Association between night shift work and emotional cognition: a multicentre cross-sectional study

Background

Night shift work affects 15-20% of the European working population and disrupts circadian rhythms and cognitive functions. While cold cognition deficits are documented, evidence on emotional cognition (hot cognition) remains scarce, particularly regarding the role of shift intensity. This study aims to investigate the association between night shift work and hot cognitive functioning.

Methods

Cross-sectional study using data from the EPHOR-NIGHT multicentre cohort (Spain and Sweden). The analytical sample included 459 workers (225-day, 234-night) who completed the Dot Probe Task, measuring reaction time and attentional bias toward emotional stimuli. Multiple linear regression models were adjusted for age, sex, centre, education, smoking, chronotype and sleep quality. Shift intensity was examined as consecutive nights worked and number of nights per week.

Results

No overall associations were found between night shift work and reaction time or attentional bias. However, higher shift intensity showed a pattern of lower reaction times: workers with ≥3 consecutive nights (β = 20.7; 95%CI: -9.5; 50.3) and ≥4 nights/week (β = 23.4; 95%CI: -3.3; 50.1). A positive trend across increasing intensity levels was observed for both metrics of shift intensity (p-trend = 0.182 for consecutive nights and p-trend= 0.035 for nights per week) in fully adjusted models.

Conclusions

No clear association was observed between night shift work and hot cognition at average exposure levels. However, the observed pattern suggests that higher shift intensity may be associated with lower emotional processing speed which could have implications for decision-making and safety in shift work settings.

Key messages

• Night shift work may impair emotional processing speed, with implications for decisions-making and safety in healthcare and transport workers.

• Greater shift intensity shows a dose-response relationship with slower reaction times, suggesting emotional cognition thresholds ofte overlooked in standard night shift research.