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Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

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Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#81

Post by 2muchcoffeeman »

toolz wrote: post #74
sudosysgen wrote: post #70

Earlier quoted context omitted.

Correlations do imply a link, though. They don't imply causation, but in the absence of selection bias and with enough of a sample size, it is almost certain there is a link somewhere.

Well let's test this theory out then. Would you say I was being ridiculous if I told you that the number of people who drown in a year is linked to how many movies nicolas cage appears in? If so, then you might not actually believe linked is simply a synonym for correlation. I know I certainly would think that was a ridiculous way to phrase it.

That's just being facetious though. We've all seen that website with funny correlations. This line of argument while an important lesson to look deeper into systems before claiming a correlation doesn't really add much here.

Loads of people get the flu vaccine. Enough that I'd imagine the sample size is representative of the population at large. A large number of people also don't get the flu vaccine. So this is a surprising result. Especially since we are injecting a liquid into the people so there could reasonably be some effect we never thought of. Which is the whole point. These people aren't correlating things in completely unrelated fields and claiming a link.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#82

Post by Fomite »

dangom wrote: post #4

That's an incredible effect size. Mechanisms hypothesized to be at play: "These mechanisms—and those underlying the effects of adulthood vaccinations on all-cause dementia risk in general—can be grouped into at least three broad, non-exclusive categories: 1) influenza-specific mechanisms, including mitigation of damage secondary to influenza infection and/or epitopic similarity between influenza proteins and AD patho…

Whether or not that's an incredible effect size sort of depends. For infectious disease epidemiology, which regularly sees extremely strong effects because of the very short causal chain between an infection and an outcome, it's not all that extraordinary.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#83

Post by mortenjorck »

itsoktocry wrote: post #32
i_love_limes wrote: post #26

Epidemiologist in training here... There are quite a few comments in this thread already jumping on the 'correlation != causation' train. While that is true, I'd like to clarify a couple things: 1. The journal article didn't suggest it was causal. But such a correlation with such a large population warrants publication and further research into causation. 2. literally the first thing that any epidemiologist would con…

> There are quite a few comments in this thread already jumping on the 'correlation != causation' train. Complaining about correlation not being causation is the perfect theme for the midwit meme. It's one of my pet peeves.

The brainlet and sage text is “maybe x causes y.”

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#84

Post by gweinberg »

Symmetry wrote: post #73
thaumasiotes wrote: post #68

Earlier quoted context omitted.

Causation frequently removes correlations that would otherwise exist.

I don't think that's right? In theory you could have A and B that were naturally correlated and add a causal relationship between the two that exactly canceled that correlation but that would be infinity unlikely to happen by chance. In practice the only way that A and B can be correlated is that either A causes B, B causes A, or some C causes both A and B. Interestingly if both A and B cause C the C and A as well as…

It's not by chance. If you have a heater controlled by a thermostat, it destroys the correlation that would otherwise exist between outside temperature and inside temperature. That particular example sounds silly because it is so obvious. But in economics you can find examples where you would be seeing a relationship, but it is masked by an active response to the cause, but it's not so obvious this is happening.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#85

Post by headsoup »

kixiQu wrote: post #77
amacneil wrote: post #44

Earlier quoted context omitted.

If they only intend to claim correlation, avoiding the word "linked" in the announcement would probably help with general public interpretation. I feel like in English, "linked" usually implies some sort of potential causation, not just a general relationship. For example: "boyfriend linked to murder case".

What's wrong with implying potential causation? Correlation is potential causation. The whole reason one says the boyfriend is linked to the murder case is because one isn't saying he's responsible -- and yet he might be.

Probably just because it isn't a very high bar. "People who eat McDonald's linked to fewer car accidents." I mean some data might just show that, but causality is a lot further away there.

Hence, while a correlation might be interesting, when presented we need to also understand the methodology and go into the detail a little bit to see how extra factors have narrowed down that finding.

E.g, without looking into any of the data, 'more Flu shots reduces risk of Alzheimer's' might be because people predisposed to Alzheimer's have a poor diet and the flu shot just counters some other terrible health effect. So first bit of detail to look at is whether the selection factors for diet, comorbidities, environment, general health, history, etc.

Not saying anything about this article, but context is always important, hence those claiming 'correlation !== causation' are only correct as far as not looking any deeper. Same for 'well it could be' is useless without knowing how close to 'could be' it is.

More critical imo, is the use of '40% reduction.' If this is relative risk (this study is not, it's absolute), the actual risk could be 0.0037%, where a reduction of 40% is practically nothing. So next check is: is this relative or absolute risk? If relative, relative to what baseline? So many studies are distorted by using relative risks against a meaningless baseline.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#86

Post by sudosysgen »

toolz wrote: post #74
sudosysgen wrote: post #70

Earlier quoted context omitted.

Correlations do imply a link, though. They don't imply causation, but in the absence of selection bias and with enough of a sample size, it is almost certain there is a link somewhere.

Well let's test this theory out then. Would you say I was being ridiculous if I told you that the number of people who drown in a year is linked to how many movies nicolas cage appears in? If so, then you might not actually believe linked is simply a synonym for correlation. I know I certainly would think that was a ridiculous way to phrase it.

Congratulations, you've discovered p-hacking.

I said "almost certain". What you did is taken a database of someone who made millions of comparisons, such that coincidences that are very unlikely to occur happen via pure coincidence.

Additionally, I said "enough of a sample size". Given that the analysis you're talking about was over 11 pairs of points, that doesn't even qualify as very unlikely.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#89

Post by dang »

bilsbie wrote: post #33

I posted this exact link two days ago. What gives?

There's a lot of randomness in what gets attention on /newest. Your submission didn't get attention while this one did.

HN disallows reposts within 8 hours or if a story has had significant attention in the last year, but neither of those were the case with this repost, so our software allowed it to go through.

I know it's frustrating when your submission 'loses' and someone else's 'wins', but since it's random, it at least evens out in the long run if you submit lots of good stories. Eventually we'll implement some sort of karma sharing to take care of this.

Re: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease

#90

Post by bawolff »

spandrew wrote: post #69
blagie wrote: post #36

Earlier quoted context omitted.

The scientists said it was causation. "We found that flu vaccination in older adults reduces the risk of developing Alzheimer’s disease for several years. The strength of this protective effect increased with the number of years that a person received an annual flu vaccine – in other words, the rate of developing Alzheimer’s was lowest among those who consistently received the flu vaccine every year" Yes, that's in a…

This is a mischaracterization of even the words you've quoted. The team did indeed find that flu vaccines reduced the risk of Alzheimers. But he specifically doesn't say they know why the flu vaccine lowers the risk . Ie. They can't claim causation if they don't understand the underlying reason for the change. That's not how science works. In fact in the article in question he says the opposite: That the immune syste…

I disagree that's a mischaracterization.

> The team did indeed find that flu vaccines reduced the risk of Alzheimers. But he specifically doesn't say they know why the flu vaccine lowers the risk

I don't think that's an accurate statement. They didn't find it reduced risk. They found that there seemed to be a pattern. That's different then saying the flu vaccine reduced risk. Its possible that the vaccine is just a coincidence.

But the pattern looks pretty strong so its interesting news nonetheless.

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