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A bacterium prevalent in sinus infections and pneumonia may aggravate Alzheimer’s disease, according to a recent study published in Nature Communications. 

The bacterium, Chlamydia pneumoniae, was found in the eyes of deceased patients with Alzheimer’s disease, according to researchers from Cedars-Sinai’s Health Sciences University in California.

“The retina is directly connected with the brain. It’s a developmental extension of the brain,” lead researcher Maya Koronyo-Hamaoui, PhD, professor of neurosurgery, neurology and biomedical sciences at Cedars-Sinai Health Sciences University, told Fox News Digital.

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Eye-brain link

The study showed that Chlamydia pneumoniae could reach the retinal tissue that lines the back of the eye and linger for several years, creating an inflammatory response potentially linked to the death of nerve cells. This could contribute to cognitive decline and could worsen Alzheimer’s disease symptoms. 

The findings point to potential therapies for Alzheimer’s disease that would target inflammation and provide antibiotic treatment in the early stages of infection, according to Koronyo-Hamaoui.

“One hope of this study is that when people do present with some [symptoms of] pneumonia or atypical pneumonia or some respiratory infection, doctors should consider testing specifically for Chlamydia pneumoniae, and then give them the specific antibiotic,” the researcher said.

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The infection can be identified through laboratory testing, including PCR (polymerase chain reaction), blood tests, or cultures that allow live organisms to grow for analysis.

Inside the study

The researchers examined retinal tissue samples from over 100 deceased individuals who fell into three groups: those who had Alzheimer’s disease, those who had some cognitive deficit or those who did not have the disease. 

They analyzed proteins, conducted genetic testing and used advanced imaging techniques on the samples. Those with Alzheimer’s disease had higher levels of the bacterium in their brains and retinal tissue compared to those who had normal cognition, the release stated.

Genetic risk

Higher levels of chlamydia pneumonia were found in those who carried the gene variant APOE4, which is an associated risk factor for Alzheimer’s disease, Koronyo-Hamaoui added. The bacterium was also associated with more severe cognition decline.  

The Cedars-Sinai team also looked at human neurons and lab mice with Alzheimer’s disease, finding that Chlamydia pneumoniae was linked to increased inflammation, nerve cell death and cognitive decline, further suggesting that it may play a role in accelerating the disease. 

The infection also prompted production of amyloid-beta, which is a protein known to accumulate in the brains of those with Alzheimer’s, Koronyo-Hamaoui said.

While the study points toward using the retina as a way to diagnose and monitor the disease, the researcher acknowledged that more research is needed to confirm these findings.

Experts urge caution

Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau on Long Island, New York, was not involved with the study but called the findings “interesting.” 

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Glatt, who is also a spokesperson for the Infectious Diseases Society of America, emphasized that the findings only show an association and not causation, and that much more clinical research is needed.

“It does not mean infections cause Alzheimer’s or that people should worry about past respiratory illnesses.”

“Chlamydia pneumoniae is a very common respiratory pathogen that many people are exposed to throughout their lives,” he told Fox News Digital. “While the study identifies a link between this bacterium and neurodegeneration, a standard sinus infection does not mean a patient will develop Alzheimer’s.”

The key takeaway, according to Glatt, is that the study opens new doors for potential diagnostics and treatments, but is “not a reason for immediate alarm regarding common infections.”

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Dr. Sharon Fekrat, MD, a clinical spokesperson for the American Academy of Ophthalmology and a retina specialist at the Duke University School of Medicine in North Carolina, agreed that the findings could help researchers better understand how inflammation may drive disease progression and “could lead to new ways to detect or treat Alzheimer’s in the future.”

“This is early research suggesting that infection-related inflammation may worsen Alzheimer’s disease in people who are already vulnerable,” Fekrat, who also did not work on the study, told Fox News Digital. “It does not mean infections cause Alzheimer’s or that people should worry about past respiratory illnesses.”

What’s next

While some teams are developing and testing retinal imaging tools in living patients, those methods are not yet part of routine clinical screenings or diagnosis, Fekrat noted.

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For now, the best proven steps include following brain-healthy habits, such as managing cardiovascular risk factors, staying mentally and socially engaged, and seeking medical care for any cognitive symptoms, the expert added.

The temperature of the bedroom at night could affect heart health — particularly in older adults.

Heat places extra demands on the cardiovascular system, according to lead study author Dr. Fergus O’Connor from Griffith University in Queensland, Australia.

When the human body is exposed to heat, its reaction is to work harder to try and circulate blood to the skin surface for cooling, he noted.

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“However, when the heart works harder and for longer, it creates stress and limits our capacity to recover from the previous day’s heat exposure,” O’Connor stated in a press release.

Researchers aimed to understand how real-world bedroom temperatures affected older adults.

The team followed 47 adults living in southeast Queensland averaging 72 years of age.

While many sleep observations are conducted in special clinics, this was a “free-living” study, meaning the participants carried on with their normal activities and sleep schedules.

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Scientists monitored the participants throughout an entire Australian summer, from December to March. Each person wore a high-tech fitness tracker to monitor their heart rate from 9 p.m. to 7 a.m., according to the release.

Sensors were then placed directly in participants’ bedrooms to record the temperatures, monitoring over 14,000 nighttime hours of sleep in total.

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The temperature at which the heart began to show signs of disruption was a little more than 75 degrees Fahrenheit.

Between 75 and 79 degrees Fahrenheit, the odds of a “clinically relevant” drop in heart recovery rose by 40%, the researchers found.

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Between 79 and 82 degrees Fahrenheit, the odds doubled. Above 82, the risk was nearly triple compared to cooler rooms.

“For individuals aged 65 years and over, maintaining overnight bedroom temperatures at 24 C (75.2 F) reduced the likelihood of experiencing heightened stress responses during sleep,” O’Connor said.

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While the study shows a strong link between heat and heart stress, its observational design means that it doesn’t definitively prove heat is the only cause, the researchers acknowledged. 

As the study only focused on older adults in Australia, it may not apply to other populations.

“When the heart works harder and for longer, it creates stress and limits our capacity to recover from the previous day’s heat exposure.”

Also, while the wearable devices are advanced, they are not as precise as the medical-grade ECGs used in clinical settings.

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O’Connor emphasized a gap in temperature guidance — while there are guidelines for maximum daytime indoor temperature, there are no equivalent recommendations for nighttime conditions.

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The study was published in the journal BMC Medicine.