Why won’t my toddler sleep? Audio lay Summary

Medicine and Health Sciences: Paediatrics, Perinatology and Child Health

Download lay summary:


Why won’t my toddler sleep at night?!

Anyone who is a parent, or knows a parent with young children, will have heard that babies and toddlers are not always great sleepers. In the first few years of life, nap and sleep patterns change dramatically and many youngsters wake repeatedly during the night-time. It is only when the child reaches around the age of 5 when more adult-like sleeping patterns are established (so fewer or no naps, more solid night-time sleep). There is some scientific evidence out there suggesting that sleep arrangements, such as the common practice of co-sleeping (particularly in the Non-Western world) can play a role in interrupting sleep for both mother and child. We have learned that sleep is important for small children to aid their development and learning. There are loads of studies that have tried finding out what sleep arrangements are best, but none have been conclusive so far…

This study by Machiko Nakagawa and colleagues back in 2021 specifically looked at whether bed-sharing, co-sleeping and night-time breastfeeding have a negative effect on night-time sleep.

How did they do it?

They recruited 106 one and half year-old children (and their parents) to the study. They recorded activity and sleep using ‘actigraphy’ (so, imagine a miniature wristwatch-like accelerometer, which continuously records movement for an extended period, for the children it was attached to the waist because that was considered the less disturbing than attaching it to their wrist perhaps). A 7-day sleep diary was recorded by the parents to note down sleep and nap times. Questionnaires also helped to find out about the sleeping arrangements, so whether the children were breastfeeding in the night, whether they had their own room, if they were put to sleep with formula, or co-sleeping with their parents.

What did they find?

Baby boys and girls had similar sleep. The more the children napped in the daytime, the less they slept at night. Interestingly though, the time the daytime nap ended didn’t impact on the total amount of night-time sleep. In fact the opposite happened, where the earlier the babies nap started the shorter night time sleep they had overall. When looking a little closer though, this may have been because those children who started their nap earlier, tended to nap for longer, which then would have reduced the amount of night-time sleep. They checked whether this was true by doing what is called a ‘mediation analysis’. This helps to see if the link between the time of napping and amount of night-time sleep had to do with the length of the nap, which it did.
They also ran a few other calculations on the data to check the likelihood of something happening, such as ‘Yes – the baby slept well’ Vs. ‘No – they didn’t’. When looking at a range of different things, such as sleeping arrangements, they found that only three things predicted a shorter amount of night-time sleep in toddlers on average, – these were:

• Longer naps during the day,
• Earlier nap times and
• Night-time breastfeeding.

In a nutshell:
1. It seemed to be the case that night-time breastfeeding interrupted the toddlers’ night-time sleep and reduced their amount of sleep overall. Unlike other research studies, co-sleeping arrangements did not seem to affect the amount of night-time sleep.
2. Longer daytime naps seem to make for a shorter amount of night-time sleep, which means that reducing the length of the daytime nap could actually improve children’s sleep.

We always need to consider these studies carefully though because there were a few problems, including:
• Sleep habits of parents weren’t considered, which are known to influence toddlers’ sleep habits.
• This study did not look into other possible causes, such as cultural and family differences, family income and parents’ educational background
• We can’t say that the longer the time toddlers nap during the day ‘causes’ them to have less sleep at night because this study only took all measurements at the same time, or a ‘snap-shot’ in time, when really you need to show daytime napping at one point in time leads to less sleep later on.


Title of lay summary Why won’t my toddler sleep? Audio lay Summary
Lay Summary Author(s)

Dr Anja Harrison

Vetting Professional Dr Anthony Harrison
Vetting Professional Affiliation(s) / participating organisation(s) 1
Science Area Subject
Key Search Words

Toddler sleep



Key Search Words for Expert Audience
Other relevant Collaborative Library lay summary links https://thecollaborativelibrary.com/busting-the-myth-of-the-28-day-menstrual-cycle-lay-summary/
What is the licence for your lay summary? Attribution-Non Commercial 4.0 International (CC BY-NC 4.0) (for all other options selected above)
If a pre-print or post-print, please provide a direct weblink or Digital Object Identifier(s) (DOI)):
Provide the full weblink DOI of the published scientific article: https://doi.org/10.1038/s41598-021-81970-6
Are there any other open-access data weblink(s) that might be helpful (e.g., for relevant data repositories see fairsharing.org):
Has this work been applied in ‘real-life’ settings (e.g., local service evaluation projects)? If so, add any relevant weblink(s) here:
Title of the original peer-reviewed published article: Daytime nap and nighttime breastfeeding are associated with toddlers’ nighttime sleep
Journal Name: Nature Scientific Reports
Year of publication: 2021

Machiko Nakagawa, Hidenobu Ohta, Rinshu Shimabukuro, Yoko Asaka, Takayo Nakazawa, Yoshihisa Oishi, Michio Hirata, Akiko Ando, Takashi Ikeda, Yuko Yoshimura, Yusuke Mitani, Yousuke Kaneshi, Keita Morioka, Rika Fukutomi, Kyoko Kobayashi, Miwa Ozawa, Masahiro Takeshima, Kazuo Mishima, Mitsuru Kikuchi, Kazutoshi Cho, Hitoshi Yoda & Isao Kusakawa

Contributors and funders:

no conflict of interest

Original Article language: English
Article Type: Cross-sectional Study / Prevalence study
What licence permission does the original e-print have? For more information on this please see our permissions video): Attribution 4.0 International (CC BY 4.0)

How did you find this lay summary?

Click on a star to rate it!

Average rating 5 / 5. Vote count: 2

No votes so far! Be the first to rate this post.

Related Articles


Is there something wrong here?

Only professional and non-professional contributors can request a review.

Request a review guide Report an issue

Fancy joining The Collaborative Library Working group?

We welcome people from diverse backgrounds.

No science background needed.

You have Successfully Subscribed!