Infections and Brain Atrophy: 5 Shocking Risks You Need to Know

A Story by Aman Gandhi.

4 months ago

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Infections and Brain Atrophy: How Immune Responses Influence Dementia Risk

Infections and brain atrophy are closely linked, with recent research revealing how past infections can impact brain volume and dementia risk. Learn about the latest study’s findings on immune proteins and cognitive decline.

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Infections and Brain Atrophy: How Immune Responses Influence Dementia Risk

Infections and brain atrophy have become a critical focus in recent research, shedding light on how past infections might impact brain health and increase the risk of dementia. A recent study published in Nature Aging explores this connection, revealing how changes in immune proteins due to infections can influence brain volume and cognitive decline.

Study Overview

The study aimed to understand the relationship between past infections and brain volume changes, focusing on specific immune proteins that could predict which brain regions are vulnerable to infection-related atrophy. Researchers used data from the Baltimore Longitudinal Study of Aging (BLSA), which included 982 participants averaging 65.4 years old. The data comprised MRI scans and blood samples, offering insights into how infections might affect brain health over time.

Link Between Infections and Brain Volume Loss

Infections and brain atrophy are linked in several ways. The study found that certain infections, such as influenza, human herpesvirus infections, and various respiratory and skin infections, were associated with increased brain volume loss, particularly in the temporal grey and white matter regions.

However, it’s important to note that after adjusting for multiple comparisons, these associations did not remain statistically significant. This means that while the initial findings suggest a connection, more research is needed to confirm these results.

Specific Brain Regions Affected

The impact of infections on different brain regions varied:

Influenza: This infection was associated with reduced brain volume in the occipital and temporal lobe grey matter.
Herpetic Infections: These were linked to decreased white matter volume specifically in the temporal lobe.
Miscellaneous Viral Infections: These infections primarily affected grey matter.
Upper and Lower Respiratory Tract Infections: These were associated with brain volume loss in both grey and white matter, though the specific patterns differed by infection type.

These findings suggest that different types of infections might influence brain atrophy in distinct ways, affecting specific brain regions.

Infections and Dementia Risk

The study also explored how infections relate to the risk of developing dementia. Researchers found that infections were associated with an increased risk of all-cause dementia. In particular, the risk was highest for vascular dementia (VaD), which aligns with previous research indicating that post-infection immune changes might contribute more significantly to cerebrovascular problems.

Five infections were associated with an elevated risk of VaD, while four infections were linked to Alzheimer’s disease (AD). These associations underscore the potential role of infections in dementia risk, highlighting the need for further investigation into how immune responses to infections might influence long-term cognitive health.

Immune Proteins and Brain Atrophy

Infections and brain atrophy are influenced by changes in immune proteins. The study identified 260 proteins associated with at least one infection. Out of these, 35 proteins were linked to changes in brain volume. These proteins were categorized as either protective or pathogenic based on their effects on brain volume.

Protective Proteins: These proteins were found to be reduced in individuals with a history of infections. Ten protective proteins were associated with preserved cognitive abilities, such as verbal memory and visuospatial performance.
Pathogenic Proteins: These were increased in individuals with infections and were linked to cognitive decline. Four pathogenic proteins were associated with rapid reductions in cognitive performance.

Interestingly, one pathogenic protein, CD27, was unexpectedly linked to preserved visuospatial abilities, indicating the complexity of these immune-brain interactions.

Genetic Associations

The study also examined whether genetic variants affecting immune protein levels were related to brain volume changes. They found that some genetic variants linked to lower levels of pathogenic proteins were associated with preserved brain volumes, even in regions prone to atrophy. However, not all genetic variants had protective effects; some variants that reduced pathogenic protein levels were paradoxically associated with increased brain volume loss.

Conclusions and Implications

Infections and brain atrophy are intertwined, with certain infections potentially contributing to brain atrophy and increased dementia risk. The study highlights how different infections might affect brain regions differently and emphasizes the role of immune proteins in these processes. While some associations did not hold up after multiple testing corrections, the overall pattern suggests a meaningful link between infections and neurodegeneration.

Identifying the 35 immunologically relevant plasma proteins that change after infection provides new insights into how infections might contribute to brain atrophy and cognitive decline. These findings support the need for further research to fully understand these complex relationships and their implications for dementia prevention and treatment.

As researchers continue to explore these connections, understanding how infections influence brain health through immune responses will be crucial for developing strategies to mitigate dementia risk and improve cognitive outcomes.