Night owls in 9-to-5 jobs may experience more brain fog over time: Here’s what science suggests to protect your mind

A decade-long study reveals night owls experience greater cognitive decline than early risers, especially among the highly educated.

Are you someone who thrives after sunset, bingeing shows or getting work done when the world sleeps? Well, science might have a wake-up call for you. A recent comprehensive 10-year study involving nearly 24,000 adults has revealed a concerning link between being a night owl and cognitive decline, but with an unexpected twist.

Researchers at the University of Groningen tracked participants over a decade and found that night owls faced notably greater cognitive decline compared to early risers. The surprising detail? This pattern didn’t appear in individuals with lower levels of education, no matter their sleep habits.

How does being a night owl affect your brain over time

Among college-educated adults, every hour shift toward a night owl schedule led to a 0.80-point drop in cognitive scores over 10 years, a noticeable dip in mental sharpness for extremely late sleepers. Your chronotype, or natural sleep-wake preference, is guided by your circadian rhythm, the body’s internal clock. While around 20 percent of adults lean toward late nights in midlife, only 7 percent are true early birds.

A study reveals that night owls face cognitive decline, particularly in highly educated individuals. (Freepik)

The link to education seems to boil down to job flexibility. Highly educated professionals often have rigid 9-to-5 schedules, leaving little room for natural sleep preferences. In contrast, people with less formal education often work varied hours that may align better with their body clocks.

When your job forces early wake-ups against your natural rhythm, it creates “social jet lag”, a kind of ongoing biological mismatch. Night owls with strict schedules may feel this more acutely. “Children are morning people, but that shifts in puberty,” explains lead author Ana Wenzler. “Most revert to being morning types by 40, but not everyone. Evening people deviate from that norm.”

Why do sleep and smoking matter

Published in The Journal of Prevention of Alzheimer’s Disease, the study pointed to two main drivers of cognitive decline in night owls: poor sleep and smoking. Among highly educated participants, these explained about a third of the link to brain fog.

Night owls often had worse sleep quality, likely due to staying up late but waking early for work, leading to chronic sleep deprivation, which affects the brain’s ability to clear harmful proteins tied to Alzheimer’s. Surprisingly, smoking accounted for about 19 percent of the decline. Night owls were more likely to smoke, possibly to counter the effects of their disrupted sleep schedules. Alcohol use and physical activity didn’t play a significant role despite differences in habits.

How can night owls protect their minds

Approximately one in five American adults naturally prefer late sleep schedules, which means millions, particularly professionals with early-morning routines, could be affected. The study assessed cognitive decline through tests focused on executive function and problem-solving, both essential for adapting to new situations and managing everyday tasks.

The study reveals that screen activities post-bedtime harm sleep more than pre-bedtime usage. (Freepik)

While the researchers stop short of directly linking this decline to dementia, any measurable drop in cognitive function over a decade is concerning. That said, these findings may open the door to preventive strategies. Flexible work hours could be especially beneficial for highly educated night owls. Allowing later start times for those whose biological clocks favour evening hours may help protect long-term brain health.

Additionally, programs aimed at improving sleep quality and supporting smoking cessation could play a key role. Since these two factors accounted for 25 percent of the cognitive decline observed, addressing them may significantly reduce risk.

Previous research has consistently emphasised the critical role of sleep in maintaining optimal brain function. This study reinforces the idea that our natural sleep preferences may carry real cognitive consequences, particularly when they clash with daily schedules. For those navigating structured early-morning environments despite an evening chronotype, the goal should not be to override biology but to work with it or minimise the long-term strain of resisting it.