Yeah, so this actually was a study that was really inspired by a very simple question. We wanted to know what it meant to have a very high p-tau217 level in the blood of a cognitively unimpaired older adult. What would that tell us about somebody’s risk of cognitive impairment over, say, 2, 5, or 10 years. Seems like a simple question but actually there’s really little data so far to speak to it...
Yeah, so this actually was a study that was really inspired by a very simple question. We wanted to know what it meant to have a very high p-tau217 level in the blood of a cognitively unimpaired older adult. What would that tell us about somebody’s risk of cognitive impairment over, say, 2, 5, or 10 years. Seems like a simple question but actually there’s really little data so far to speak to it. So what we did is we took six different studies six different cohorts of participants up to about 2700 older adults and we looked at their levels of plasma p-tau217 in the blood which interestingly is a marker of amyloid load in the brain based on a PET scan, even though it has the word tau in it. And so we were really interested in looking at how that was associated with cognitive impairment across all of these individuals. In order to do that, we combined all the data together. And what we found was really striking, that over about five years, those with very high levels of p-tau217, had about 38% risk of cognitive impairment over five years, and up to 78% over 10 years. We were quite struck by that because within each of the cohorts, there was quite a consistent finding, not just at a pooled level. In addition, we also ensured that every single individual also had an amyloid PET scan. What we wanted to do was to see how well p-tau217 performed, even after adjusting for the amyloid PET scan, because we know that those two are closely related. And what we found was that p-tau217 was still very strongly associated and actually imparted more information than an amyloid PET scan. So we’re sort of scratching our heads as to why that might be. And we think it’s because, you know, p-tau217 is not just associated with amyloid PET. There are other things that it is associated with. We think that there might be something about the amyloid itself that’s bothering the tau or that is perturbing the tau, which is causing sort of synaptic problems and other sort of signals that are coming out in the blood, which p-tau217 is capturing. And so we’re really excited by that. There were a couple of caveats to the study that I think are important to point out, that we didn’t have a huge amount of longitudinal data after 10 years. So our estimates are sort of a first step in that direction. We need to gather more data longitudinally. And the other thing is that these cohorts, even though there were many of them and many thousands of individuals, a lot of these were from convenience cohorts, which means that they generally are highly educated. They tend to be lower in diversity, both racially and ethnically. So we really need to have, you know, more epidemiological studies, larger studies with people from all walks of life to really ascertain what the p-tau217 blood is telling us.
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