It doesn't change the fact that there is no actual causal evidence. Perhaps the demented brains simply suck at flushing out microplastics as well. If you ever find people with more microplastics exposure have more dementia (like they did for asbestos and lung cancer), then you're onto something. But no rigorous study has found this yet. And if they do, you will hear of it immediately for sure, given how much reporting there is for microplastics=bad for you.