Shift schedules and circadian preferences: the association with sleep and mood

Front Public Health. 2024 Apr 29:12:1283543. doi: 10.3389/fpubh.2024.1283543. eCollection 2024.

Abstract

Object: We explored the circadian preferences of non-shift workers (non-SWs) and various types of shift workers (SWs), and the associations of these preferences with sleep and mood.

Methods: In total, 4,561 SWs (2,419 women and 2,142 men aged 37.00 ± 9.80 years) and 2,093 non-SWs (1,094 women and 999 men aged 37.80 ± 9.73 years) completed an online survey. Of all SWs, 2,415 (1,079 women and 1,336 men aged 37.77 ± 9.96 years) reported regularly rotating or fixed schedules ("regular SWs"), and 2,146 (1,340 women and 806 men aged 36.12 ± 9.64 years) had irregular schedules ("irregular SWs"). Of the regular SWs, 2,040 had regularly rotating schedules, 212 had fixed evening schedules, and 163 had fixed night schedules. All participants completed the Morningness-Eveningness Questionnaire (MEQ) exploring circadian preferences, the short form of the Center for Epidemiological Studies-Depression Scale (CES-D) evaluating depression, the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS).

Results: Compared to non-SWs, SWs had lower MEQ scores, i.e., more eveningness, after controlling for age, gender, income, occupation, and weekly work hours (F = 87.97, p < 0.001). Irregular SWs had lower MEQ scores than regular SWs (F = 50.89, p < 0.001). Among regular SWs, the MEQ scores of fixed evening and fixed night SWs were lower than those of regularly rotating SWs (F = 22.42, p < 0.001). An association between the MEQ and ESS scores was apparent in non-SWs (r = -0.85, p < 0.001) but not in SWs (r = 0.001, p = 0.92).

Conclusion: SWs exhibited more eveningness than non-SWs; eveningness was particularly prominent in SWs with irregular or fixed evening/night shifts. Eveningness was associated with sleepiness only in non-SWs, but not in SWs.

Keywords: circadian preference; depression; insomnia; shift work (MeSH); sleepiness.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Affect* / physiology
  • Circadian Rhythm* / physiology
  • Depression
  • Female
  • Humans
  • Male
  • Middle Aged
  • Shift Work Schedule / statistics & numerical data
  • Sleep* / physiology
  • Surveys and Questionnaires
  • Work Schedule Tolerance* / physiology
  • Work Schedule Tolerance* / psychology

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2022R1A2C2008417), the Bio & Medical Technology Development Program of the NRF funded by the Korean government (MSIT) (No. 2020M3E5D9080561), the Technology Innovation Infrastructure program through the Korea Institute for Advancement of Technology by the Ministry of Trade, Industry and Energy [No. P0014279], and the Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korean government (MSIT) (No. RS-2023-00221742).