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Time and time again we see epidemiological studies posting findings that are clearly best explained by correlation than causation. For example, think of the peo

Time and time again we see epidemiological studies posting findings that are clearly best explained by correlation than causation. For example, think of the people you've met with the worst teeth. They will almost certainly, on average, have worse overall health, lower socioeconomic status, lower intelligence, lower paid jobs, lower educational attainment, worse diet and so on. Surely these are just as likely, if not more, to be on the causal pathway for Alzheimers? And that's completely ignoring the fact that people with early Alzheimers which has not been diagnosed are much less likely to remember to keep up with oral hygiene rules, so the risk for reverse causation is HUGE. Now I know you're going to argue that the epidemiological studies account for this using multiple regression and so on, but the fact is time and time again it has been demonstrated that this just cannot be done. Indeed, vitamin D in practically every epidemiological study to date has shown to reduce the risk of cancer, cardiovascular mortality, tuberculosis infect. And yet, just this month, someone FINALLY did a randomised trial of vitamin D in TWENTY SIX THOUSAND people (the VITAL trial) and found it made no difference at all (in fact, cardiovascular death was slightly but non-significantly more common in the vitamin D group). Unfortunately, people's careers and publications rely on this stuff, so it'll keep coming. Please remain skeptical, hacker news.

ak39 8y ago
Vit D referenced study: https://www.nejm.org/doi/full/10.1056/NEJMoa1809944 https://www.nejm.org/doi/full/10.1056/NEJMoa1809944
nabla9 8y ago
This particular article refers to study that claims "evidence for causation" from experiments with mice and initial tests with human volunteers. They were given common antibiotic and it improved cognition. This is of course just exploratory testing with humans, to see if bigger experiments are justified but it's promising. Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors http://advances.sciencemag.org/content/5/1/eaau3333 http://advances.sciencemag.org/content/5/1/eaau3333 > Please remain skeptical, hacker news. But please, hacker news, don't poison comments with generic "causation is not correlation" tourette. Read the article first and make specific comments.
- BerislavLopac 8y ago
  > > Please remain skeptical, hacker news. > > But please, hacker news, don't poison comments with generic "causation is not correlation" tourette. Read the article first and make specific comments. Or in a nutshell: Hacker News, please apply scientific principles.
titzer 8y ago
I agree with some of your comment but I wanted to reply to one part I take issue with. > Please remain skeptical, hacker news. Sure, but please don't be the binary-kind of skeptic, the kind that believes that things are either causative or not causative and that everything in between is just "correlated" and that we somehow need to find out what the real causative thing is, and until then, we will not accept anything, until we have the smoking gun. That somehow we have must keep living in denial and ignore growing mountains of evidence because it's "murky" until it finally clicks over into "proven" and we change our minds. I don't think this article is as bullish on the idea as you might imagine. If anything, such articles should stretch our imagination as to what could be causing and contributing to Alzheimer's and other brain diseases. Like heart disease, it is likely that Alzheimer's as we understand it has a number of symptoms and causative factors that might be affected by thousands of variables. Just discounting whole lines of research this way is binary thinking. Kudos on those who did the Vitamin D study. But if we're constantly seeking a shocking repudiation or proof of every possible idea, the kind of slam-dunk that goes up in lights and earns everyone backslaps and Nobel prizes, we're already on the wrong mental track, IMHO. And all of this is not to give license to true believers who catch on an idea based on the thinnest of evidence. IMO skepticism and conspiracy-theory-mindedness are on opposite ends of the same spectrum, and both are close-minded in fairly damaging ways.
notacoward 8y ago
> the causal pathway The article very clearly distinguishes between the cause and a cause. "Alzheimer’s is a complex disorder, not a one stop shop" and so on. > best explained by correlation than causation They did more than that. They also found gingipains in the brains of patients. Those had to come specifically from P.gingivalis infection, not the other factors you mention. They identified a plausible causal pathway involving tau and amyloid beta, and they induced their production by introducing P.gingivalis in mice. That's a lot more than merely equating correlation with causation. Skepticism is good. Ignoring what has been presented is not skepticism, and neither is jumping from correlation to non-causation. That's just contrarianism.
- josephby 8y ago
  Mice don’t get Alzheimer’s. Inducing plaques is not the same thing as giving mice Alzheimer’s.
  - notacoward 8y ago
    No, it's not, but it proves that the link between gingipains and plaque is reproducible. That's part of the causative chain, so it still refutes the glib contrarianism to which I was replying.

ak39 8y ago

Vit D referenced study: https://www.nejm.org/doi/full/10.1056/NEJMoa1809944 https://www.nejm.org/doi/full/10.1056/NEJMoa1809944

nabla9 8y ago

This particular article refers to study that claims "evidence for causation" from experiments with mice and initial tests with human volunteers. They were given common antibiotic and it improved cognition. This is of course just exploratory testing with humans, to see if bigger experiments are justified but it's promising. Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors http://advances.sciencemag.org/content/5/1/eaau3333 http://advances.sciencemag.org/content/5/1/eaau3333 > Please remain skeptical, hacker news. But please, hacker news, don't poison comments with generic "causation is not correlation" tourette. Read the article first and make specific comments.

BerislavLopac 8y ago
> > Please remain skeptical, hacker news. > > But please, hacker news, don't poison comments with generic "causation is not correlation" tourette. Read the article first and make specific comments. Or in a nutshell: Hacker News, please apply scientific principles.

titzer 8y ago

I agree with some of your comment but I wanted to reply to one part I take issue with. > Please remain skeptical, hacker news. Sure, but please don't be the binary-kind of skeptic, the kind that believes that things are either causative or not causative and that everything in between is just "correlated" and that we somehow need to find out what the real causative thing is, and until then, we will not accept anything, until we have the smoking gun. That somehow we have must keep living in denial and ignore growing mountains of evidence because it's "murky" until it finally clicks over into "proven" and we change our minds. I don't think this article is as bullish on the idea as you might imagine. If anything, such articles should stretch our imagination as to what could be causing and contributing to Alzheimer's and other brain diseases. Like heart disease, it is likely that Alzheimer's as we understand it has a number of symptoms and causative factors that might be affected by thousands of variables. Just discounting whole lines of research this way is binary thinking. Kudos on those who did the Vitamin D study. But if we're constantly seeking a shocking repudiation or proof of every possible idea, the kind of slam-dunk that goes up in lights and earns everyone backslaps and Nobel prizes, we're already on the wrong mental track, IMHO. And all of this is not to give license to true believers who catch on an idea based on the thinnest of evidence. IMO skepticism and conspiracy-theory-mindedness are on opposite ends of the same spectrum, and both are close-minded in fairly damaging ways.

notacoward 8y ago

> the causal pathway The article very clearly distinguishes between the cause and a cause. "Alzheimer’s is a complex disorder, not a one stop shop" and so on. > best explained by correlation than causation They did more than that. They also found gingipains in the brains of patients. Those had to come specifically from P.gingivalis infection, not the other factors you mention. They identified a plausible causal pathway involving tau and amyloid beta, and they induced their production by introducing P.gingivalis in mice. That's a lot more than merely equating correlation with causation. Skepticism is good. Ignoring what has been presented is not skepticism, and neither is jumping from correlation to non-causation. That's just contrarianism.

josephby 8y ago
Mice don’t get Alzheimer’s. Inducing plaques is not the same thing as giving mice Alzheimer’s.
- notacoward 8y ago
  No, it's not, but it proves that the link between gingipains and plaque is reproducible. That's part of the causative chain, so it still refutes the glib contrarianism to which I was replying.