Stress literally eats away at your brain’s cognitive reserve

SOLNA, Sweden — It’s no secret that stress can have a negative effect on the human body. However, a new study is revealing just how dangerous stress can be for the human brain. Publishing their work in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, Swedish researchers say stress can actually chip away at your brain’s cognitive defenses — putting you at higher risk for dementia.

The findings, in a nutshell

This groundbreaking study from Karolinska Institutet has uncovered a fascinating interplay between our daily activities and cognitive health. Researchers have long believed that engaging in mentally stimulating activities, like going to college, tackling complex jobs, staying physically active, and maintaining a rich social life, can help build a “cognitive reserve.”

This reserve acts as a mental buffer, potentially protecting our brains from the symptoms of dementia, even when physical signs of the disease are present. However, this new research adds a critical twist to our understanding: stress. While these brain-boosting activities can enhance cognition in memory clinic patients, high or persistent stress levels can undermine these benefits.

It’s as if stress acts as a cognitive thief, robbing us of the mental resilience we’ve worked hard to build. This finding is particularly significant as stress is known to reduce social interactions, hinder our ability to engage in leisure activities, and even increase the risk of dementia.

“Different stress management strategies could be a good complement to existing lifestyle interventions in Alzheimer’s prevention,” says the study’s lead author Manasa Shanta Yerramalla, a researcher in the Department of Neurobiology, Care Sciences and Society at the Karolinska Institutet, in a media release.

While brain-boosting activities can enhance cognition, high or persistent stress levels can undermine these benefits. (Photo by Kampus Production on Pexels)

How did researchers make this discovery?

The journey to this discovery began in the late 1980s when researchers made a puzzling observation. Some individuals who showed no apparent symptoms of dementia during their lifetime had brain changes consistent with advanced Alzheimer’s disease. This led to a new line of dementia-related questioning: If their brains showed signs of the disease, why weren’t they experiencing symptoms?

The investigation led to the concept of “cognitive reserve” — the idea that certain life experiences and behaviors can build up a mental resilience that protects against cognitive decline. Think of it like building a strong, multi-layered fortress in your brain. Each mentally stimulating activity — whether it’s studying for a degree, solving complex problems at work, or engaging in lively discussions with friends — adds another layer of protection. Even if Alzheimer’s disease starts to breach the outer walls, the inner layers can help maintain normal cognitive function.

Fast forward to today, and researchers at Karolinska Institutet decided to dig deeper. They gathered 113 participants from the memory clinic at Karolinska University Hospital in Sweden. Their goal was to examine how cognitive reserve relates to cognition and biomarkers for Alzheimer’s disease. However, they added a unique twist to their study. The team also looked at how stress might affect this relationship.

Yerramalla’s team measured two types of stress: physiological stress (using cortisol levels in saliva) and psychological stress (how stressed participants felt). Cortisol is often called the “stress hormone” because its levels rise when we’re under pressure. Think of cortisol as your body’s built-in alarm system. The results show that while greater cognitive reserve did improve cognition, as expected, higher cortisol levels seemed to weaken this beneficial relationship. It’s as if stress was slowly eroding the protective layers of their mental fortress.

This discovery opens up exciting new avenues for Alzheimer’s prevention. The researchers suggest that stress-reducing techniques like mindfulness exercises and meditation, which can lower cortisol levels, might be a powerful addition to existing lifestyle interventions. Just as we build our cognitive reserve through mental workouts, we might also need to incorporate stress management to maintain our brain’s defenses.

The team notes that since stress disrupts sleep, which then disrupts cognition, this study did factor in the use of sleep medications by the participants. However, there is still more work to do to identify how exactly poor sleep damages the cognitive reserve.

“These results might have clinical implications as an expanding body of research suggests that mindfulness exercises and meditation may reduce cortisol levels and improve cognition,” Dr. Yerramalla, adds. “We will continue to study the association between stress and sleeping disorders and how it affects the cognitive reserve in memory clinic patients.”

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