July 28, 2023

expert reaction to study looking at napping times and children’s brain development

A study published in JCPP Advances looks at napping frequency and cognitive development in children during the COVID-19 pandemic.

Prof Russell Foster, Professor of Circadian Neuroscience, University of Oxford, said:

“The authors of this study conclude that napping during the day is associated with a slower development of cognitive skills and vocabulary. This is an interesting finding, but there could be an alternative interpretation. The need to nap during the day could indicate poorer night-time sleep. Night-time sleep is a key time for memory consolidation and problem-solving. Indeed, poor sleep at night in adults is strongly correlated with reduced cognition and the formation of memory. So, increased day-time napping might just provide a measure of poor night-time sleep, which in turn, leads to reduced cognition and memory consolidation.  It is not the increased day-time napping per se that is causing the reduced cognition, but the reduced sleep at night. It would be interesting to obtain more detailed measures of sleep and sleep structure in future studies.”

Prof Alastair Sutcliffe, Professor of General Paediatrics, University College London (UCL), said:

Does the press release accurately reflect the science?

“There are some methodological omissions in the press release. The press release fails to state the way the children were engaged in the study. This is very important for purposes of scientific conclusions as it would suggest a ‘convenience sample’ or a ‘biased sample’ etc.”

Is this good quality research? 

“Moderate quality.”

Are the conclusions backed up by solid data? 

“Allowing for various biases yes (see below for more information).”

How does this work fit with the existing evidence?  

“It fits well, noting that no one knows why we need sleep which is a need across all animals.”

Have the authors accounted for confounders? 

“Not fully (see below for more information).”

Are there important limitations to be aware of?  

“This was a convenience sample from social and professional networks, not a proper random cohort, thus participation bias is likely to be a significant factor in the validity or not thereof.”

What are the implications in the real world? 

“Little and often (in other words little ones need frequent naps when they get tired.).”

Is there any overspeculation? 

“No.”

“This is an interesting paper that studied a group of preschool children during lockdown. The recruitment method was via a social sample not a truly scientific method of sampling.  And correctly in this paper, the method is described as a survey. The paper claims that the study was approved by xxx ethics committee which does not exist and implies a typo or other error.

“Participation bias is inevitable and also the participants were given an inconvenience gift voucher too. Notwithstanding this, the findings are of interest and tend towards the conclusion that letting preschool children nap as little or as much as they need is a good thing. And possibly that children who nap more need more time to consolidate their learning. And maybe this is a harbinger of a lower IQ. However, it is very important to be aware when reporting on this paper of the very powerful evidence that children from less privileged backgrounds do academically better if they get a ‘surestart’ as per the eponymous programme started by the Blair government. In a high-quality study of children’s language acquisition, it was shown that a typical toddler is exposed by around 3 years of age to 2,000,000 words (not different words) but in a socially deprived environment, only 800,000 and a lot of those were deemed to be critical. So any study which infers as per this study that, as it alleges children in nursery get less sleep than at home, (contrary to my own observations) needs to be carefully reported as particularly for some children nursery is a GOOD thing. Nobody knows the true function of sleep, but it is a universal need.”

Professor Helen Ball, Professor in the Department of Anthropology, and Director of the Durham Infancy & Sleep Centre, University of Durham, said:

Does the press release accurately reflect the science?

“Yes, it seems to.”

Is this good quality research?  Are the conclusions backed up by solid data?

“Yes, but perhaps not as solid as they think!”

How does this work fit with the existing evidence?

“They do a good job of summarising this within the paper.”

Have the authors accounted for confounders? 

“They have examined a number of confounders, however, they make an assumption that is unexamined in the paper – that the sleep environment for these children at home during lockdown would be more conducive to day-time napping than the day-care environment – however for some families, the home environment may also have disturbed day-time napping if multiple siblings were simultaneously off school with TVs, video games and other noisy activities taking place. In day-care settings, nap-times are generally quiet time when all activity quietens down, but in the home it is likely that older siblings (and even parents being off work unexpectedly) will disturb a youngster’s day-time napping behaviour. So, the premise on which the benefit of studying children during lockdown on which the paper is founded may be dodgy! So, a confounder that is not considered is number of other children in the home and/or crowding in the home. Also, the nap duration data were reported by parents which is subjective and prone to mis-estimation.”

What are the implications in the real world?  Is there any overspeculation?

“They are challenging previous conclusions drawn about the effects of napping, which is good.”

Could you clarify more on what conclusions we can draw from this research? I.e., Is this research suggesting we should get children to nap less to improve their brain development, or that they observed some children are more efficient at consolidating information during sleep, so they nap less frequently, and vice versa?

“The latter I think – but it is possible the short nappers were being disturbed, so without looking at the density of people/siblings in the home during the study I don’t think we can say whether this study is an improvement on the previous ones (unless I missed the fact that they only recruited first-born children!).”

‘More frequent naps are associated with lower cognitive development in a cohort of 8 to 38-month-old children, during the Covid-19 pandemic’ by Teodora Gliga et al. wa published in JCPP Advances at 00:01 UK time Friday 28 July 2023, which is also when the embargo will lift.

Declared interests

Prof Alastair Sutcliffe: “I have no conflict of interest with this report.”

Prof Helen Ball: “I have no conflicts of interest regarding this paper or research team.”

For all other experts, no reply to our request for DOIs was received.