A common type of irritating eye bacteria can linger in the body for many years after your symptoms have lifted, potentially contributing to a devastating cognitive decline
Symptoms of this everday bacteria can linger for years, with potentially tragic consequences (Stock Photo)(Image: Getty Images)
An everyday eye bacteria has been linked to cognitive decline, including Alzheimer’s disease and other forms of dementia.
This extremely common bug, known as Chlamydia pneumoniae, is believed to infect as many as 80 per cent of adults at some point in their lifetimes, and for many, the symptoms may be very mild indeed, leaving sufferers with an easy-to-ignore sore throat or sleepiness. But it’s feared this irritating infection, found in retinal tissue at the back of the eye, could have a far more serious and long-lasting impact on the body, where it could linger for many years, potentially contributing to the life-altering destruction of a person’s cognitive health.
This is as per a team of researchers from Cedars-Sinai Health Sciences University in Los Angeles, who have determined a correlation between higher levels of this pathogen, advanced degeneration in those with Alzheimer’s disease. Although this doesn’t prove a definite causation, the findings certainly contribute towards a growing body of evidence which suggests chronic infections can be a factor in neurodegenerative diseases over time.
Professor Maya Koronyo-Hamaoui, the lead author of this study, explained: “Seeing Chlamydia pneumoniae consistently across human tissues, cell cultures and animal models allowed us to identify a previously unrecognised link between bacterial infection, inflammation and neurodegeneration. 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 noninvasive way to identify people at risk for Alzheimer’s.”
For this study, the findings of which have been published in the science journal Nature, the team analysed eye and brain tissue from 104 people after they’d already died. Some had lived with Alzheimer’s disease, and others had mild cognitive impairment (MCI), while the rest hadn’t reported any cognitive issues. A clear association between the presence of C. pneumoniae in the eye and brain and having an Alzheimer’s diagnosis, while higher levels of the bacterium in tissue were connected to more serious cognitive decline.
Professor Koronyo-Hamaoui concluded: “Seeing Chlamydia pneumoniae consistently across human tissues, cell cultures, and animal models allowed us to identify a previously unrecognised link between bacterial infection, inflammation, and neurodegeneration.” It’s now hoped that these findings could potentially one day contribute to targeted treatment for those with Alzheimer’s disease, a progressive condition which could affect more than two million people in the UK alone, as per figures provided by the Alzheimer’s Society. A leading cause of death, especially for women, it’s estimated that one in three people born today will develop Alzheimer’s within their lifetime.
This comes as European surveillance data suggests a sharp surge of C. pneumoniae in 2024, soaring from approximately five cases per 1,000 tests to nearly 17 per 1,000 within the space of just one year. While the cause of this isn’t yet understood, some scientists have suggested that the lack of exposure to everyday bacteria during the Coronavirus lockdown left people more vulnerable once they were allowed to mingle once more, creating what has been described as an ‘immunity debt’, in journals such as the National Library of Medicine.
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