Study details

For the study, researchers at South Korea's Chung-Ang University and Yonsei University followed 110 healthcare workers and split them into "overworked" and "non-overworked" groups.

In South Korea, 52 hours is the legal upper limit of work per week, so researchers considered those who worked at least 52 hours a week as "overworked." The overworked group consisted of 32 people who were on average younger, employed for less time, and more highly educated compared to those working standard hours.

The researchers then compared data from a different study alongside MRI scans, allowing them to use a neuroimaging technique to analyze each worker's brain volume.

This helped the researchers identify and compare differences in levels of gray matter in various regions of the brain. The researchers also applied atlas-based analysis to allow them to identify and label structures in brain scans.

"The increased brain volumes observed in overworked individuals may reflect neuroadaptive responses to chronic occupational stress, although the exact mechanisms remain speculative," the researchers said.

Discussion

The researchers said they believe their findings suggest a "potential relationship" between an increased workload and changing different parts of the brain, which provides a biological basis for the cognitive and emotional challenges often reported by overworked people.

Joon Yul Choi, an assistant professor at Yonsei University's Department of Biomedical Engineering and co-author of the study, said that these changes could be "at least in part, reversible" if environmental stressors are reversed. However, returning to your brain's baseline state could take much longer.

Frank Pega, a technical office at the World Health Organization who led a study in 2021 on the health impacts of long working hours, said the study's findings constitute "important new evidence" that could help better understand how long working hours "radically" impact workers' physical health.

Pega added that the research supports his previous findings that "long working hours contribute the largest burden of disease of all occupational risk factors identified so far."

"Governments, employers, and workers can all take actions to protect workers' health from long working hours," Pega added.

Jonny Gifford, principal research fellow at the Institute for Employment Studies in England, said that the research "confirms some physiological reasons that working long hours affects our wellbeing."

"The use of brain scanning equipment to give neurological explanations gives powerful new evidence linking overwork with structural changes in parts of the brain involved in executive function and emotional regulation," he said.

"It's a small study of 110 healthcare workers in Korea, but because it is based on robust neurological measures and concerns fundamental mechanisms (overwork and fatigue) that can affect anyone, the central findings are widely relevant," Gifford added.