I don't think this proves much. The group with the intervention did better on some standardized tests after the study was over. In general, as I understand it, people who do better on those generally have a lower risk of Alzheimer's disease.
But, that is very different from saying these interventions lowered the risk of Alzheimer's disease. It is entirely possible that people who go through such an intervention may do better on those tests but don't actually have a lower risk of Alzheimer's disease. And, it is possible that people even if they do better right now on those tests that the change will not persist.
I don't think you can measure whether some might get Alzheimer's 10 years later or 15 years later, etc. based upon tests taken right after the intervention.
There are other questions. How did they choose people? They said it was people who already had some cognitive decline? How much? What kind? Also they were coaching people on lifestyle changes. What about people who weren't obese or didn't have a poor diet? Did they show improvement or was there only improvement with those who have a lot of changes to make.
That is. Let's say there is a study that wants people to eat 1 ounce of nuts every day. And, I am randomly assigned to that group. They will not see any changes to my risks markers after X amount of time of eating 1 ounce of nuts a day because I already do that.
So, even if these interventions do improve cognitive function, etc. will it do so for those people for whom this is not a major lifestyle intervention?
I am not saying this study was worthless. Indeed, it is indicated to be a proof of concept study to guide further research. I think it is fine for that. But, likewise, not many conclusions can be drawn from it.
(That said, it does sound like most of those changes are good things to do in any event).
There's been a number of other published studies along the same lines, in mice and humans. Plus there's all the research coming out of Loma Linda, where many of the inhabitants follow a Seventh Day Adventists lifestyle and the seniors have very low rates of any kind of brain impairments compared to the surrounding communities.
There's not much downside to following the diet and lifestyle changes since it is starting to look the recommendations that protect the brain are also heart healthy, help prevent cancer and lead to longer life spans (in human and animal studies).
In the study above they measured risk factors for Alzheimer's before and after the study:
"Lifestyle risk factors for AD were assessed using the Australian National University‐Alzheimer's Disease Risk Index (ANU‐ADRI), and cognition was assessed using Alzheimer's Disease Assessment Scale‐Cognitive subscale, Pfeffer Functional Activities Questionnaire, Symbol Digit Modalities Test (SDMT), Trail Making Test‐B, and Category Fluency.
The primary analysis showed that the intervention group had a significantly lower ANU‐ADRI score (χ2 = 10.84;
df = 3;
P = .013) and a significantly higher cognition score (χ2 = 7.28;
df = 2;
P = .026) than the control group. A secondary analysis demonstrated that the changes in lifestyle were driven by increases in protective lifestyle factors (χ2 = 12.02;
df = 3;
P = .007), rather than a reduction in risk factors (χ2 = 2.93;
df = 3;
P = .403), and cognitive changes were only apparent for the SDMT (χ2 = 6.46;
df = 2;
P = .040). Results were robust to intention‐to‐treat analysis controlling for missing data."
https://onlinelibrary.wiley.com/doi/abs/10.1111/jgs.16762?af=R
