Neurocognitive impairment in night and shift workers: a meta-analysis of observational studies

Shift work is an essential element of modern labour, ensuring ideal conditions of service for today's economy and society. Despite the beneficial properties, its impact on the neurobehavioural performance of exposed subjects remains controversial. This meta-analysis aimed to provide the first summarising effects regarding the association between shift work exposure and different cognitive functions.

A literature search was performed using the databases PubMed, PsyINFO, PsyARTICLES, MedLine, PsycNET and Scopus including eligible studies up to April 2021 that compared shift workers with non-shift workers regarding neurobehavioural performance tests. We carried out a random-effects model using Hedges' g as a meta-analytical effect size with a restricted likelihood estimator to summarise the mean differences between the exposure group and controls. Positive effect sizes indicate higher performance for non-shift workers. The heterogeneity of effect sizes was addressed by sensitivity analysis using funnel plots, Egger's tests, p-curve analysis, meta-regressions and subgroup analysis.

We included 18 studies resulting in a total sample of 18 802 participants and 37 effect sizes concerning six different neurobehavioural outcomes. Our results showed significantly worse performance in shift workers compared with non-shift workers in the following cognitive functions with g (95% CI): processing speed 0.16 (0.02 to 0.30), working memory 0.28 (0.51 to 0.50), psychomotor vigilance 0.21 (0.05 to 0.37), cognitive control 0.86 (0.45 to 1.27) and visual attention 0.19 (0.11 to 0.26).

We provide the first meta-analytical findings that associate shift work with decreased cognitive performance in processing speed, working memory, psychomotor vigilance, cognitive control and visual attention.