Carl Heneghan

So it's completely opposite in effect.

And so one of the things when you look at that evidence, and not to say it's even more confusing, because if you look at that 2016 review,

Some of the studies included that were the same studies that are included in this 2020 study, which people will know observational study that was used for like hormone replacement therapy and HRT, where it came to a directly opposite conclusion to some of the trials.

But the idea being is, I think that what's happening here, we are confusing the public significantly by producing single studies that get picked up.

They have significant altmetric scores.

The news loves them.

But nobody then places them in the context of pre-existing evidence.

Yeah, well, one of the things I say first is to say it's very difficult when outcomes are rare for harms.

The quality of the evidence is always moderate because largely these studies were never set up to address that specific question.

So most of this is coming after the effect.

So there's recall bias, reporting bias, missing data, issues with the studies.

And what you find is people say statements like there's no definitive evidence that tau causes cancer.

Well, the definitive evidence will only ever come post postmortem when you can have pathological proof.

Therefore, one of the things I do is think of this in the context of the law.

And the law thinks about it on the basis of balance of probabilities.

And if you think about it in a balance of probability approach, you say, based on the best available evidence, is the occurrence of the event more likely than not?

And to do that, you need all of the evidence, not just a single bit of evidence.

And so you end up cherry picking.

If you're not careful and the media is loving it.

But my problem is at the end of the day is the public is utterly confused.