Characterising studies to inform dietary recommendations for shift workers – a systematic review

This abstract was awarded the student prize for best oral presentation. Shift work is integral to the operational function of emergency service and first responder professions. However, it is associated with health consequences due to chronic disruptions in circadian rhythms, (1) sleep patterns (2) and less healthy diets. (3-4) Modifiable health behaviour interventions, such as improving diet quality, may be effective to prevent, mitigate or delay the onset of non-communicable diseases linked to shift work. (5) However, there is a lack of consensus on evidence-based guidelines. (3) This review aims to evaluate the evidence to support nutritional interventions in this population. A systematic review (PROSPERO CRD42023421400) was conducted to evaluate the literature that may inform dietary guidance for shift workers. Four databases were searched (Embase, Cochrane Library, Web of Science, PubMed). An additional three databases (Police MyAthens, ProQuest, Clinical Trials registries) were searched for relevant grey literature alongside a physical search at the National Police Library. Studies were screened by two researchers and included if of a randomised controlled trial (RCT), crossover-RCT, observational study design, conducted in free-living shiftwork populations or laboratory-controlled shiftwork setting. Papers were accepted where the intervention included a dietary component, and health-related outcomes were reported. Quality assessment was assessed using the Cochrane Risk of Bias Tools. Observational studies were evaluated using the Ottawa Scale. From the 6909 articles retrieved, 43 met the inclusion criteria. Most articles reported using a crossover design (49%), followed by observational studies (33%). Where specified, most studies involved free-living participants (67%) and were carried out with nursing and healthcare professionals (40%). Of included studies, 30% were conducted under simulated conditions. Only 9% of studies were conducted in first responder groups. Years in shift work were often not reported (40%) and, likely due to the prevalence of simulated protocols, a moderate number of studies involved participants with no shift work experience (28%). The quality assessment highlighted that 66% of the included papers were judged to be of concern (15%) or a high risk of bias (51%), signifying challenges to conducting research in shift working populations. The most frequently reported intervention components were Time-Restricted Eating (21%), macronutrient adjustments (21%), and food diaries (19%). The most frequently reported outcomes were cardiometabolic health (39.5%), cognitive performance (27.9%), and sleep quality (11.6%). Heterogeneity in interventions, outcome measures and reporting across studies made it difficult to synthesise findings to inform shift worker dietary guidelines. There was an under representation of studies conducted in first responder occupations and limited studies conducted in the UK. The high risk of bias re-iterates a requirement for more rigorous research to understand the complex relationship between shift work and first responders’ health. Addressing these limitations will help contextualise findings and inform development of evidence-based dietary strategies to mitigate the adverse health effects of shift work in this critical workforce.