Working long hours at night doubles health risks: study

Workers at a local farm are seen in this photo taken on July 16 in Gangneung, Gangwon Province. (Yonhap)

Shift work, nighttime work, and longer working hours could be more than twice as harmful on one's physical and mental health compared to those with regular working conditions, a study by a government-affiliated think-tank showed Thursday.

The recent report by the Occupational Safety and Health Research Institute researched the detrimental effects of what it called "irregular labor conditions," and found that those working in shifts, long hours and at night are 129 percent more likely to develop problems with their physical health than those working standard hours.

A combination of shift work and nighttime work raised the health risk by 53.1 percent, while shift work and long hours raised it by 128 percent.

Researchers used the data from a 2023 survey on 38,599 employees across the country. A total of 6,102 workers (15.8 percent) worked under irregular conditions.

The study defined long hours as working for more than 48 hours a week — referring to the regular 40-hour week plus an eight-hour extension. Nighttime hours meant full-time hours that included the period between midnight and 5 a.m. at least four times a week.

The subjects with irregular working conditions consistently had higher health risks compared to those with regular working conditions. While long hours was biggest risk factor of the three the researchers highlighted, even those who just worked irregular shifts were 23.7 percent more likely to have problems with their physical health than the control group.

Mental health, on the other hand, did not rise significantly among groups that worked irregular shifts, even if these included nighttime shifts.

But it could exacerbate the effects on those working long, nighttime hours, who saw the risks to their mental health shoot up.

Those working long hours and at night had a 86.1 percent higher risk of developing mental health issues, rising to 90.4 percent if they also worked irregular shifts.

The group that just worked night shift was 22.6 percent more likely to have mental health issues.

"Unlike for physical health, groups working night shift were at more risk," the researchers noted.

Sufficient rest, intensity of labor are important factors

The study also looked at other factors, including the characteristics of the worker like gender and age, mistreatment such as violence and discrimination, and the nature of the work itself. It found that the intensity of labor was an important factor for both physical and mental health, and that flexible work hours for the laborers to acquire sufficient rest was important to address the health issues.

As such, the researchers called for clear legal clauses to guarantee those that work late, for long hours, and in irregular shifts enough time to recover physically and mentally. The study suggested that there needs to flexibility in the workplace to allow workers to rest when they need it, citing other countries that make greater effores to enssure workers get enough rest after nighttime work.

Other factors included fair compensation for the work and support of their colleagues and superiors.

"Through other researchers and the results of this study, we have made suggestions such as restricting overtime work exceeding eight hours, at least 11 hours of rest in such cases for physical and mental recovery, along with broadened criteria on which laborers are subject to special health inspections (to include those on irregular hours)," the study said.