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Stress ‘eats away’ our brain’s cognitive defenses

Stress is known to negatively impact the human body, but a new study from the Karolinska Institutet reveals its significant danger to the brain. The research shows that stress can erode cognitive defenses, increasing dementia risk.

Stress is a cognitive thief 

The experts explored how daily activities and cognitive health are interconnected. Engaging in mentally stimulating activities, such as education, complex jobs, physical exercise, and social interactions, builds a “cognitive reserve,” which acts as a buffer against dementia symptoms. 

However, the researchers add a critical twist: stress can undermine these benefits. High or persistent stress levels act as a cognitive thief, reducing the mental resilience built through these activities.

“Different stress management strategies could be a good complement to existing lifestyle interventions in Alzheimer’s prevention,” said lead author Manasa Shanta Yerramalla, a researcher at Karolinska.

Life experiences build a cognitive reserve 

The discovery process began in the late 1980s when researchers noticed that some individuals showed no symptoms of dementia despite having brain changes consistent with Alzheimer’s. 

This led to the concept of “cognitive reserve,” suggesting that certain life experiences and behaviors build a mental resilience that protects against cognitive decline. 

Each mentally stimulating activity adds a layer of protection, helping maintain normal cognitive function even as Alzheimer’s disease progresses.

Measuring the impact of stress

The researchers enrolled 113 participants from a memory clinic to study the relationship between cognitive reserve, cognition, and Alzheimer’s biomarkers. 

They also examined the impact of stress, measuring physiological stress (cortisol levels in saliva) and psychological stress (self-reported stress). Cortisol, often called the “stress hormone,” rises under pressure and acts as the body’s alarm system. 

Stress weakens our brain’s defenses 

The study revealed that while greater cognitive reserve improved cognition, higher cortisol levels weakened this beneficial relationship, indicating that stress erodes the protective layers of the mental fortress.

This discovery suggests that stress-reducing techniques like mindfulness exercises and meditation, which lower cortisol levels, could be powerful additions to existing lifestyle interventions. Building cognitive reserve through mental activities and managing stress could maintain brain defenses.

“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,” Yerramalla said.

Connection between sleep and cognitive reserve 

The researchers also considered the impact of stress on sleep, which affects cognition. Although the study factored in sleep medications, more research is needed to understand how poor sleep damages cognitive reserve.

The study opens new avenues for Alzheimer’s prevention by integrating stress management with lifestyle interventions. Understanding how stress affects cognition can lead to better strategies for maintaining cognitive health and preventing dementia. 

The scientists plan to continue studying the association between stress, sleep disorders, and cognitive reserve in memory clinic patients to develop effective interventions for Alzheimer’s prevention.

Impacts of stress on the brain

Stress can significantly impact the brain, affecting both its structure and function in multiple ways. 

Brain shrinkage 

Chronic stress can lead to the shrinkage of the hippocampus, the part of the brain crucial for memory and learning, while also enlarging the amygdala, which can make the brain more receptive to stress. 

This change not only affects memory but also increases emotional reactions and anxiety.

Neurochemical effects

Neurochemically, stress elevates levels of the hormone cortisol, which can disrupt synapse regulation, leading to a decrease in the brain’s ability to process information and cope with stress in the future. 

It also hampers the production of new neurons and can contribute to mental health disorders like depression and anxiety over time.

Brain connectivity 

Furthermore, stress affects the brain’s connectivity; it can weaken the connections between neurons in areas responsible for decision making and self-control, making it more difficult to make rational decisions and manage impulses. 

This condition underscores the importance of managing stress through strategies such as mindfulness, exercise, and adequate sleep, which can help mitigate these negative effects on the brain.

The study is published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association


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