Study links multiple viral infections to a higher risk

A neurodegenerative disease affects the body’s central nervous system, including the brain. Such conditions can impair certain bodily functions such as movement, balance, speaking, thinking and memory.

Types of neurodegenerative diseases include:

There is currently no cure for neurodegenerative diseases. Doctors advise people to change certain ones risk factors for these conditions to prevent or slow their progression. And many have medication available to assist in treatment and management of disease symptoms.

For this study, the researchers first searched about 300,000 medical records in the Finnish biobank FinnGenlooking for people suffering from one of six neurodegenerative diseases – Alzheimer’s disease, ALS, generalized dementia, multiple sclerosis, Parkinson’s disease or vascular dementia.

Scientists analyzed the limited records to determine if any of these individuals had also been screened for a viral infection at a hospital.

In this first phase of research, the research team identified 45 significant associations between a diagnosis of a neurodegenerative disease and a previous viral infection.

The team then narrowed those assignments down to 22 after conducting a second medical record search of the 500,000 medical records in the UK Biobank.

Of the six selected neurodegenerative diseases, the researchers reported that generalized dementia had the most associations with viral exposure. They found links between dementia and more than six different viral diseases – viral encephalitisviral warts, all influenza, influenza and pneumonia, viral pneumonia and other viral diseases.

Scientists reported that people with viral encephalitis were at least 20 times more likely to be diagnosed with Alzheimer’s than people who didn’t have the virus. And the researchers found that severe cases of influenza were associated with a wide range of risks for neurodegenerative diseases.

“Over the years, several laboratory experiments have indicated that viruses may be a risk factor for neurodegenerative diseases,” Dr. Mike Nalls, leader of the Advanced Analytics Expert Group at the NIH Center for Alzheimer’s and Related Dementias (CARD) and senior author of this study Medical news today.

“What struck us is that we were able [to] Get similar results by data mining medical records,” he said.

While this study examines the potential associations between viral exposure and the risk of neurodegenerative diseases, the researchers caution that a causal relationship cannot yet be confirmed.

“At this point, we’re not addressing the mechanistic link, we’re just showing an association – there’s a lot more work to be done,” warned Dr. nalls “The results of this study provide researchers with several new critical pieces of the puzzle about neurodegenerative diseases.”

“In the future, we plan to use the latest data science tools to not only find more pieces, but also to help researchers understand how those pieces, including genes and other risk factors, fit together,” he added .

dr Melita Petrossian, a neurologist and director of the Pacific Movement Disorders Center at the Pacific Neuroscience Institute in Santa Monica, California, who was not involved in this study, commented on the results for MNT:

“The way I think about this type of viral exposure is that it’s part of the puzzle and suggests that whatever the driving forces behind these neurodegenerative diseases, including Alzheimer’s and Parkinson’s, there is nothing that makes anyone think it to get those terms.”

“It suggests that there are factors – in this case we are talking specifically about environmental factors, but we know from other studies that there are also genetic factors – that play a role in the development of these neurodegenerative diseases and those processes that take decades before the disease manifests itself,” she added.

Vaccines are currently available for various viral diseases. How could these findings change the way doctors advise patients about certain vaccines?

For example a previous study linked the shingles vaccine to a reduced risk of dementia. And other researchers link the influenza vaccine to a reduced risk of Alzheimer’s.

“The obvious thought would be that if you can reduce the viral load, you could reduce the inflammatory process of the virus, you could reduce the systemic inflammatory processes that can eventually be associated with neurodegeneration over the years,” explained Dr. Petrosian.

“Ideally, people who are choosing vaccines should think about having another tool in their pocket to reduce the risk of neurodegenerative diseases,” she said.

She added that it is sometimes difficult for patients to understand that vaccines have not only short-term effects but potentially long-term effects as well.

“It’s something that doesn’t come to mind when people think about their vaccination decisions, but ideally it would be really great to see people have a greater motivation to get vaccinated to protect themselves against the potential risk of getting vaccinated neurodegenerative disease, but also to protect the community,” noted Dr. Petrosian.

MNT also spoke to dr. Clifford Segil, a neurologist at Providence Saint John Health Center in Santa Monica, California, who was also not involved in the study, had a different take on the results.

“I will use your exact words – no causal relationship was found in this study, there are significant associations, [and] Medical decisions should not be based on associations of meaning,” he warned.

dr Segil said certain viruses — like the herpes virus and West Nile virus — can cause confusion, which can later lead to memory loss.

“When these viruses cause encephalitis, people get confused,” he explained. “And later in life, people who have had encephalitis may have more memory loss. It is a stretch to say that a patient who has had viral encephalitis has Alzheimer’s dementia. If they are confused later in life, the confusion comes from viral encephalitis, not Alzheimer’s dementia.”

For the next steps in this research, Dr. Segil, he’d like to see a correlation with neuroimaging. “I would like to see the neuroimaging results to correlate this if any of these patients have abnormalities from any of these viruses,” he added.