karelena wrote:This is a long article with a few surprises. It is interesting that so many studies had contradictory results. ...
I agree that it's frustrating to have consensus only around what seem like obvious recommendations: Exercise is important, a Mediterranean-style diet is better than the "Standard American Diet"; avoiding serious or repetitive head injuries is a good idea, avoiding diabetes is preferable, etc. Even some of the conclusions of previous studies are now being re-interpreted. For example, the abstract notes that a higher educational level is associated with a faster cognitive decline. Note that it doesn't say "earlier"; it says "faster". Scientists have now charted that decline over time with longitudinal studies and it appears that what is happening is that people with higher education levels or "higher cognitive reserve", can compensate or show "resilience" to observable signs of reduced connectivity in the brains, or vascular damage, or hippocampus atrophy, by using their cognitive strengths--until they can't, and then they show a more rapid decline. So that's one example of how something that is "associated" with cognitive decline is not really a sign of a risk factor, but more a sign of the brain's actions to fight off decline.
From sitting in on meetings of scientists who work on basic research in Alzheimer's, it is clear that the understanding of the mechanisms of pathology are complex, and vary across people probably due to their history (TBI, diabetes, vascular issues), their individual genome (not just ApoE 4, but other risk and protective genes); their microbiome, their brain's inherent structure and resiliency and yes, their use of various supplements, like B-12, among others.
It's also clear that Alzheimer's may be a much more complex disease than was first thought, and it may be that a significant minority (maybe a third) of the cases identified as "Alzheimer's" in past studies were actually mixed dementias, or vascular or Lewy Body dementias, or something else.
But the research is still making great strides, and the imaging and use of machine learning, using massive data sets to have computers find subtle patterns in genome-wide-association-studies (GWAS) and in records of individuals are both expanding the rate and degree of learning. Scientists are also using sophistivated statistical models to study both plant-based and genetically-engineered possible interventions, and identifying "targets" throughout the brain's processes that might allow prevention to occur.
It's very hard to study dozens of supplements at once; so for now, I think people make their best calculation about what their risks and targets for their own personalized approach will be. I hope that is working for you.