Sleep symptoms are essential features of long-COVID – Comparing healthy controls with COVID-19 cases of different severity in the international COVID sleep study (ICOSS-II)

Ilona Merikanto, Yves Dauvilliers, Frances Chung, Yun Kwok Wing, Luigi de Gennaro, Brigitte Holzinger, Bjørn Bjorvatn, Charles M. Morin, Thomas Penzel, Christian Benedict, Adrijana Koscec Bjelajac, Ngan Yin Chan, Colin A. Espie, Harald Hrubos-Strøm, Yuichi Inoue, Maria Korman, Anne Marie Landtblom, Damien Léger, Kentaro Matsui, Sergio Mota-RolimMichael R. Nadorff, Giuseppe Plazzi, Catia Reis, Juliana Yordanova, Markku Partinen

Research output: Contribution to journalArticlepeer-review


Many people report suffering from post-acute sequelae of COVID-19 or “long-COVID”, but there are still open questions on what actually constitutes long-COVID and how prevalent it is. The current definition of post-acute sequelae of COVID-19 is based on voting using the Delphi-method by the WHO post-COVID-19 working group. It emphasizes long-lasting fatigue, shortness of breath and cognitive dysfunction as the core symptoms of post-acute sequelae of COVID-19. In this international survey study consisting of 13,628 subjects aged 18–99 years from 16 countries of Asia, Europe, North America and South America (May–Dec 2021), we show that post-acute sequelae of COVID-19 symptoms were more prevalent amongst the more severe COVID-19 cases, i.e. those requiring hospitalisation for COVID-19. We also found that long-lasting sleep symptoms are at the core of post-acute sequelae of COVID-19 and associate with the COVID-19 severity when COVID-19 cases are compared with COVID-negative cases. Specifically, fatigue (61.3%), insomnia symptoms (49.6%) and excessive daytime sleepiness (35.8%) were highly prevalent amongst respondents reporting long-lasting symptoms after hospitalisation for COVID-19. Understanding the importance of sleep-related symptoms in post-acute sequelae of COVID-19 has a clinical relevance when diagnosing and treating long-COVID.

Original languageEnglish
JournalJournal of Sleep Research
StateAccepted/In press - 2022
Externally publishedYes

Bibliographical note

Funding Information:
This study was funded by The Academy of Finland (project 322312, recipient Dr Merikanto), The Finnish Cultural Foundation (recipient Dr Merikanto), and the Signe and Ane Gyllenberg Foundation (recipients Prof. Partinen and Dr Merikanto). The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. There are no competing financial interests. Financial disclosure: none. Non‐financial disclosure: none.

Publisher Copyright:
© 2022 The Authors. Journal of Sleep Research published by John Wiley & Sons Ltd on behalf of European Sleep Research Society.


  • COVID-19
  • excessive daytime sleepiness
  • fatigue
  • insomnia
  • pandemic
  • post-acute sequelae of COVID-19

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Behavioral Neuroscience


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