Heidi M. Lammers-Van der Holst

This qualitative descriptive study aimed to explore dietary habits among healthcare workers during night shifts and to identify individual and environmental factors that influence their dietary behaviour during night shifts. Individual semi-structured interviews were conducted with twenty-five healthcare night female workers, which were recruited via email invitations from managers and posters placed in central workplaces at a university medical centre in the Netherlands. The interview protocol was developed following an integrated behaviour change model focusing on individual (I-Change model, i.e., awareness, motivation, intention, and ability) and environmental (Environmental Research framework for weight Gain prevention at environmental level (EnRG), i.e., physical, policy-related, economic, and sociocultural) factors. Inductive analyses were conducted to explore dietary habits, while deductive thematic analysis was applied to identify potential factors influencing dietary behaviour. Female healthcare workers in night shifts generally made poorer dietary choices during night shifts than during other shifts. Seven key themes were coded for dietary behaviour. Based on the domains of the integrated behaviour change model, four individual and five environmental key themes were established, within which 41 sub-themes were coded. Key individual factors included awareness (i.e., lack of knowledge about timing and type of consumption) and motivation (i.e., attitude and efficacy to eat healthy). Critical environmental factors included physical and sociocultural work environment, organisation of work, and lack of organisational policies. To conclude, future dietary interventions for healthcare night workers should target both individual behaviours and the workplace environment, with an emphasis on raising awareness and enhancing organisational policies to promote healthy dietary habits.

Summary: Shift work can cause circadian misalignment, which often results in sleeping problems and has been associated with immune dysfunction. To better understand the impact of shift work on a primary immune response to vaccination, we compared severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2)‐specific humoral and cellular immune responses after one injection of the messenger RNA (mRNA)‐1273 vaccine between day workers ( n = 24) and night shift workers ( n = 21). In addition, duration and quality of sleep were assessed for a period of 7 days around the time of vaccination using actigraphy and daily sleep diaries, and their relationship with immunogenicity of mRNA‐1273 vaccination was studied. We found that median total sleep time on the 2 days immediately after vaccination, which coincided with the days that night shift workers worked night shifts, was significantly lower in night shift workers (342 and 318 min) than day workers (431 and 415 min) (both p < 0.001). There was no difference in sleep quality between day workers and night shift workers. Furthermore, no difference in the antibody response between the two groups was observed, yet night shift workers had a significantly higher virus‐specific T‐cell response than day workers 28 days after immunisation ( p = 0.013). Multivariate regression analysis showed no association between sleep duration, sleep quality and SARS‐CoV‐2‐specific humoral or cellular immune responses. Collectively, these findings indicate that shift work‐induced sleep loss and night shift work have little to no effect on the primary immune response to mRNA‐based COVID‐19 vaccination.

Nurses are at a high risk for short sleep duration and poor sleep quality due to irregular work schedules and high occupational stress. Considering the effect of nurses' sleep on the safety and health of themselves and their patients, it is important to promote healthy sleep for nurses. We sought to synthesize the published experimental and quasi‐experimental studies that address interventions to improve sleep in nurses. A systematic search was conducted for studies published in English up until May 15, 2023, using the databases PubMed, CINAHL, Academic Search Ultimate, and PsycINFO. In total, 38 articles were included, covering 22 experimental and 16 quasi‐experimental studies with sample sizes ranging from 9 to 207. Studies were assessed using the Cochrane Risk of Bias tool and considered as low to medium quality. Thirty‐six of the 38 studies reported positive findings for at least one sleep outcome. Intervention types included aroma therapy, dietary supplements, cognitive behavioral therapy, light therapy, mind‐body therapy, sleep education, exercise, napping, shift schedule modification, and multicomponent intervention, all of which showed moderate effectiveness in promoting sleep outcomes of nurses. Comparing and contrasting studies on specific interventions for improving sleep in nurses is sparse and often equivocal. With the variations of research methodology and outcome measures, it is difficult to make a conclusion about each intervention's effectiveness on specific sleep outcomes. Additional high‐quality research, including randomized controlled trials, is needed to evaluate strategies for improving sleep in this unique, safety‐sensitive occupational group.

Sleep and circadian rhythms are closely involved in the immune system and its regulation. Here, we describe this relationship and provide recommendations regarding the influence of sleep and circadian rhythms on vaccination success. We review studies investigating how viral susceptibility is influenced by changes in immunological parameters as a consequence of sleep deprivation. Short sleep duration and poor sleep efficiency both appear to be strong factors leading to greater vulnerability. In addition, both sleep duration and the time of day of the vaccination seem to be associated with the magnitude of the antibody response after vaccination. Based on these findings, a recommendation would consist of a sleep duration of 7 h or more every night to both reduce the risk of infection and to optimize the efficacy of vaccination with respect to circadian timing. Improving sleep quality and its circadian timing can potentially play a role in preventing infection and in vaccination benefits. In conclusion, sufficient (or longer) sleep duration is important in both reducing susceptibility to infection and increasing antibody response after vaccination.

Summary: This protocol describes an innovative study to investigate the relationship between sleep, shift work and the immune response to severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2; coronavirus disease 2019 [COVID‐19]) vaccination. As the COVID‐19 pandemic is a global crisis with devastating health, social and economic impacts, there is a pressing need for effective vaccination programmes. Previous influenza and hepatitis vaccination studies suggest that lack of sleep can negatively alter immune responsiveness, while circadian misalignment most likely may also play an important role in the immune response to vaccination. Our present study will be the first to address this question in actual shift workers and in relation to COVID‐19 vaccination. We hypothesise that the occurrence of recent night shifts and diminished sleep will negatively alter the immune response to vaccination in shift workers compared to dayworkers. We aim to recruit 50 shift workers and 50 dayworkers. Participants will receive an mRNA‐based vaccination, through the Dutch vaccination programme. To assess immune responsiveness, blood will be drawn at baseline (before first vaccination), 10 days after first vaccination, the day prior to the second vaccination; and 28 days, 6 and 12 months after the second vaccination. Actigraphy and daily sleep e‐diaries will be implemented for 7 days around each vaccination to assess sleep. The Pittsburgh Sleep Quality Index will be used to monitor sleep in the long term. Optimising the efficacy of the COVID‐19 vaccines is of outmost importance and results of this study could provide insights to develop sleep and circadian‐based interventions to enhance vaccination immunity, and thereby improve global health.

Circadian misalignment remains a distinct challenge for night shift workers. Variability in individual sleep-wake/light-dark patterns might contribute to individual differences in circadian alignment in night shift workers. In this simulation study, we compared the predicted phase shift from a mathematical model of the effect of light on the human circadian pacemaker to the observed melatonin phase shift among individuals who completed one of four interventions during simulated night shift work. Two inputs to the model were used to simulate circadian phase: sleep-wake/light-dark patterns measured from a wrist monitor (Simulation 1) and sleep-wake/light-dark patterns measured from a wrist monitor enhanced by known light levels measured at the level of the eye during simulated night shifts (Simulation 2). The estimated phase shift from the model was within 2 hours of the observed phase shift in ~80% of night shift workers for both simulations; none of the model-predicted phase shifts was more than ~3 hours from the observed phase shift. Overall, the root-mean-square error between observed and predicted phase shifts was better for Simulation 1. The light input from the wrist monitor informed by actual light level measured at the eye performed better in the sub-group exposed to bright light during their night shifts. The findings from this simulation study suggest that using a mathematical model combined with sleep-wake and light exposure data from a wrist monitor can facilitate the design of shift work schedules to enhance circadian alignment, which is expected to improve sleep, alertness, and performance.

This study aimed to examine prospectively whether individual nighttime sleep characteristics at baseline (prior to shift‐work exposure) are related to parameters of daytime sleep after commencing shift work. A longitudinal field study was carried out with novice police officers of the Dutch Police Force. A total of 26 subjects were examined at baseline before they entered shift work and re‐examined during follow‐up sessions after four and twelve months of shift‐work exposure. Wrist actigraphy and sleep diaries were used to study nocturnal sleep at baseline and daytime sleep after night shifts during follow‐up sessions. As outcome variables, estimated total sleep time, sleep efficiency, and subjective sleep quality were analyzed. Daytime total sleep time showed a 66 min decline during the first year of shift‐work exposure. Systematic inter‐individual differences were observed for daytime total sleep time and subjective sleep quality (explaining 53% and 38% of the variance, respectively), suggesting potential predictability of these sleep parameters. Although no predictors were found for daytime total sleep time, the subjective quality of nighttime sleep before the onset of shift work predicted 40% of the variance in the subjective quality of daytime sleep after commencing shift work. Follow‐up studies may reveal whether the subjective quality of baseline nighttime sleep also predicts long‐term overall tolerance for shift work.