There are adjuvants in the vaccine. Have they ruled out that one or more of those is responsible for the effect?
Contrary to the comments from some posters, this study is certainly evidence that a virus causes dementia. It is not conclusive evidence, but using statistical evidence to prove a causal connection between the vaccine and dementia significantly increases the probability that a virus causes dementia, and that is the definition of evidence.
I just got the shingles vaccine a couple of weeks ago (I almost started a thread on getting that and Prevnar at the same time) and oof was it a painful reaction, not just massive arm soreness, but a hot lump at the vaccination site that persisted for about four days, and real tiredness. I can’t wait for the second dose in the fall!
Still, well worth it, and maybe even more so now!
I had the shingles vaccine in my left arm two weeks ago. At the same time I had the pneumococcal vaccine in my right. I forgot about them until I noticed the little round band-aids when I showered the next day. I had no reaction at all.
Bear in mind that in the history of Alzheimer’s research, there have been innumerable hopes raised over claims of discovery of the disorder’s cause(s), and supposed methods of prevention and treatment. Much of this research has gone nowhere.
That said, there is some evidence suggesting the possibility of herpesvirus (HSV-1) involvement, and that activation of dormant varicella-zoster virus (VZV, which causes chickenpox and shingles) may spur activation of HSV-1. There have also been at least a couple of studies linking shingles vaccination (mostly with the older, less effective vaccine Zostavax) to lower risk of dementia. Just to complicate things further, getting shingles doesn’t seem to increase one’s risk of Alzheimer’s.
The newer vaccine, Shingrix can have unpleasant side effects (Mrs. J. was down and out for a day after her first dose) but it’s very worthwhile if it spares you an attack of shingles, not to mention the possibility of avoiding dementia.
*note that the Guardian quoted a scientist whose work it suggested backed the vaccine/dementia prevention hypothesis, but linked to a study of his that didn’t involve the vaccine at all. Careless reporting.
This is what I was thinking. Who’s eligible for the vaccine might be a good cross-section of the population, but people still choose whether to get it, and that could be correlated with all sorts of things. Especially brain-related things. Even more especially since a lot of other behaviors have been shown to have correlation with eventual dementia or lack thereof.
This is the only theoretically possible confounding variable, but it seems implausible to me. What could a propensity to be vaccinated for shingles plausibly signify that would be correlated with a highly specific susceptibility to dementia, and that has never been picked up in any other study of dementia? It’s a large effect, and it has no effect on any other disease:
Besides preventing shingles and dementia, the herpes zoster vaccine had no effects on any other common causes of morbidity and mortality
Whereas, regarding prior studies:
To date, studies in cohort and electronic health record data on the relationship between vaccination receipt (with most studies focusing on influenza vaccination) and dementia have simply compared the occurrence of dementia among those who received a given vaccination versus those who did not… [but there are confounding variables] such as personal motivation or health literacy… vaccination receipt in these studies is not only associated with dementia but also a host of other health outcomes that are unlikely to be due to the vaccine
Just to add another data point re: the pain of the shingles vax, I had my first of two shots about two weeks ago, and had a day of… well, I wouldn’t even use the word “pain”, but rather, “discomfort”. My arm was sore, and ached; but nothing that a couple ibuprofen couldn’t handle. I, too, had hesitated about getting the shot, but it was no big deal, and I’m glad I finally did; doubly so, now.
Note also that there is an effect at p=0.02 (Fig 3, left side) when they compare eligible vs ineligible groups, without regard for whether eligible people chose to get the vaccine. Obviously the effect is smaller, since only around half of the eligible people got the vaccine. But at least some part of the effect is certainly attributable to the vaccine rather than just a confounding inclination to be vaccinated.
And as noted, I think the specificity of the protection against dementia but no other disease strongly suggests that at least part of the rest of the effect is also real.
I also hesitated to get the vaccine. It’s an unpleasant vaccine, like the covid vax or the tetanus vax. But it wasn’t horrible. Just a couple of days of aches and tiredness.
This is in support of the confounding effect of voluntary choice to be vaccinated, not against it. In particular,
the prior quote indicates that there is not that specificity.
Of course it is. Read it more carefully. That is a comment in the paper about PRIOR STUDIES, not this one. That’s the point - unlike prior studies which were poorly controlled for confounding variables and show nonspecific correlation with a broad range of health outcomes, in this study, the protective effect is highly specific:
Besides preventing shingles and dementia, the herpes zoster vaccine had no effects on any other common causes of morbidity and mortality.
Could the actual causal link be that avoiding long debilitating illnesses like shingles is good rather than it being caused by a specific virus? Based on everything we know long periods of being sick, with the associated lack of activity and social interactions (which is definitely the case with shingles cases in my experience) could definitely increase cognitive decline, regardless of the microbe which causes it
No, I don’t think that’s possible. The baseline incidence of shingles in this study is only around 5%, and this vaccine is as good as some for its intended purpose, reducing the incidence to around 3%. So there is a 50-fold dilution of second-order effects. Thus, if this were a second order effect consequent to shingles it would not be detectable unless the correlation between getting shingles and subsequent dementia were extremely high. And if that were the case, surely other studies (and this one) would have picked up a very obvious connection.
And there’s always the chance of something worse than that.
My mother wound up in the hospital, with the left side of her face paralyzed for weeks and partially so for longer, and her balance never fully recovered. That’s quite rare – but it’s a possibility. (The shingles infection went into the nerves for her face and inner ear.)
– each shingrix shot left me feeling mildly crappy for a day. Even severely crappy for several days would have been worth it.
I’ve had that too; it was available years before Shingrix was.
That’s a good point – if the association isn’t due to something involving the virus, but instead is something else about the vaccine, Zostavax might have the effect but Shingrix might not.
Oh better yet, especially from my point of view: while several of her siblings were diagnosed with Alzheimer’s, my mother’s diagnosis was vascular dementia. Whether all the diagnoses were correct I don’t know.
However reserving judgement on whether this is real. As the OP stated, right now it’s a twitter thread.
A mind more able to make good connections, and better able to balance short-term pain and long-term potential benefits?
That might well apply to other medical decisions, however. Did they check against any other such decisions?
Unless what’s specific is something about brain function, but not specific about the vaccination.
The question isn’t just whether people who got this vaccine were less likely to get dementia. The question is also whether people who made other similar medical decisions are also less likely to get dementia – in which case, what’s going on seems more likely to be that one of the earliest symptoms of dementia can be difficulties making good judgements. This can show up, in relatively subtle form, well before the person’s diagnosed with dementia.
I don’t think this is adequate to address the key point - that in this study there is such a highly specific protection against dementia, but no other disease (other than shingles, of course).
I didn’t ignore it. I meant that an inability to judge that the vaccine’s worth it might be part of a difficulty in making judgements that can be a very early symptom of dementia, before it’s diagnosed – in other words, that the association might be that people who got the vaccine were less likely to already be in very early stages of not-yet-recognized dementia.
If that’s what’s going on, then the test for it isn’t whether the vaccine protects against other diseases; it’s whether people who made sensible decisions about other things – including other medical procedures – are also less likely to be diagnosed with dementia later on.
editing this [ see below ]
But since the background incidence of dementia is around 15%, any such effect would have to be large - it is diluted around sevenfold. How strong do you really think the effect could be for people who as yet have no detectable symptoms of dementia to be so much less likely to get a shingles vaccine?
And again, note that there is an effect at p=0.02 even when just comparing eligible vs ineligible groups, without regard for who actually got vaccinated in the eligible group. (Of course the effect is smaller, since only around half of the eligible group were vaccinated.)