S2E30. Can Vaccinations Prevent Dementia?

An interesting study published last month reported a 40% reduction in the risk of getting Alzheimer’s dementia for people 65 and over who regularly receive flu shots. What’s more, the earlier you start getting your annual shot (i.e., before the age of 60), the greater the protective benefit.

That’s a fascinating and wonderful finding, but it begs the question: why? Why would getting a vaccine that trains your immune system to fight off the flu virus protect you from developing dementia? Especially when the dementing process has probably been active in your brain for a number of years?

Immunology is a field of science that is way out of my comfort zone, but I read some journal articles anyway to see if I could make any sense of it. So please take what I say with a few grains of salt, as I may be wildly misinterpreting the data.

It seems that flu vaccine isn’t the only vaccine that is protective against dementia. Tuberculosis, tetanus, pneumonia, and herpes vaccines are also beneficial…but direct links between the viruses involved and dementia have not been found.

Perhaps, I theorized, the vaccines prevent you from getting the targeted illnesses which, in turn, means that you have fewer incidents of extreme immune-response inflammation which, in turn, minimize your brain’s production of beta amyloid and tau proteins. Sounds reasonable, right? But this study controlled for the number of times people actually got the flu and there was no correlation.

I thought, maybe, that people who get their annual flu shots are, in general, more health conscious and engage in other lifestyle habits that are protective (e.g., diet and exercise). But that didn’t turn out to be a factor, either.

The study’s authors suggested a couple of possible explanations, all of which require a significant amount of further research before any causal conclusions can be drawn. And—to be honest—in some instances, I had trouble understanding what they were proposing. The one hypothesis that made the most sense to me posited that vaccinations for specific viruses also have a general effect on one’s immune system, modifying it in a way that enhances its ability to deal with the chemical compounds that really are at the root of dementia, whether they be beta amyloid and tau or some other as yet unidentified compounds.

If this turns out to be the case, then it’s possible that the COVID pandemic has a silver lining for all of us who faithfully received our two shots and follow-up boosters. We should know in about 5-10 years.

Given these findings, it’s not surprising that there are trials currently underway to test vaccines specifically designed to train your immune system to recognize and attack beta amyloid plaques. As I’m not a big fan of that theory, I have my doubts that it will actually work as intended, but it might be beneficial because of the general effect that vaccines have on the immune system. I wonder: How will the researches tell the difference if, indeed, a significant effect is found?

Another thing about this recent study that caught my attention was the finding that it reduced the risk of developing Alzheimer’s by 40%. Other studies have shown that exercise reduces your risk by 30-45%. Adherence to the Mediterranean Diet has been shown to reduce one’s risk by somewhere between 30-72%. And don’t forget the benefits of regular cognitive challenge, good sleep hygiene and social engagement. Yet most experts say that you can reduce your risk of dementia by only 40-50% by implementing all of these strategies. How can that be? Why isn’t the protection rate up around 75% or more if you implement all of the strategies the research has identified?

There are some studies that tried to simultaneously measure the impact of two or more of these factors and they show the effects to be independent of each other…yet the total effect doesn’t seem to increase as you add more levels of protection. That seems odd to me.

Is it possible that each factor impacts the same unknown dynamic that causes dementia but by different means? Or are there a variety of different etiologies for the cluster of symptoms we have defined as ‘dementia’ and each of these factors are protective against some but not all of them? Do some strategies go after the root cause while others build resilience to compensate for damage that occurs elsewhere?

It’s mind boggling (no pun intended).

I just hope my brain is still in good enough shape to appreciate it when the research finally reveals the answers. In the meantime, I’ll faithfully show up for every vaccination that Medicare and my insurance cover!

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