Designing Light for Night Shift Workers: Application of Nonvisual Lighting Design Principles in an Industrial Production Line

Chronodisruption deteriorates the health and wellbeing of shift workers. Artificial light at night and the lack of light during the day are major contributors to chronodisruption and need to be optimized in shift work scenarios. Here, we present one solution for a lighting and automation system in an industrial production workplace. The setting is a rapidly rotating shift work environment with morning, evening, and night shifts. We describe a procedure to specify the new lighting through a software-agnostic nonvisual lighting simulation for artificial and daylighting scenarios. Through this process, a new luminaire is created, called Drosa, that allows for a large melanopic stimulus range between 412 and 73 lx melanopic equivalent daylight (D65) illuminance vertically at eye level, while maintaining a neutral white illuminance at task level between 1250 and 900 lx, respectively. This is possible through a combination of glare-free spotlights with adjustable areal wing lights. An individually programmed automation system controls the light dosage and timing during the day and night. The work is relevant for other shift work scenarios, where the presented example and the discussed rationale behind the automation might provide insights. The work is further relevant for other lighting scenarios beyond industrial shift work, as the nonvisual lighting simulation process can be adapted to any context.

Is shift-work associated with increased risk of rectal cancer? A meta-analysis.

e15600 Background: Globally, more than 1.8 million people were diagnosed of colorectal cancer (CRC) in 2018, with over 30% of CRC in the rectum. Shift-work, involving circadian disruption, sleep deprivation and lifestyle changes, was designated as a probable cause of cancer by The International Agency for Research on Cancer. Previous studies investigating the impact of permanent night-shift work and rotating shift-work on rectal cancer risk showed controversial results. Thus, this meta-analysis was conducted. Methods: A comprehensive literature search on PubMed was conducted to identify all relevant studies published prior to January 2021 according to the established inclusion criteria. The quality assessment was performed by the Newcastle-Ottawa Scale (NOS). The pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated to estimate the association between the shift-work and rectal cancer risk. Based on heterogeneity significance, random-effect or fixed-effect model was used. Subgroup analyses were conducted to explore the night-shift and rotating-shift, respectively. Sensitivity analysis and publication bias detection were performed, and trim and fill analysis was also conducted. All statistical analyses were performed using RevMan software (version 5.3; Cochrane library) and STATA 15.0 statistical software (Stata Corp., College Station, TX), and all P values were two-tailed, the test level was 0.05. Results: Thirty-seven articles were obtained from database searching. Three articles involving 1,063 rectal cancer cases were included. All studies were considered moderate to high quality. All included studies investigated on the association between shift-work and rectal cancer risk. A statistically significant association between shift-work and increased rectal cancer risk was found (OR 1.53, 95%CI: 1.31, 1.79, P< 0.00001, I 2 = 35%). In subgroup analyses, night-shift work was associated with a non-statistically significant increased risk of rectal cancer (OR 1.25, 95%CI: 0.47, 3.32, P = 0.66, I 2 = 93%). In contrast, Rotating-shift was associated with a statistically significant increased rectal cancer risk (OR 1.35, 95%CI: 1.10, 1.65, P = 0.004, I 2 = 6%). Sensitivity analysis confirmed the stability of the result. Funnel plot, Egger's test (t = 1.69, P = 0.341), and Begg's test (z = 1.04, P = 0.296) found no publication bias of analysis. Trim and fill analysis on fixed-effect model showed the pooled OR kept stable after adding two “missing” studies (OR 1.403, 95%CI: 1.224, 1.609, P <0.05). Conclusions: The current meta-analysis demonstrates that shift-work is associated with increased rectal cancer risk. However, no association between night-shift work and rectal cancer risk was found. In contrast, association between rotating-shift work and increased rectal cancer risk was found. More original studies on this topic are needed to further explore shift-work impacts on rectal cancer risk.

288 Chronotype-dependent impact of napping on sleep behavior in rotating shift workers

Introduction Rotating shift work is known to adversely impact sleep. Napping is one of the strategies that workers can use to mitigate the effect of shift work on their sleep. In this study, we investigated the effect of chronotype on napping behavior in police officers involved in rotating shift work. Methods Actigraphy-based sleep measures and chronotype information was available from 74 police officers (20 women and 54 men; age [mean ± SD]: 32 ± 5.4 years) that participated in a 35-day field study during which they worked morning, evening, and night shifts. A generalized linear mixed model was used to assess the effect of shift type, chronotype, and their interaction on the likelihood to take a nap, adjusted for relevant covariates. In addition, linear mixed models were used to determine the effect of shift type, chronotype, and their interaction on sleep duration with and without taking into account napping duration. Results The likelihood to take a nap was influenced by an interaction between shift type and chronotype (χ2(2) = 11.2, p = 0.004). Earlier chronotype was linked to a lower likelihood to take naps during days with morning shifts and a higher likelihood during days with night shifts. Napping modulated the effect of shift type and chronotype on daily sleep duration, most notably during night shifts: while chronotype was associated with the duration of the main sleep period during night shifts, with the main sleep period being 1.7 h [95% C.I.: 0.6 – 2.8] shorter in the earliest chronotypes compared to the latest chronotypes, this effect was attenuated and no longer significant when napping duration was taken into account (difference in total sleep duration in latest chronotypes vs earliest chronotypes during nights shifts: 0.9 [−0.1 to 1.9] h). Conclusion Napping attenuates the chronotype-dependent effect of atypical work schedules on sleep duration in this population of shift-working police officers. These findings highlight the need to take into account chronotype when assessing the effect of shift work on sleep behavior. Support (if any) The Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRRST) and Fonds de Recherche du Québec–Santé (FRQS).

The relationship between chronotype and sleep behavior during rotating shift work: a field study

Shift work, an essential part of our 24/7 society, inevitably leads to displacement of the habitual sleep period and thereby to misalignment of the internal circadian timing system with the rest–activity cycle and the environment. How interindividual differences in circadian organization affect sleep duration and timing during rotating shift work is not fully understood. The objective of this study was to assess the effect of chronotype, shift type, and their interaction on actigraphy-based sleep behavior in 74 police officers (20 women and 54 men; age [mean ± SD]: 32.1 ± 5.4 years) involved in rotating shift work throughout a 28- to 35-day work cycle consisting of morning, evening, and night shifts. Using linear mixed modeling, we found that chronotype was associated with sleep duration depending on the shift type: increasing morningness was correlated with longer sleep duration during series of consecutive morning shifts, while increasing eveningness was correlated with longer sleep duration during series of evening shifts. During series of night shifts, increasing eveningness was associated with a longer duration of the main sleep episode, but this relationship was attenuated and no longer significant when naps were taken into account due to increased napping in morning chronotypes during series of night shifts. Providing a detailed within-subject characterization of sleep behavior across a complete work cycle consisting of morning, evening, and night shifts, this study advances the understanding of the relationship between chronotype and sleep in rotating shift workers and supports the implementation of work schedules that take into account chronobiological principles.