Approximately 15 million Americans work on night shifts from time to time. This means that a considerable proportion of the adult population in America regularly interfere with their circadian rhythms while at work. Such workers may experience symptoms such as insomnia, fatigue, restlessness, depression, poor concentration, and disrupted metabolism among others. 
What is the Circadian Rhythm?
The Sleep Foundation defines circadian rhythm as “24-hour cycles that are part of the body’s internal clock, running in the background to carry out essential functions and processes.
The sleep-wake cycle is one of the circadian rhythms.
Naturally, our bodies are programmed to wind down to a slumber when darkness sets in and to arouse when the day breaks. This cycle is usually disrupted when one is working a night shift and this may result in a sleep disorder if the disruption persists for a prolonged duration. [1, 2] Regardless of how much one sleeps during the day, they may still feel fatigued and restless when they wake up because their body is not in sync with the circadian rhythm. In other words, circadian misalignment cannot be restored by daytime sleeping. 
In the regular sleep wake cycle, individuals are awake when there is daylight and drift to sleep as darkness sets in. The biological clock is programmed to be in sync with the regular sleep-wake/ light-dark cycle. Light during the day fuels alertness and increased concentration while the reverse happens during the night when the body naturally shuts down.  When working night shifts, the body is forced to go against the circadian drive for alertness and wakefulness. This means that it takes more effort to be awake during the night shift and to fall asleep during the daytime. This can easily decimate to a state of total chaos when the body is unable to cope with the increased pressure to perform against the grain. .
What Happens When One’s Circadian Rhythm is Disrupted
Circadian misalignment occurs when the circadian rhythm (biological clock) is not in sync with sleep/ wake cycle.
Fatigue, low moods, decreased cognitive abilities, and impaired metabolism are symptoms that may present. Work performance is usually affected adversely and this may be associated with an increased risk for workplace accidents.
Prolonged shift work causes circadian misalignment which not only affects regular sleep patterns but it also determines people’s ability to exercise, eat, socialize, and even have sex. When these factors compound the result may be chronic health outcomes such as metabolic and gastrointestinal disorders. Cancer, heart complications and mental disorders are also likely complications.
Work shifts need to be planned in light of the underlying adverse effects that may occur when the circadian and homeostatic processes that regulate sleep are interfered with. This may not necessarily mean completely doing away with such shifts but instead giving maximum support to employees as they adjust to and from on a regular basis.
1- James, S. M., Honn, K. A., Gaddameedhi, S., & Van Dongen, H. (2017). Shift Work: Disrupted Circadian Rhythms and Sleep-Implications for Health and Well-Being. Current sleep medicine reports, 3(2), 104–112.
2- Akerstedt T. (2003). Shift work and disturbed sleep/wakefulness. Occupational medicine (Oxford, England), 53(2), 89–94.
3- Van Dongen, H. P., & Dinges, D. F. (2005). Sleep, circadian rhythms, and psychomotor vigilance. Clinics in sports medicine, 24(2), 237–viii.
4- Dijk, D. J., & Czeisler, C. A. (1994). Paradoxical timing of the circadian rhythm of sleep propensity serves to consolidate sleep and wakefulness in humans. Neuroscience letters, 166(1), 63–68.