According to a study published in the journal Nature Communications, Chlamydia pneumoniae—a bacterium typically responsible for pneumonia and sinusitis—may persist in the human eye and brain for years, significantly accelerating the development of Alzheimer’s disease.
The study reveals that this bacterium reaches the retina, where it triggers an immune response and chronic inflammation. Researchers explain that the eye acts as a physical extension of the brain. Therefore, detecting bacterial infection and inflammation in the retina allows scientists to predict pathological processes occurring in the brain through non-invasive methods, such as eye scans.
By conducting an in-depth analysis of tissues from 104 individuals, scientists identified a direct link between bacterial infection and neurodegeneration:
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Concentrations of Chlamydia pneumoniae were significantly higher in the retina and brain of Alzheimer’s patients.
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The increase in bacterial load correlates proportionally with the severity of cognitive decline.
The research also highlights a significant genetic component. High levels of infection are particularly prevalent in individuals carrying the APOE4 gene, suggesting that this gene plays a role in the body’s vulnerability to the bacterium.
Furthermore, the infection was found to provoke the accumulation of amyloid-beta, a pathological protein that accelerates the death of nerve cells in the brain.
This discovery opens entirely new possibilities for intervention. Scientists suggest that by targeting these factors—using early antibiotic therapy and anti-inflammatory treatments—it may become possible to delay the progression of the disease.
