Night-Shift Workers and Health
Shift work refers to a job schedule in which employees work hours other than the standard hours of 8 a.m. to 5 p.m. or a schedule other than the standard workweek – Monday through Friday in the USA.
Human beings are by nature a diurnal species with a natural tendency among adults to sleep at night and be most active during the day. Society is largely structured to facilitate such tendencies, with most social interactions, familial gatherings, and work hours during the daylight hours. However, there is often occasion to diverge from these norms especially for work purposes. Today’s society is driven by a 24 h mentality which demands that over 8.6 million people (in the USA) perform shift work (Kryger et al. 2005).
Circadian factors are a primary determinant of one’s ability to cope with shift work. Humans are biologically wired to sleep during the night and be most active during the day. Certain biological processes determine the body’s natural sleep–wake cycle, particularly the secretion of melatonin in response to the light–dark cycle. Such processes are not easily changed so as to shift the natural cycle. Some evidence indicates that sleep phase adjustment for a night worker, as measured by urine melatonin, can take as long as 5–6 days (90 min phase delay per day) before melatonin onset is readjusted to the new schedule.
In addition to endogenous determinants of the sleep cycle, there are other factors known as zeitgebers (time givers) that contribute to one’s perceived normal sleep–wake cycle. Such zeitgebers include social factors like meal times and social gatherings and natural factors like daylight and night. These timing cues help orient the body to a certain time schedule and to encourage humans to be active during the day. However, for a night-shift worker who must be awake during the night, these zeitgebers can work against an individual’s inclination to remain awake at night resulting in dysregulated immune, hormonal, and cardiovascular function, thereby contributing to poor health.
Domestic factors also play a big role in sleep and subsequent health of the shift worker. For the night worker, social, familial, and societal obligations often impinge on sleep time since they occur in opposition to the night worker’s schedule. Moreover, many shift workers have families and homes to care for that often require significant attention during daylight hours. Not only do these domestic factors inhibit a shift worker from obtaining adequate sleep during the day but they often impact the quality of the sleep he/she does get. Several consequences can arise from poor coping with a shift-work lifestyle, including a predisposition to depression and anxiety (Akerstedt 2003), as well as cardiometabolic stress and cognitive impairments (Kecklund and Axelsson 2016). Not surprisingly, shifting of one’s sleep to the daytime hours can have negative consequences (Akerstedt 2003). Not only is shift work (and daytime sleep) in contradiction to most of the biological system’s circadian rhythms, but it is a strong predictor in the development of chronic sleep disorders. For instance, shift workers have been found to have sleep maintenance insomnia as opposed to sleep onset insomnia, which results in a constant state of sleep deprivation. Surveys in Europe and in the USA have found that night workers get approximately 10 h less sleep per week than day workers. Akerstedt and colleagues found that there is a significant loss of Stage 2 and REM sleep among shift workers. Although a night worker’s sleep loss can be partially attenuated by sleeping longer on days off, they are unable to “repay the debt” and still experience chronic sleep deprivation and its consequences.
Health consequences of shift work include cardiovascular disease, diabetes, and obesity. There are also associations with stomach problems and ulcers, increased depression, and risk for injury or accidents. Many of these adverse outcomes stem from dysregulation of metabolic, digestive, and immune processes that maintain alignment with the circadian rhythm. While important and often necessary for many people to perform shift work, it is imperative to understand and appreciate the significant toll that shift work can have on health and social relationships (Akerstedt 1990).
References and Further Reading
- Kryger, M., Roth, T., & Derent, W. (2005). Principles and practice of sleep medicine. Philadelphia: Elsevier Saunders.Google Scholar