Viruses linked to later dementia

A very large new study (n = 335,000, Finland) showed an association between people who had been hospitalized with viral illness and later neurodegenerative disease, including dementia (often within a year but up to 15 years later). The study results were replicated with another very large data set (n = 106,000, U.K.).

Dementia had the most associations, with links to six different virus exposures: viral encephalitis, viral warts, other viral diseases, all influenza, influenza and pneumonia, or viral pneumonia.

The highest hazard ratio was seen for the relationship between viral encephalitis and Alzheimer’s: 30.72 for the discovery (Finnish) cohort, with an odds ratio of 22.06 for the replication (U.K.) cohort.

“To place this in context, we see in FinnGen, 24 of 406 viral encephalitis cases went on to develop Alzheimer’s disease (5.9%); this is higher than the general prevalence of Alzheimer’s disease in the same population at less than 3%.” The Hazard Ratio (HR) compares the probability of the affected group compared with the control group. The change may be significant even if the absolute numbers are low.

“The overwhelming majority of replicated associations include viruses commonly considered neurotrophic (81%), which means they can invade the central nervous system through peripheral nerves or by crossing the blood-brain barrier,” the researchers observed. “This suggests that these viruses may increase neurodegenerative disease risk by lowering cognitive reserve (resilience to neurodegeneration and the ability to carry out complex mental tasks) by contributing to inflammation in the brain.”

The study did not include Covid.

These are nasty viral diseases. They can kill even aside from the new discovery about later neurodegeneration. I get my flu shot every year and have also had the multi-valent pneumonia vaccines. No point taking a chance with this.

Wendy

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Thanks for the posting, Wendy. It’s an interesting discovery but so many questions remain to be answered.

  1. What causes the damage? The virus itself? The viral illness? Or some treatment for it?

  2. How effective is a vaccine in preventing damage?

  3. Only the sickest patients go to the hospital. You wonder how many are tested for presence of the virus. After Covid we have to ask which one?

  4. What about all the people out there infected with the virus but with minor illness or even no symptoms.

Lots more study seems to be needed for each one. May well take decades to get the answers we need.

And then we are reminded of ulcers. Some studies do turn out to reveal effective treatments.

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So, are we going to stop berating everybody everywhere over every single disease, condition, and misfortune being the “obvious” result of some sort of evil lifestyle choice? Especially what they eat? No matter what they eat ?

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Reading that I was just about to say this maybe something mechanical but something physiological is more appropriate. A bacteria in the mouth also has such results when found in larger quantities with age in the brain.

One of the best ways to mitigate inflammation in the body and mind MIGHT be meditation.

@pauleckler

  • What causes the damage? The virus itself? The viral illness? Or some treatment for it?
    Some viruses infect the brain and damage it directly (viral encephalitis). Others may penetrate the blood-brain barrier but not necessarily attack brain cells directly. The researchers hypothesized that such a virus may cause inflammation in the brain which could damage neurons. We know from Covid that inflammation can cause even worse damage than the direct viral attack.

  • How effective is a vaccine in preventing damage?
    If the vaccine activates the immune system, which then kills the virus before it can replicate in the body and spread to the brain, the vaccine would be effective in preventing damage.

  • Only the sickest patients go to the hospital. You wonder how many are tested for presence of the virus. After Covid we have to ask which one?
    Viruses are usually diagnosed by their symptoms, almost never by testing. Covid was a rarity in the testing process. But doctors have been diagnosing flu, viral pneumonia and encephalitis for many years without tests.

  • What about all the people out there infected with the virus but with minor illness?
    The researchers pointed out that this is a weakness in their study. They had to get records from the national health service that they could definitely say had the virus. They decided to focus on the hospitalizations because those all had a firm diagnosis. There’s no way to know whether a minor illness would cause a problem, they recognized that.

Wendy

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