Industrialization has made it possible for people to work in shifts. Shift work involves a recurring nonstandard work schedule designed to meet a fixed daily work plan (Ledda et al., 2020). Approximately 20% of the working population currently works on shifts (Potter & Wood, 2020). Studies show that shift work causes premature biological aging due to various factors. Aging is a physiological process that progressively alters the biological structuring and functioning of the body. Ladde et al. underline the role of the Circadian Locomotor Output Cycles Kaput (CLOCK) gene in the body as the probable cause of biological aging (2020). Downregulation and disruption of the CLOCK gene have been linked to increased risks of various health conditions.
Shift work involves various physiological disruptions. The disruptions are due to the exposure of shift workers to irregular working periods including night shifts, weekend work, split shifts, on-call work, and extended duty periods (Costa, 2010). Some researchers argue that shift work accelerates biological aging due to the associated long-lasting health conditions and diseases.
Khan, Duan, and Hou (2018) highlight the role of shift work in breast cancer, colon cancer, and major depressive disorder among other disorders. Further, Ladde et al. propose that shift work has the potential to stimulate a series of alterations in DNA methylation, specific physiological organs, and epigenetic makeup which are linked to aging acceleration (2020). Some of the health risks associated with the night shift include cardiovascular diseases, high risk of human accidents, cancer, stroke, type-2 diabetes, neurodegenerative diseases, and disruptions of the biological rhythms and sleep (Potter & Wood, 2020; Carugno et al., 2021). All these potential health risks contribute to premature biological aging among workers in one way or another.
Disruption of sleep and circadian rhythms especially among those working on night shifts potentially influences the aging process. The correlation between night shift and circadian rhythm disruption is depicted by sleeplessness, reduced sleep time, and daytime weariness. Furthermore, studies indicate that shift work leads to sleep misalignment disturbing an individual’s cognitive functions (Ladde et al. 2020). These disruptions subsequently implicate human homeostasis and other biological processes which causes “shift-lag” syndrome (Costa, 2010). The syndrome is characterized by a lack of sleep, fatigue, irritability, and reduced mental nimbleness. If a person experiences the “shift-lag” syndrome for a prolonged period, their biological aging process accelerates.
The potential health issues linked to shift work include psychological and mental health problems. According to Costa (2010), common psychological and mental health problems among shift workers include irritability, uneasiness, and anxiety due to stressful working conditions.
Shift work and the accompanying irregular sleep patterns cause variation of the CLOCK gene. Circadian CLOCK is a gene sequence concerned with protecting the organization of many oscillators in the various organ systems in the body (Ladde et al. 2020). It is also responsible for the codification of CLOCK protein which regulates circadian processes. Besides, the CLOCK gene has a more extensive biological effect on cognition and temperament-related behaviors. According to Charrier et al. (2017), the variation of the CLOCK genes as a result of shift work especially night shifts has been linked to the increasing cases of psychiatric disorders such as “autism spectrum disorder, schizophrenia, anxiety disorders, major depressive disorder, bipolar disorder, and attention deficit hyperactivity disorder.” These physiological and pathological issues accelerate premature biological aging.
Gastrointestinal and metabolic disorders
Shift work interferes with the composition, timing, and frequency of meals. According to James et al., shift workers are forced to alter their mealtimes depending on their sleep-and-wake schedule. This interrupts the synchronization of leptin and ghrelin and misadjusts the subsequent biological systems correlated to food digestion and absorption (2017). The results are reduced leptin levels and dull after-meal suppression of ghrelin in the body. Reasons why most shift workers often complain about constipation, digestion snags, verbosity, pyrosis, gastric ulcers, and gut irritability (Costa, 2010).
Moreover, prolonged exposure to physiological maladaptation because of nutrition, meal timing, and metabolic disturbances, aspects widespread among shift workers, cause metabolic disorders. For instance, metabolic syndrome, type-2 diabetes, overweight, and obesity are more likely to manifest among shift workers compared to normal daytime workers. This is due to the reduced synchronization of mealtime and food digestion with the marginal liver and gut oscillators (James et al., 2017). Costa (2010) adds that these physiological conditions are characterized by increased cholesterol and decreased blood levels. While mediators such as nourishment, workout, and body mass are important, evidence shows that the overall connection between shift work and deprived metabolic health potentially contributes to premature biological aging.
Cancer and cardiovascular disorders are prevalent health risks associated with shift work. Ladde et al. categorizes shift work as carcinogenic to human beings and potentially causes cancers of the prostate, breast, and colon-rectal, and the growth of malignant tumors (2020). Additionally, shift working conditions pose a great risk for heart diseases such as hypertension (Costa, 2010).
Shift work triggers oxidative stress, a probable pathophysiological mechanism associated with age-related diseases and carcinogenesis. Oxidative stress causes damage to biomolecules such as nucleic acids, lipids, and proteins (Pavanello et al., 2019). The oxidative damage also involves the alteration of methylation patterns that erode telomere length and oxidize nucleic acids in the body. According to Pavanello et al, these oxidative processes cause impairment to cellular functions and are considered primary stamps of biological aging (2019). Most shift workers have enhanced inflammatory responses; this is not helped by work-related stimuli such as work stress. Chronic inflammation and physiological alterations accelerate the present high risk of age-related disorders and biological degeneration among shift workers.
Accidents and injuries
Another factor that promotes premature biological aging among shift workers is the increased cases of human errors, accidents, and injuries at work caused by lack of sleep, fatigue, and reduced attentiveness and caution levels (Costa, 2010). Other risky organizational factors such as heavy workloads, time pressure, and other unhealthy environmental conditions add to the injury risks. The health effects associated with work-related injuries and accidents cause a deterioration in the general well-being of shift workers impacting negatively on their biological aging.
Shift work is detrimental to the older population. According to Costa and Di Milia (2008), there is a noticeable sharp deterioration in several health aspects of shift workers aged 40 years and above. The deterioration can be linked to the fact that older shift workers have briefer and more troubled day sleeps between sequential night shifts than younger workers (Folkard, 2008). The high incidences of acute and chronic health issues among the older population working on shifts is a major factor associated with accelerated biological aging.
In conclusion, various studies have shown that shift work causes premature biological aging through the mediation of sleep cycle, metabolic, and physiologic disruptions. Shift work disrupts sleep and circadian rhythms, interferes with the composition, timing, and frequency of meals, and triggers oxidative stress. The associated common health risks include cardiovascular diseases, cancer, type-2 diabetes, psychiatric disorders, neurodegenerative diseases, gastrointestinal disorders, and accidents. These subsequently accelerate the biological aging process of an individual.