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Association between matched chronotype and poor mental health among shift workers: a systematic review and meta‐analysis
  1. Beixi Li1,
  2. Gengze Liao1,
  3. Priscilla Ming Yi Lee1,2,
  4. Anke Huss3,
  5. Yuen Ting Julie Ma1,
  6. Joey Wing-Yan Chan4,
  7. Yun Kwok Wing4,
  8. Lap Ah Tse1,5
  1. 1 JC School of Public Health and Primary Care, The Chinese University, Hong Kong SAR, People's Republic of China
  2. 2 Department of Clinical Medicine-Department of Clinical Epidemiology, Aarhus Universitet, Aarhus, Denmark
  3. 3 Department of Population Health Sciences, Utrecht University, Utrecht, Netherlands
  4. 4 Department of Psychiatry, The Chinese University, Hong Kong SAR, People's Republic of China
  5. 5 Shenzhen Municipal Key Laboratory for Health Risk Analysis, Shenzhen Research Institute of the Chinese University of Hong Kong, Shenzhen, People's Republic of China
  1. Correspondence to Professor Lap Ah Tse, JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China; shelly{at}


Background Nearly 0.7 billion workers are involved in the shift work system, leading to concerns about its potential impacts on the large-scale population mental health. This study aimed to synthesise evidence of the associations between matched chronotype and the risk of poor mental health among shift workers.

Methods Six computerised databases were searched from inception to September 2022. Observational studies were selected if they reported any association between common mental health parameters and chronotype scores/types of shift workers. The Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist was followed. We extracted adjusted risk estimates to calculate pooled effect sizes and explore sources of heterogeneity. The study was registered in PROSPERO: CRD42022357437.

Results Fourteen studies including 49 909 workers were identified. Ever shift workers had a higher risk of poor mental health than the day workers (pooled OR 1.15, 95% CI 1.03 to 1.28; I2=14%, p=0.29), with the evening chronotype ever shift workers having a 1.47 times higher risk than those who worked during the day (pooled OR 1.47, 95% CI 1.13 to 1.91; I2=42%, p=0.16). Sensitivity analysis excluding studies with the highest risk of bias of each group demonstrated consistent findings.

Conclusions Evening chronotype ever shift workers have poorer mental health than shift workers with other chronotypes. Chronotype remains unrecognised in the contemporary rostering system, making it a hidden contributor to occupational mental health. Work-related physical and mental stresses may be prevented/mitigated with further investigation on optimising shift work schedule combined with individual chronotype preference.

  • mental health
  • meta-analysis
  • occupational health

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Data availability statement

Data are available on reasonable request.

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  • BL and GL contributed equally.

  • Contributors LAT is the guarantor of the manuscript and is the principal investigator of the project, designed and supervised the entire study. BL designed the study, reviewed the literature, extracted and analysed the data, and drafted the manuscript. GL reviewed the literature, extracted the data, and reviewed the manuscript. YKW, JWYC and AH critically reviewed and revised the manuscript. PMYL and JYTM gave comments and reviewed the manuscript.

  • Funding The Health and Medical Research Fund (Ref. No. 18190471), the Research Grants Council-General Research Fund (RGC Ref. No. 14604020) of the Hong Kong Special Administrative Region, and lnt'l TripartiteCollaboration to Advance Exposome Research-lnnovative Public Health Exposome Global Projects and BioData Approach of the Chinese University of Hong Kong (Ref. No. EC/2017/006), Hong Kong Special Administrative Region, China.

  • 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.