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Aug 22, 2019

In Episode 9 of the DIAL Podcast, Nirosha Varghese from Bocconi University discusses her research looking at the links between early childhood sleep and how children get on at school later on.

Further information:

Early childhood sleep and later cognitive human capital is Marie Curie funded research analysing the relationship between early sleep problems and later cognitive outcomes in a life course perspective. It was presented at the DIAL Mid-Term Conference in June 2019.


Nirosha Varghese: Sleep tight! Does a baby’s sleep matter for how they get on at school later on?

In Episode 9 of the DIAL Podcast, Nirosha Varghese from Bocconi University discusses her research looking at the links between early childhood sleep and how children get on at school later on.

Further information:

Early childhood sleep and later cognitive human capital is Marie Curie funded research analysing the relationship between early sleep problems and later cognitive outcomes in a life course perspective. It was presented at the DIAL Mid-Term Conference in June 2019.

Christine Garrington  0:00 

Welcome to DIAL, a podcast where we tune in to evidence on inequality over the life course. In today's episode we're talking about children and sleep and asking if sleep problems in very young children might negatively affect how they get on in reading, writing and maths later on. Our guest is Nirosha Varghese from Bocconi University, who started by explaining the background to her research. 

Nirosha Varghese 0: 26  

So, we know that previous studies show that what happens in early life has consequences for later on. But then all the studies that have looked into it usually looks at factors like parent and ACS income, or like exogenous shocks like the recession or war, or earthquake, but none of these studies has looked at sleep as a shock. So, what we're trying to do here is taking evidence from medical literature, which shows that there are adverse effects of sleep problems on cognition and trying to study it from a life course perspective and moreover, although there are some studies that are done in the US, but it has not been done in a European context, and also not from a life course perspective

Christine Garrington  1:08 

So, tell us a bit about where you got your information from or where you are getting your information from.

Nirosha Varghese 1:14 

So, this information comes from ALSPAC, which is the Avon Longitudinal Study of Parents and Children. It's also known as the ‘Children of 90s data’, because it's a cohort for children born in the 90s, so they initially selected pregnant women who were supposed to give birth in a period of one year, one to one and a half years, and that's where the data comes from. It's geographically limited to Avon and because of this we have a very rich data set. So, we have information on pre-natal characteristics which is really important. The sample is 14,500 approximately. 

Christine Garrington  1:48

So, a really big useful data set, but what sorts of things were the mothers asked about in ALSPAC that helped you examine these questions about sleep and how children get on as they get older?

Nirosha Varghese 1:59 

So first of all, we have sleep measures and here, they're using sleep subjective sleep measures not objective. So here they asked if the children continuously woke up every few hours during the sleep. So, we use that and we use a very similar measure which is like the children wake up during the night. So this is measured all the way from 18 months, like 1.5 years, until 7.5 years. So we have seven points in time. We also have measures on cognition, including IQ, short term memory, some measures for math and English standardised scores and so on. We also have measures on non-cognition, which is coming from standard difficulties questionnaire on behavioural difficulties, social fears and so on. And most importantly we can control for a lot, a lot of covariates including prenatal characteristics and socioeconomic characteristics. 

Christine Garrington  2:55

So, what have you done with all of this fantastic information?

Nirosha Varghese 2:58 

So first of all, we looked at the relationship between different patterns of childhood exposure to sleep and its effects on cognition. So, already we know that there's a negative effect, but we want to know if the timing of that sleep problem actually makes a difference. So, it could be that a sleep problem at 1.5 years is all that matters and sleep problems at five years doesn't matter. So, if you actually do an intervention at five years, it doesn't make sense. So, this is what we are doing, because we have a longitudinal data, we test for different kinds of models. Once we know which model fits the data better we try to see if there are some scarring effects of sleep. So, this past sleep matters, even when controlling for the current status of sleep problem and we also try to understand some of the mechanisms underlying this relationship. 

Christine Garrington  3:49

Yes, so what’s going on behind the scenes, yes indeed. So from what you've found so far does when a child is experiencing sleep problems as you said, the timing of this, matter, and if so, how does it matter?

Nirosha Varghese 4:01 

So, what we find it that it’s not per se the timing that matters. It is the duration of exposure. So, the longer you're exposed to sleep problems, the larger the effect on cognition. So, what this means is that this is very similar to what Heckman in his work says that the earlier the investment the better, so if you do the intervention when the child is young, because then you can shape the child's skills or problems much more better. Better in terms of cost and in terms of the effects that you want. Since there's a link between infant’s sleep and childhood sleep, it's better to do the intervention earlier on, so that's what we find.

Christine Garrington  4:39

Indeed. Now whether one thing causes another directly is always a bit of a tricky area to claim, but what are you able to say so far would you say?

Nirosha Varghese 4:48

So, we cannot establish causality, but what we can say is that there is a negative effect, negative association and this actually, we see that it's a cumulative effect. We also see that there is a scarring that suggests that early intervention is better.

Christine Garrington  5:03

Tell us a bit more about that scarring effect and first perhaps explain by scarring effect, what do we mean and what did you find when you looked at it?

Nirosha Varghese 5:13

So scarring effect is usually used in unemployment and well-being literature. So, what it says is that even when you control for current employment status, so even if you're employed at the moment, past unemployment can actually have scarring effects on a well-being. So, we adapted it into this literature so what we see is that, even if it's you sleep now, can past sleep problems have an impact on cognition? What we find is that even if you sleep well now or whatever your status of sleep is, past exposure to sleep problems, the duration, higher the duration, worsens the effect on cognition. 

Christine Garrington  5:47

What do we learn from your findings would you say so far and how can the research that you've done help those of us who are key whether it's parents or policymakers, teachers all of those interested in the well-being of children help ensure that they get the best possible start in life because that's what we're aiming for really isn’t it? 

Nirosha Varghese 6:05

So, I think the main takeaway is, when to do the intervention and what we find is exactly resonating with that. So, both the evidence on cumulative sleep problems, and on scarring effects calls for early intervention. So, it could be either in terms of healthy sleep behaviours when you’re young like no screen  time after you go to bed, or going to bed at the right time, sleeping proper amount of time. If children are taught how to do it properly, then this can be like lifelong habits, and there are also sleep clinics, so if infants have problems in sleeping, then it's better to take them to the clinics where they're taught how to sleep better. Also, the fact that behavioural difficulties in childhood is coming from sleep problems, it could be one of the channels. Since these problems also happened in the childhood and these are also malleable, as in you can shape them, this also shows that there is a scope for intervention during mid-childhood, as well as for behavioural difficulties.

Christine Garrington  7:05

So, the simple message is getting there really early with your children, get them into good habits, sleep is really important in the longer term. If you’re struggling get help presumably as well. So where does your research go from here then? 

Nirosha Varghese 7:20

So, the next step is to establish causality. So, causality in terms of the relationship between sleep, accumulative acts of sleep on cognition and also the causality between infants’ sleep to mid-childhood sleep. So once we know that there is a causality between early sleep to late sleep then we know that we probably have to do the intervention earlier on for sure. 

Christine Garrington  7:42

`Early childhood sleep and later cognitive human capital is Marie Curie funded research presented at the DIAL mid-term conference in June 2019 by Nirosha Varghese. You can find out more about the NORFACE funded DIAL projects at Thanks for listening to this episode of our podcast, which is presented and produced by Chris Garrington and edited by Elina Kilpi-Jakonen.