Should Night Work Be ‘Managed’ or ‘Reduced’? – Setting the right direction for addressing night work (Jan. 2026)

Hye-Eun Lee, MD

Occupational and Environmental Medicine Specialist

Working Time Research Center

Korea Institute of Labor Safety and Health

2026

We have grown accustomed to a society where the lights never go out at night. There are essential public services like firefighting, policing, and hospitals, as well as continuous industrial processes like steel manufacturing and oil refining, that must operate around the clock. The problem lies in the fact that night work outside this ‘necessity’ has continued to expand. Nighttime has entered the work schedule to keep production facilities running longer, to meet deliveries faster, and to capture customers’ immediate consumption. In the 24/7 society symbolized by “open year-round” and “24-hour operation,” night work has become the norm, not the exception.

Recently, fixed night shifts have been expanding under the pretext of making night work “less painful.” Hospitals have increased number of permanent night shift nurses, citing the need to alleviate fatigue and turnover from rotating shifts. This practice of assigning fixed night staff has also emerged in other industrial settings. In the logistics industry, fixed night shifts are now considered more common than rotating shifts. However, this shift appears more aligned with labor management efficiency than with protecting workers’ health. Fixed night shifts are often utilized as a choice to simplify work schedules, reduce uncertainty in shift arrangements, and maintain stable daytime staffing. Regardless, since it involves working consistent hours, there is an expectation that it is better for health than rotating shifts where working hours constantly change. However, the assumption that ‘fixed’ means ‘adapted’ often proves to be false in reality. Fixed night shifts are less about adjusting the body to nighttime and more about locking both the body and society into a prolonged state of misalignment. There is a reason why workers say, “It feels like I am earning money by cutting years off my life.”

The steadfast rhythm of day and night. The body is hard to change, and society changes even less

The human body is built around biological rhythms. The rhythm of being awake during the day and sleeping at night is not merely a lifestyle habit, but a physiological order intertwined with hormone secretion, body temperature, metabolism, and immunity. It is easy to think that traveling far away will eventually allow the body to adjust to the time difference, but in work patterns that include night shifts, the statement “it is impossible to adapt” is repeatedly made. The same applies to fixed night work. Because the society surrounding the worker operates on a daytime clock, even if an individual completely flips their day and night, daily life pulls them back towards daytime.

Thus, the most immediate and directly apparent health issue in night work is sleep. Attempting to sleep in broad daylight is torture, and testimonies about the difficulty of getting sufficient sleep are common on the job. These include the feeling of lying down trying to force oneself back to sleep after waking, the claim of never having slept deeply, and the attempts to sleep more deeply by relying on alcohol. This is not a matter of individual constitution or weakness, but the violence of the conditions.

The argument that fixed night shifts may be preferable to rotating shifts rests on the premise that “once schedules are fixed, circadian rhythms will follow.” However, related studies reveal how fragile this premise is. A review study published in 2025 conducted a comprehensive assessment of existing evidence comparing fixed night shifts and rotating shifts to day workers, reporting a tendency for higher risks of cardiovascular and metabolic diseases in fixed night shift workers. Researchers attributed this finding to fixed night workers having greater exposure to night work than rotating shift workers. Conversely, cancer risk was relatively more pronounced in rotating shifts. Simply put, neither is a ‘safer alternative.’ They merely present different patterns of risk.

There is also more biological evidence. Melatonin, known as the ‘sleep hormone,’ is secreted more as it gets darker, inducing sleep, and is suppressed when it gets brighter. It is a key indicator that regulates the human biological clock, or the rhythm of night and day. A review study examining the adjustment of circadian rhythms in fixed night shift workers based on melatonin rhythms found that fewer than 3% of individuals showed complete adaptation to the reversed day-night schedule, and that even those showing some adjustment effects were limited.

The core finding of these studies is clear. While fixed night shifts may theoretically allow for “adaptation,” in reality, adaptation scarcely occurs. This is because fixed night shift workers also live within a society that operates on a day-night rhythm during their non-working hours. They must care for families and utilize daytime services like banks and hospitals. They struggle to sleep during the light-filled, noisy daytime, only to go back to work at night. Ultimately, fixed night shifts easily become a mechanism that perpetuates a chronic state of circadian misalignment over the long term.

Cardiovascular disease, mental health, accidents, and cancer

Sleep disorders are painful in themselves, yet they also serve as warning signs for subsequent problems.

Shift and night workers struggle to stay awake during work, making them prone to mistakes or accidents from nodding off. Night work also increases the risk of drowsy driving on the commute home, and studies report that risks can be even greater when workers force themselves to stay awake. A 2011 review study found that while individual studies varied, the risk of accidents increased by 30 to 100% during night shifts.

Mental health is no exception. Shift workers often struggle to maintain social relationships and experience weakened support networks. Consequently, studies consistently show an increased risk of mood disorders like depression and anxiety. There is also a reported tendency for this association to grow stronger with longer periods of shift work.

There is also the risk of cardiovascular and metabolic diseases. Night work can lead to persistent rhythm disruption, accumulated fatigue, difficulty of recovery, and challenges maintaining healthy habits like exercise and diet. While smoking cessation, moderate drinking, and exercise are often emphasized for preventing cerebrovascular disease, it is rarely acknowledged that these ‘individual lifestyle habits’ fundamentally depend on how time—a scarce resource—is allocated and controlled. Time is a factor that precedes personal willpower.

The health impacts of night work extend to increased cancer risk. In 2007, the International Agency for Research on Cancer (IARC) classified “shift work that disrupts circadian rhythms” as a probable human carcinogen (Group 2A). Initially, breast cancer drew attention, but subsequent reports also indicated risks for prostate cancer and colorectal cancer. The primary mechanism proposed for this carcinogenicity involves reduced antioxidant and anti-cancer effects due to suppressed melatonin secretion caused by light exposure during nighttime hours.

Night work is not a ‘work pattern’ but an ‘occupational hazard’

The most fundamental perspective of industrial safety and health is that once a risk factor is identified, it should be eliminated or structurally replaced. A prime example is the ban on asbestos use. In South Korea, asbestos was ultimately prohibited by law under a social consensus that its carcinogenicity and fatal health impacts were confirmed through extensive research, and that the risk could not be mitigated solely through personal protective measures or workplace-level management.

However, the reality is that the same logic does not apply to all hazards. Particularly for night work, societal responses remain confined to management and adaptation, justified by its perceived necessity. Society’s responsibility is obscured by the claim that workers “volunteered to work at night,” while high premiums merely mask the costs to health. Fixed night work hides its dangers more because the working times are the same every day. Considering that fixed night work disproportionately affects vulnerable workers, it is less a choice than a structural assignment.

Health management for night workers is not a technique to make them work nights “well.” It is about finding ways to eliminate night work altogether, restructuring working hours and staffing to reduce night shifts, minimizing unavoidable night work, and ensuring recovery. The response must go beyond health examinations and education; it must be designed to reduce night work. Society, not individual workers, should bear responsibility for unavoidable night shifts and ensure that they do not harm workers’ health. That is the starting point for managing the health impacts of night work.