The Secret of the Night Shift

    The circadian rhythm is commonly known as the body’s internal clock that runs in 24-hour cycles. This cycle is modulated by internal biological processes, behavioral activities, and environmental factors (Fishbein et al., 2021). Circadian disruption is the disturbance of this internal clock and has been correlated to numerous health disorders (Fishbein et al., 2021). In the US alone, 16% of nondaytime employees, 70% of indoor employees, 99% of the population affected by light pollution, and adults above 65 are at risk for circadian disruption (Fishbein et al., 2021). Therefore, circadian disruption poses a growing concern for the world. Fishbein, Knutson, and Zee emphasize circadian disruption's many psychological and physiological impacts. Pavanello et al. further this discussion by looking at the effects of night shift work on the health of 150 hospital workers. 

    Pavanello et al. used the work ability index (WAI) to determine how the employees perceived their abilities to handle the demands of their jobs and their coping ability with that work. Therefore, individuals with a high WAI perceive themselves to have higher work ability. The study found that the people with upper levels of work ability were young and healthy. These individuals were also more likely to do demanding tasks and work more night shifts (Pavanello et al., 2019). By analyzing urine samples and telomere length, the study found that the upper levels of workability correlated to higher oxidative damage and shorter telomere length (Pavanello et al., 2019). Oxidative damage is an important factor to consider because it has been correlated with many of the disorders that Fishbein, Knutson, and Zee emphasize to be caused by circadian disruption (Fishbein et al., 2021). Disorders associated with circadian disruption include neurodevelopmental, neurodegenerative, mood, metabolic (diabetes), and cardiovascular disorders (Fishbein et al., 2021). It has been hypothesized that the cause of this high oxidative damage is a reduction in antioxidative enzymes. Melatonin helps induce the production of these enzymes; however, when circadian rhythms are disrupted, melatonin production is also disrupted (Pavanello et al., 2019). Telomeres are repeated DNA sequences at the end of chromosomes that protect genes at the ends of chromosomes from being left unreplicated due to a limitation in the DNA polymerase enzyme (Pavanello et al., 2019). This region of the chromosome is susceptible to oxidative damage and can explain the shorter telomeric regions found in workers with high scores on the WAI. 

    The importance of the Pavanello et al. study is that it shows a clear correlation between night shift work and the damage it causes to the employee’s body. A more concerning discovery of the study is that it predicts future illnesses in healthy younger working employees. Healthier employees show a higher risk of future diseases due to oxidative damage and telomere shortening (Pavanello et al., 2019). In their review paper, Fishbein, Knutson, and Zee discussed methods to treat circadian disruption. One strategy is to use melatonin supplementation a few hours before bedtime, and a study has shown an improvement in sleep quality in children with autism (Fishbein et al., 2021). Light therapy has also increased sleep quality, reduced neuroinflammation, and reduced oxidative stress (Fishbein et al., 2021). Future therapies must test these therapies in night shift employees and help them engage in preventative measures for future illness. 

Citations: 

Fishbein, A. B., Knutson, K. L., & Zee, P. C. (2021). Circadian disruption and human health. Journal of Clinical Investigation, 131(19). https://doi.org/10.1172/jci148286 

Pavanello, S., Stendardo, M., Mastrangelo, G., Casillo, V., Nardini, M., Mutti, A., Campisi, M., Andreoli, R., & Boschetto, P. (2019). Higher number of night shifts associates with good perception of work capacity and optimal lung function but correlates with increased oxidative damage and telomere attrition. BioMed Research International, 2019, 1–10. https://doi.org/10.1155/2019/8327629