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

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 consider is potential confounders. There is a big list of covariates they included into their model here: https://content.iospress.com/articles/journal-of-alzheimers-...

There are quite a few things that can be done to alleviate potential false correlations: DAGs, prior literature, removing confounders, and including covariates are all things at disposal.

3. Such a large sample size + previously reported findings + an inclusion of enough covariates still doesn't == causation, BUT it's important to publish and shout about so we can then look into the potential biological underpinnings that may cause this. Which by the way, those experiments may still use data science techniques.

4. If you are actually interested, there is a whole topic of this called 'causal inference' with one famous criteria list called the 'Bradford Hill Criteria': https://en.wikipedia.org/wiki/Bradford_Hill_criteria. This list is often argued about.

5. If all of this information was new to you, please stop spouting 'correlation != causation'. You probably don't know as much as you think

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 an interview for the article. That's the reason (1) the general public misunderstands (2) people scream about it. Scientists get points for "high-impact research," and there is strong incentive to be dishonest.

(As a footnote, personally, I do believe it is causation; I believe that as with COVID and EB, we've dramatically underestimated the long-term impact of many viral infections. But that's just a personal belief.)

>The scientists said it was causation.

Interesting. I don't read that as claiming causation, I read that as describing the correlation.

You're right though, it's confusing messaging, regardless.