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COVID-19 pandemic and language development in children at 18 months: a repeated cross-sectional study over a 6-year period in Japan
  1. Rumi Matsuo1,
  2. Naomi Matsumoto2,
  3. Toshiharu Mitsuhashi3,
  4. Takashi Yorifuji2
  1. 1Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
  2. 2Department of Epidemiology, Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
  3. 3Center for Innovative Clinical Medicine, Okayama University Hospital, Okayama, Japan
  1. Correspondence to Dr Rumi Matsuo, Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan; pkjg52ww{at}


Objective To evaluate the impact of the COVID-19 pandemic experience on language development among children, we compared language development at 18 months of age, before and during the pandemic in Japan, where strict control measures continued over a long period.

Methods This was a repeated cross-sectional study and we included children who attended the 18-month health check-up provided by the Okayama City Public Health Center between January 2017 and December 2022 (n=33 484). We compared indicators of language development before (from January 2017 to February 2020) and during (from March 2020 to December 2022) the pandemic. Our primary outcome was the proportion of children who required follow-up for language development by the Public Health Center. The secondary outcome was the proportion of children who could not say three or more meaningful words. We estimated risk ratios (RRs) and their 95% CIs, adjusted for potential confounders.

Results The prevalence of the primary outcome was 33.5% before the pandemic and 36% during the pandemic. Compared with before the pandemic, increased RRs for the primary and secondary outcomes were observed during the pandemic, with RRs (95% CIs) of 1.09 (1.06–1.13) for the primary outcome and 1.11 (1.05–1.17) for the secondary outcome. Although the statistical interactions were not significant, the RRs were higher for children cared for at home than those in nursery schools and with ≤3 family members than those with ≥4 family members.

Conclusions The COVID-19 pandemic was associated with an increased risk of impaired language development in children at 18 months. More extensive support is needed for higher risk families, as well as follow-up of long-term language development in children affected by the COVID-19 pandemic.

  • Child Development
  • Child Health
  • Covid-19
  • Paediatrics

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  • Contributors RM analysed the data and wrote the first draft. NM, TM and TY contributed to the interpretation of the data and revised the manuscript. TY is the guarantor of the article.

  • Funding This work was supported by a grant from Okayama Prefecture for investigating the COVID-19 outbreak (Grant No 7402300018).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.