Introduction: Approximately 20–25% of the global population is engaged in shift work. Shift work
has no consensus definition but can be conceptualised as any work schedule that involves
work outside traditional daytime hours (i.e., ~8 am to ~6 pm). Therefore, shift work encompasses morning, evening and night work, as well as rotating,
permanent and irregular schedules. It is well established that the sleep loss and
circadian disruption associated with shift work results in adverse health, psychosocial
wellbeing and safety outcomes. As humans are day active, night work poses the greatest
challenge to the circadian system. As such, many health and safety regulators and
labor organisations worldwide encourage special provisions for health assessments
for night workers, and some provide guidance to avoid permanent night work. We conducted
a systematic review to evaluate the differential effects of permanent night work (PNW)
and rotating shift work that includes night shifts (RWN) on health, safety and performance.
Methods: PubMed, CINAHL, PsycINFO, Medline and Scopus databases were searched for peer-reviewed
scientific studies published between 1990 and 2024 that evaluated health, wellbeing,
safety or performance outcomes in both PNW and RWN. Study quality was appraised using
JBI critical appraisal checklists. Thirty-eight studies were included in the overall
review, and three examined mental health outcomes.
Results: The design and quality of the reviewed studies that examined mental health varied
considerably. The reporting of shift work schedules was poor in all studies, and details
regarding exposure to night work were excluded, making evaluation difficult. While
the sample size in two studies was sufficient to evaluate associations, one study
had a very small sample size (n = 136). The sample of night workers in each study was comparatively small (2.3–7.4%
of the overall sample). The studies suggest that compared with day work, PNW is associated
with greater odds of having a mood disorder or reporting suicidal ideation, whereas
RWN showed no association.
Conclusion: Few studies have examined the differential effects of PNW and RWN on mental health,
and assessment of study quality suggests the findings should be interpreted with caution.
Future studies must capture and adjust for night work exposure to determine differential
effects. Support: The study was funded by the Civil Aviation Authority of New Zealand.
