WEBDESK: Many people working 52+ hours per week report feeling exhausted and stressed. Recent research suggests this may reflect real changes in the brain. A new MRI study of Korean healthcare workers found that those clocking ≥52 hours weekly had significantly larger grey‐matter volumes in parts of the prefrontal cortex and insula – areas that govern attention, planning, decision-making and emotions.
Brain Regions Affected by Overwork: Studies highlight changes in:
- Prefrontal cortex (middle/superior frontal gyrus) – more grey matter, but potentially linked to fatigue in planning and memory.
- Insula – a region integrating emotion and self-awareness, also enlarged in overworked individuals.
- Other cognition/emotion areas (e.g. temporal lobes).
At the same time, stress from very long hours is known in other research to shrink some brain structures. For example, chronic stress (from any source) has been linked to hippocampal volume loss (the memory center) on the order of ~10–15%, and to reduced dendrites in prefrontal neurons. Animal studies show that severe repeated stress can shrink the hippocampus early on, leading to later memory deficits. In short, while overwork in the short term was associated with greater volume in some frontal areas, persistent stress is known to damage memory and emotion centers in the brain. More research (especially long-term imaging) is needed to see how overwork might eventually thin or alter these brain regions.
Cognitive and Emotional Effects
Working extremely long hours also affects thinking, memory and mood. In one large longitudinal study of 2,214 British civil servants, people who worked >55 hours/week did worse on cognitive tests than those working ≤40 hours. They had lower scores on vocabulary tests both initially and years later, and showed steeper declines in logical reasoning over time. In plain terms, chronic overtime was linked to poorer memory and decision-making in middle age.
Moreover, overwork is tied to mood and mental health. Employers and researchers note that people in high-overtime jobs report more fatigue, irritability and anxiety. In the Korean MRI study, the very brain regions that changed (insula and frontal lobes) are crucial for emotional regulation; stress in these areas could underlie feelings of burnout or mood swings. Separate data find that long work hours raise the risk of depression and anxiety.
Official Work-Hour Guidelines
Public health bodies warn against sustained overtime. The WHO and ILO classify working ≥55 hours/week as hazardous: one joint report found it increases stroke risk by ~35% and heart disease risk by ~17% compared to a standard 35–40 hour week. In fact, nearly 800,000 deaths worldwide per year were attributed to long hours (≥55) in 2016.
Traditionally, the ILO’s Hours of Work Convention (1919) set the standard workweek at 48 hours (8h/day) for industrial workers. Many modern labor laws cap 40–48 hours/week. In line with this, U.S. safety agencies (NIOSH/CDC) advise built-in rest: for example, responders should plan at least one full day off per week after consecutive shifts, and ensure 10+ hours off per 24-hour period to get enough sleep. In practice, experts urge limiting overtime and enforcing mandatory rest days to protect workers’ mental and physical health.
Key Takeaways:
Prolonged workweeks (>52–55h) are now linked to actual brain changes in areas for memory, planning and emotion. These changes may underlie the memory lapses, poor concentration and mood swings often reported by overworked people. To safeguard health, international guidelines generally recommend capping work around 40–48 hours and building in regular rest.
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