Researchers at Cedars-Sinai Medical Center in the US have established a link between bacterium in the retina and cognitive decline and Alzheimer’s disease.
Chlamydia pneumoniae, commonly found in the respiratory system, has previously been found in the brains of Alzheimer’s sufferers.
The study, published in Nature Communications, cemented the link between higher levels of the bacterium in the retina and people with the disease.
Researchers hope their work will help pave the way for fresh approaches to Alzheimer’s and cognitive decline.
“The eye is a surrogate for the brain, and this study shows that retinal bacterial infection and chronic inflammation can reflect brain pathology and predict disease status, supporting retinal imaging as a non-invasive way to identify people at risk for Alzheimer’s,” said neuroscientist Dr Maya Koronyo-Hamaoui.
The researchers analysed eye and brain tissue from 104 people with varying degrees of cognitive impairment after death. Some had no reported problems.
They found a clear association between the presence of the bacterium in the retina and Alzheimer’s, but the differences between people without cognitive impairment and those with some impairment were much less clear-cut.
They followed this up with tests using lab-grown neurons and animal models, which helped show that infections with the bacterium led to more inflammation, cognitive decline and nerve cell death.
“This discovery raises the possibility of targeting the infection-inflammation axis to treat Alzheimer’s,” said biomedical scientist Professor Timothy Crother.
