were these three main trajectories. So, one trajectory of night-time sleep duration, a trajectory of bedtime and separately, another trajectory of midpoint of a sleep.
So, we had data from children since the age of six months, until the age of 15-years-old. So, actually, there is, so far, not any study that we think that in the UK, actually, explores in detail these specific trajectories. Sleep duration is a bit more studies that try to explore that, but also considering the important factor of the chronotypes. So, also, how the chronotype develops from infancy to adolescence.
And I guess one other focus that we were very interested in this study, so we were, of course, exploring the different trajectories, but we had a very clear focus. We were interested in those specific trajectories that detect those individuals that present persistent or chronic sleep problems. So, we know a sleep is something that develops and there is a lot of variability in terms of the sleep, because childhood, there might be children that may sleep poorly at the age of six months, but then, they might improve their sleep and then, at the age of one-year-old, they might be considered good sleepers, right? So, then, what we were actually interested is what happens in those children that present sleep problems persistently since infancy to adolescence, based on our hypotheses that actually, these are the children that are at highest risk of a number of adverse outcomes?
[00:10:19.828] Jo Carlowe: I want to look at the findings in a moment, but before we do that, can you say a little bit more about the methodology that you used?
[00:10:27.608] Dr. Isabel Morales-Muñoz: Yes. This study is what we call a secondary data analysis study. So, we did not conduct our own data, but we use an existing dataset from the UK. So, this is a very widely used and validated longitudinal cohort study. So, this is the ALSPAC cohort, also known as the “Children of the 90s,” that refers to Avon Longitudinal Study of Pregnancy and Childhood. As I mentioned earlier, this was a study conducted – started in the 90s. Recruited around 14,000 women during pregnancy. They have been followed up since the 90s, so the parents and the children, until currently. So, now, those children, they are around 30-years-old and actually, now there is the children of the children. So, there are people that continue involved in these studies. So, it’s an amazing resource that continues growing.
For this specific study, so we selected those sleep variables that were from six months until the age of 11-years-old, and then, at the age of 15-years-old, the information that we had was self-reported by the adolescent in that case. The variables that we used was night-time sleep duration, bedtimes and then, we created variable of midpoint of the sleep. And in addition to that, we were interested detecting trajectories of sleep. So, the second part of the study was actually to detect whether a – there are any key relevant early life risk factors that happened before the age of six months that would lead to the development of persistent sleep health conditions over time, right? So, in that sense, specifically with the data, right, it will be whether there are specific early life risk factors for persistent shorter sleep, or whether early life risk factors for persistent later bedtime or for persistent later midpoint of the sleep? These are the three trajectories that we would consider that this is the poorer sleep health, as we call it in this paper.
So, in terms of the early life risk factors, so we selected a range of pregnancy or very early life potential risk factors, which were the sex of the child, ethnicity, birth weight, gestational age, health and temperament, all about the child. And also, some risk factors from the mother, such as mother’s adversity factors happening during pregnancy, age of mother at the birth of the child, socioeconomical status of mother and also, postnatal anxiety and depression. These factors were chosen based on existing evidence that these are actually relevant factors for sleep problems.
[00:13:28.428] Jo Carlowe: Isabel, what key findings from the paper would you like to highlight?
[00:13:32.893] Dr. Isabel Morales-Muñoz: We were able to detect different trajectories of a sleep duration, and also bedtime and midpoint of sleep, over time. So, I’m highlighting that this is a key finding, because sometimes, when we use data about the sleep, considering that a sleep is so variable between subject, but also within the same subject, sometimes it is not possible to actually detect the specific trajectories, relevant groups of children over time, because we are trying to categorise the groups from infancy. So, considering very large timeframe, so from infancy to adolescence. So, actually, that was, kind of, one key finding that actually, we were able to detect those trajectories as happening. And importantly, so we were able to detect, although a small – but a small, I think, is what is representative of this – of the general population. So, we were able to take a small group of children that actually present with persistent sleep problems in infancy to adolescence. So, that was, kind of, one of the main key findings.
And the second key finding is that, so, when we test the associations between the early life risk factors and the three main domains of poor sleep health, we found that there were different early life risk factors that were associated depending on the outcome. But overall, actually, we found that there were two main risk factors that were associated with the three main sleep domains. So, these were early life family adversity. So, basically, this refers to adversity conditions of the mum during pregnancy, and also, lower maternal socioeconomic status. So, those two, which we know this refers to adversities and to poor conditions of the life environment of the child, in that sense, these actually were the most relevant risk factors for developing persistent poor sleep in childhood.
[00:15:41.868] Jo Carlowe: I want to return to that in a moment, around the adversity and low socioeconomic status of the mother, but I want to, sort of, drill in a bit onto persistent shorter sleep and also, the impact of later chronotype. So, your paper states that “Persistent shorter sleep potentially constitutes to the group at highest risk of developing adverse outcomes.” Can you elaborate on how and why this is?
[00:16:08.293] Dr. Isabel Morales-Muñoz: So, I mean, of course, we’ve per – this is something that, still, we need further understanding of this, but I can just provide some explanation space on what we know already. So, one of the potential explanation is because actually, there is a cumulative effect of the poorer sleep that is happening. So, if it’s only happening at specific stage, but then there is good sleep at the other stage, so, actually, in that sense, it can be restorative, then it might have a less severe impact. But if we are considering that in these cases, so a child with persistent poorer sleep, it means that at all the different stages, so there is no rest in that sense of the effect that the poorer sleep is having, especially in the impact on the brain, which is something that we need to explore further.
But one of the hypothesis behind is so, the brain is – of course, like, childhood and adolescent are critical stages for the brain development and we know that a sleep has an impact in the brain development, especially at these critical stages. So, if there is consistent poorer sleep, consecutive, and a cumulative impact on the brain, that consequently, this will put itself at highest risk of wide range of aspects. Such as in my research, I focus in how this could link to mental health problems.
Actually, this is supported by some of our research that we have been done in parallel. So, we have found that, actually, persistent shorter sleep in children is a risk factor for developing psychosis in young adulthood, while there is not that much evidence that a sleep at specific stages is a risk factor in that sense, is the poorer sleep.
And finally, I guess to highlight that this actually mimics the experimental designs that there have been for many years in terms of the sleep deprivation is a well-known paradigm to induce psychotic symptoms. There are many studies that in order to test the causality of a sleep, so they’re in evidence suggesting that depriving sleep in healthy individuals for two or three consecutive days actually leads to the development of psychotic symptoms in these healthy individuals, compared to those that do not experience these sleep deprivation conditions.
[00:18:33.868] Jo Carlowe: So, I have a similar question around later chronotype, because previous studies suggest later chronotype is associated with reduced school performance, increased mental health problems and sleep problems. What is it about later chronotype that puts children at greater risk?
[00:18:51.853] Dr. Isabel Morales-Muñoz: Again, so this is a great question. The thing with chronotype, we know quite little compared to a sleep duration, for example, especially in childhood. So, this, again, I need just to highlight that we need further understanding of what the role of chronotype is, especially in younger population. We feel when people start talking about their sleep problems, we tend to forget, also, about the chronotype, circadian rhythms and they are quite highly related to each other. That’s what, actually, we do not have, I guess, much evidence of the mechanisms why these were linked. But having said that, one of the main explanations here, it could be some people are with an actually late chronotype, per se, compared to an earlier chronotype, it might not be a good or bad thing.
I guess the problem that we find currently is the society that we are living in and so, basically, what happens with the children is that they might have born with the late chronotype on things that we just cannot change. There are some therapies, but still, I guess the debate is there, right, whether it has to be changed or not. But I guess it’s the thing is like, the child is born in a society that you need to wake up at the specific times, especially during schooldays, so, every child needs to wake up at the same time. And currently, we are tending, in the society, to wake up earlier and earlier because the society has higher demands, right?
So, then, actually, with this kind of simple explanation, already we could see that a child has a later chronotype, that if you have a later chronotype, you are going to bed later. Otherwise, you are not going to fall asleep, or you are going, I want to say, have insomnia symptoms because I don’t fall asleep at certain time, well, yeah, because your chronotype is later and maybe this is not the time for you to go to sleep. But then, if they may go to sleep, for instance, one hour later than a person that has an earlier chronotype, then both of them, probably they will wake up at the same time because this is established not by your internal clock, that usually the person that is later chronotype also wakes up later. So, then the sleep needs them to be quite similar between each other. So, in that sense, those with later chronotype, have later bedtime, but wake up at the same time. What happens? They have shorter sleep duration.
[00:21:13.668] Jo Carlowe: Right. So, is it possible that the increased mental health problems that are associated with later chronotype might not exist if adolescents were allowed to get up at their individual preference and go to sleep at times that suits them?
[00:21:27.021] Dr. Isabel Morales-Muñoz: That’s something that there is one idea behind that. I think there have been, actually, several initiatives. I think maybe you’re aware about this delaying the school start times which these ideas behind that. But, of course, we understand that this is not possible for the society as a whole, because then, the parents will be complaining. So, it is quite a complicated…
[00:21:46.377] Jo Carlowe: It’s very complicated.
[00:21:46.377] Dr. Isabel Morales-Muñoz: …reality.
[00:21:47.388] Jo Carlowe: I want to turn to the finding that you highlighted earlier. So, this is that family adversity and lower maternal socioeconomic status during pregnancy were associated with poor sleep health from infancy to adolescence. Can you elaborate on why this might be?
[00:22:05.413] Dr. Isabel Morales-Muñoz: So, the Family Adversities Index that we used in the ALSPAC, actually, it covers wide range of conditions that we know that affects the life in that sense of the mum during pregnancy, around things like poor housing conditions, poverty, against problem with economic difficulties, that relate, of course, to socioeconomic status. So, I guess a very wide range of adversities, like childhood adversities, that we know to have an impact. And so, I guess in that sense of both insofar family adversities and lower socioeconomic status, this refers to the poor environmental conditions that we know that, actually, there is, kind of, more and more evidence suggesting that actually, this has an impact in our health, but also, this has an impact in the sleep of the child.
So, it is, I guess, quite complex in that sense, the system, but we know with, you know, children from poorer socioeconomic backgrounds are at highest risk of a wide range of health outcomes. This is related, so in that sense, those from lower socioeconomic status are going to experience more sleep problems, but also, those that are suffering from a wide range of early life adversities.
[00:23:24.784] Jo Carlowe: And what are the implications of your findings for Clinicians and CAMH professionals in terms of how patients are screened and in terms of treatments or interventions?
[00:23:36.533] Dr. Isabel Morales-Muñoz: The measures that Clinicians and other practitioners are working with children, so for example, Social Workers, they, so, for example, consider routinely screening for adverse childhood experiences, including also, of course, socioeconomic status. So, I guess within those routinely collected measures, they should – there should be, like, progress measures of socioeconomic status within their daily practice. And also, to widely considerate a wide range of potential early life adversities that would be detecting those children that might be at highest risk of poor mental health outcomes, because they are so highly linked to each other.
[00:24:19.908] Jo Carlowe: Given the association between family adversities, social economic status and poor sleep that you mentioned before, what recommendations emerged from your research for policymakers?
[00:24:31.069] Dr. Isabel Morales-Muñoz: So, actually, our results highlight the necessity to address inequalities in the health of infants in the UK. So, we know that there are, kind of like, clear disadvantages in terms of the environment of where the child is born, and also, in terms of the socioeconomic status. We know this has major impact in their life. So, addressing these health inequalities is key and also, this follows some of the recently published recommendations by the Royal College of Paediatrics and Child Health that highlight the necessity of reducing health inequalities as a result of child poverty and adverse childhood experience.
[00:25:15.668] Jo Carlowe: Are you planning any follow-up research, or is there anything else in the pipeline that you would like to share with us?
[00:25:21.373] Dr. Isabel Morales-Muñoz: We are really interested in the – a specific group of our children that present persistent poor health, especially using this specific dataset of the ALSPAC. So, currently, we are focusing in follow-up studies, where we are trying to understand or explore the specific impact of these poor sleep health trajectories in the development of mental health outcomes. So, as I mentioned earlier, so we recently published a study where we found that the persistent shorter sleep duration is a risk factor for psychosis in young people and also, we want to explore that, similarly, whether this has an impact in the development of mood disorders, for example, such as depression or anxiety.
And also, not only to consider all this shorter sleep duration, but also to explore the impact of persistent late chronotype, I guess to further understand, as we were saying earlier, right, whether actually that has an impact or not, or whether – what is the mechanism? ‘Cause maybe we try to see whether the sleep duration has an impact there. We could actually try to understand a bit more. But yeah, now we’re trying to understand the specific impact of these sleep trajectories in the long-term in these individuals.
[00:26:41.828] Jo Carlowe: Sounds really interesting. Isabel, finally, what is your take home message for our listeners?
[00:26:47.733] Dr. Isabel Morales-Muñoz: So, the first one is, like, it is very important to assess and further understand sleep and then, also, I guess, sometimes when I explain my research, many people and everybody gets sometimes afraid. Say, you know, “Then the risk” – they have a specific. But I think all of us at certain stages of our life, we have experienced sleep problems. So, that’s something that, anyway, so, sleep problems at specific stages, for different circumstances, is something that it happens, it’s normal and that’s not necessary needs to have a direct impact in our daily life or in our future.
But I guess what is important, what I wanted to highlight in this research, is that actually is to detect those children that actually present with this persistent poorer sleep over time. ‘Cause I guess all of us sometimes will have heard the sentence of somebody saying, “Oh, yeah, for all my life I’ve been sleeping poorly,” and we just assume that by default, it’s, like, a trait of ourselves. But in those cases, it might be, well, I guess maybe that is something maybe we might not need to consider as okay, it’s part of myself, but maybe something that actually if you could do something to improve, maybe you might feel better, ‘cause then those people might start then considering things. “Yeah, I tend to always,” kind of, “to get ill more frequently. I tend to get, you know – I, kind of, have more depressive symptoms.” Sometimes I will try to understand, okay, maybe the reason is behind something else.
So, I guess it’s actually, you know, not to get alarmed by the fact that sometimes we all can have, like, poorer sleep for different reasons, or for children, you know, there are developmental stages. But I guess it’s just to pay special attention in those casings – those cases, sorry, that we see that the – their sleep problems persist over a consecutive period of time.
And then, the second take home message is to highlight that are – there are a wide range of early life risk factors that actually can also lead to the development of sleep problems. So, the same, it is not that sometimes we assume, “Oh, I was born like this, I just sleep poorly.” And then, most of the cases actually there are specific reasons behind why those sleep problems are happening. And in many cases, those are factors that can be – so, I guess the positive message here is that sleep is something we can modify and there are a wide range of the sleep interventions, that they work. It’s much easier to modify, in that sense, that other more complicated behaviours or health-related aspects, and also, not only sleep, but factors that affect the sleep. Sometimes it can be the light, it can be the temperature. Sometimes there’s specific factors that also are easier to modify can have an impact in sleep. So, I guess it’s trying, also, to be really positive messaging in that aspect.
[00:29:44.308] Jo Carlowe: Brilliant. Thank you ever so much. For more details on Dr. Isabel Morales, please visit the ACAMH website, www.acamh.org, and Twitter @ACAMH. ACAMH is spelt A-C-A-M-H, and don’t forget to follow us on your preferred streaming platform, let us know if you enjoy the podcast, with a rating or review, and do share with friends and colleagues.
