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WalterBright

First NIH said it does:

https://www.nih.gov/news-events/nih-research-matters/viagra-...

Then it doesn't:

https://www.nih.gov/news-events/news-releases/nih-dream-stud...

Then it does:

https://www.ox.ac.uk/news/2024-06-07-sildenafil-viagra-impro...

Who knows what to believe.

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> Who knows what to believe.

This may be a sincere statement, but I'm not sure it's a helpful one. What data do we have? A 2:1 advantage in published studies that it does help. Since there is no such thing in science as absolute proof of anything, these are pretty good odds. Certainly more work will be done in the future to try to replicate the results and figure out the one negative outcome. But until then, we cannot say that the evidence is in any way "equal" on both sides.

The first one is just a combination of some computer modeling guessing at possibly useful existing drugs and a look at the existing patient data showing that people who were on these seemed to have Alzheimer's less. It's very clear that it's just an initial step that doesn't actually show there's a benefit.

The second is more of that same basic kind of research, but weighing in the opposite direction: it showed no association with Alzheimer's for people with a specific other condition who got these drugs vs. ones with the same condition that didn't (also they did some cell culture testing outside the body that didn't show any effect/improvement).

This new one is an actual double-blind study giving people the drug. Equally important, it's not claiming an effect on Alzheimer's, but vascular dementia, a different form of dementia that's directly related to blood flow and therefore to Viagra's known effects. Of course it's still just really a marker for future research on if this is broadly useful.

Might be a 2:1 but we also have to take into account the level of evidence each study provides.

Studies aren't conducted at random, it's not really valid to sample them as though they were. Major selection bias.

Maybe these studies are particularly hard

They certainly are hard, because dementia is something that develops over years if not decades. Anytime it takes that long to do a single iteration of your experiment, it's hard!

Does it need to be, though? You can survey healthy but senior populations about their habits, and then over the following years track what happens.

If medical records were public, the answers could even be in those for any medicines that are prescription based. You could then make statements like "A% of patients who took drug B within C years did/didn't develop disease D".

That's not a randomized controlled trial though. You might find a correlation, but you couldn't actually establish causation, or eliminate hidden variables.

We have to get over this false meme where people think RCTs prove causation and the rest prove correlation.

An RCT doesn’t prove causation, it only might observe another correlation that contributes to our causal inferences based on the convergence of evidence.

We don’t have RCTs for most things that you take for granted.

Well, an observational-only study proves even less.

And any time the object of your study is also a treatment for ED it gets extra hard. ;-)

Don't worry, I caught your innuendo.

It’s hard science. I take viagra every day and have only become moderately demented, so obviously it’s working.

That seems a reasonable assumption.

This is like the supposed health benefits of drinking red wine. I don’t know if it’s true or not but it’s fun to find out.

I’ve always been taught that “a wank a day keeps the doctor away” so I believe it.

I guess it depends on the Doctor. /s

> Who knows what to believe.

Honest question: do we need to believe one or the other ?

Or can we get away with "it depends" or "it works on some subjects and not on others"

That second study didn’t use as robust of methods as the first, and they each used observational data that benefit from advanced methods (propensity score analysis).

With an RCT, the evidence is substantially increased.

I’d conclude sildenafil reduces risk of age-associated cognitive decline

Maybe they forgot what they said before?

Could be different for different folks

Different strokes for different folks?

All I know for certain is there's no dementia in my pants.

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