Chronic overwork may lead to changes in brain regions associated with emotion and cognition

Long working hours may alter the structure of the brain, particularly the areas associated with emotional regulation and executive function, such as working memory and problem solving, suggest the findings of preliminary research, published online in Occupational & Environmental Medicine.

Ultimately, overwork may induce neuroadaptive changes that might affect cognitive and emotional health, say the researchers.

Long working hours have been linked to heightened risks of cardiovascular disease, metabolic disorders, and mental health issues. And the International Labour Organisation (ILO) estimates that overwork kills more than 800,000 people every year, note the researchers.

While the behavioural and psychological consequences of overwork are reasonably well understood, the underlying neurological mechanisms and anatomical changes aren't, they add.

To explore this further, the researchers deployed structural brain volume analysis to compare the impact of overwork on specific brain regions in healthcare workers routinely clocking up long working hours, defined as 52 or more a week.

They drew on data from the Gachon Regional Occupational Cohort Study (GROCS) and from MRI scans carried out for a research project on the effects of working conditions on brain structure. 

Participants in GROCS were asked to have an additional MRI scan, and the final analysis included 110 people after excluding those with missing data or poor MRI image quality. Most were clinicians: 32 worked excessive weekly hours (28%); 78 worked standard hours.

Those putting in long working hours every week were significantly younger, had spent less time in work and were more highly educated than those clocking up standard hours. 

Differences in brain volume were assessed using voxel-based morphometry (VBM)---a neuroimaging technique that identifies and compares regional differences in levels of grey matter-and atlas-based analysis, which uses pre-defined references to identify and label structures in images like brain scans. 

Comparative analysis of the findings showed that people who worked 52 or more hours a week displayed significant changes in brain regions associated with executive function and emotional regulation, unlike participants who worked standard hours every week. 

For example, atlas-based analysis revealed a 19% increase in the volume of the middle frontal gyrus among those clocking up long working hours compared with those working standard hours. 

This part of the brain has a major role in various cognitive functions, particularly in the frontal lobe. It's involved in attention, working memory, and language-related processing. 

VBM showed peak increases in 17 regions, including the middle frontal gyrus, the superior frontal gyrus, which is involved in attention, planning, and decision-making, and the insula. 

The insula has a key role in integrating sensory, motor, and autonomic feedback from the body. It's involved in emotional processing, self-awareness, and understanding social context.

This is a small observational snapshot study, and as such, no firm conclusions can be drawn about cause and effect. And the researchers acknowledge that in the absence of long term data, it's unclear whether these structural changes are a consequence of overwork or a predisposing factor.

But they nevertheless point out: "While the results should be interpreted cautiously due to the exploratory nature of this pilot study, they represent a meaningful first step in understanding the relationship between overwork and brain health."

They add: "Notably, the increased brain volumes observed in overworked individuals may reflect neuroadaptive responses to chronic occupational stress, although the exact mechanisms remain speculative."

They continue: "The observed changes in brain volume may provide a biological basis for the cognitive and emotional challenges often reported in overworked individuals. Future longitudinal and multi-modal neuroimaging studies are warranted to confirm these findings and elucidate the underlying mechanisms." 

And they conclude: "The results underscore the importance of addressing overwork as an occupational health concern and highlight the need for workplace policies that mitigate excessive working hours."