Why circadian rhythmicity matters: Associations between sleep irregularity and mental health conditions during the Covid-19 health crisis

Abstract

Objective

To assess the association between sleep irregularity, anxiety, and depression while controlling for other sleep dimensions and using a longitudinal design.

Methods

Longitudinal cohort study which started in April 2020 during the first French lockdown in the general population. Follow-up questionnaires were completed in June 2020, a period without lockdown measures. Participants were asked about their sleep (regularity, duration, timing, complaints) and their anxiety (General Anxiety Disorder-7) and depressive (Patient Health Questionnaire-9) symptoms.

Results

A total of 3745 participants were included (mean age: 28.9 years) with 2945 women (78.6%). At baseline, 38.1% (1428) of participants reported irregular sleep timing, 23.8% (891) anxiety and 28.9% (1081) depressive symptoms. In cross-sectional analyses, irregular sleep timing was associated with a 2.5-fold higher likelihood of anxiety and a 4-fold higher likelihood of depressive symptoms compared to regular sleepers. Associations were not explained by the other sleep dimensions and persisted in a longitudinal analysis, with irregular sleep timing at baseline being associated with anxiety (OR = 3.27[1.58–6.76]) and depressive symptoms (OR = 3.45[1.66–7.19]) during follow-up.

Conclusion

The results show a strong association between sleep irregularity and mental health. Furthers studies are needed to explore how sleep regularity could promote good mental health in non-clinical populations.

Keywords:

• Sleep regularity
• sleep health
• mental health
• Covid-19 health crisis

Acknowledgments

We wish to thank all members of the CONFINS group including the i-Share, Kappa Santé and Kap Code team members: Christophe Tzourio, Stéphane Schück, and Nathalie Texier conceived and designed the study cohort; Edwige Pereira, Garance Perret, Aude Pouymayou and Mathilde Pouriel managed the database; Julie Arsandaux, Shérazade Kinouani, Mélissa Macalli and Ilaria Montagni wrote and revised survey tools and manuscripts; Raphaël Germain and Clothilde Pollet were in charge of the regulatory aspects; Vanessa Marie-Joseph, Adel Mebarki, Elena Milesi and Marie Mougin were in charge of study communication and dissemination. The authors are also grateful to all the participants who volunteered to take part in the study.

Author contributors

All authors have seen and approved the manuscript. Concept and design: Christophe Tzourio. Acquisition: Christophe Tzourio. Statistical analysis: Julien Coelho. Interpretation of data: Julien Coelho, Ilaria Montagni, Christophe Tzourio, Sabine Plancoulaine. Drafting of the manuscript: Julien Coelho, Ilaria Montagni. Critical revision of the manuscript for important intellectual content: Ilaria Montagni, Christophe Tzourio, Jean-Arthur Micoulaud-Franchi, Pierre Philip, Jacques Taillard, Sabine Plancoulaine. Supervision: Christophe Tzourio.

Data deposition

The data underlying this article cannot be shared publicly for the privacy of individuals that participated in the study. The data will be shared on reasonable request to the corresponding author.

Ethical standards

The cohort was approved by the French Committee for the Protection of Individuals (Comité de Protection des Personnes—CPP, nr. 46-2020) and the French National Agency for Data Protection (Commission Nationale Informatique et Libertés—CNIL, nr. MLD/MFI/AR205600), and the data are stored and analysed according to the General Data Protection Regulation (EU GDPR). The study was conducted in accordance with the Declaration of Helsinki.

Statement of interest

None to declare.

Additional information

Funding

The i-Share team is currently supported by an unrestricted grant of the Nouvelle-Aquitaine Regional Council (Conseil Régional Nouvelle-Aquitaine, Grant No. 4370420). It has also received grants from the Nouvelle-Aquitaine Regional Health Agency (Agence Régionale de Santé Nouvelle-Aquitaine, Grant No. 6066 R-8), Public Health France (Santé Publique France, Grant No. 19DPPP023-0), and The National Institute against cancer INCa (Grant No. INCa_11502). The funding bodies were not involved in the study design or in the collection, analysis, or interpretation of the data.