Recent research has identified many conditions and interventions that, when properly treated or controlled, associate with a lower risk of mild cognitive impairment, dementia, or Alzheimer’s disease (AD). These studies have not attempted to prove a causal link between the risk factor evaluated and AD or a related disorder (ADRD). However, they do prove that something - either the risk factor or something strongly associated with it - reduces ADRD risk. Whether it is the risk factor studied or something tightly linked to that risk factor is what is not known.
This lack of knowledge of the causal link to ADRD should not discourage people from reducing their risks for hypertension, heart disease, stroke, high cholesterol, obesity, diabetes, cancer, vitamin B12, folate, and D deficiencies, and other risk factors associated with ADRD. If they turn out not to be causally linked to ADRD, then something strongly associated with them will be causally linked, and it is quite likely that reducing the risk factor may simultaneously reduce the causal link that is strongly associated with the risk factor.
Given this understanding of the difference between association and cause, it is reasonably possible to delay onset and progression of ADRD by 35-50%, which translates into a 3-5 year delay. Given that the average age of onset is 74 years old, a 4-year delay in symptoms would match the average American's life expectancy of about 78 years, which would eliminate the appearance of symptoms or allow one to live out their life with only mild ADRD symptoms.
If you notice changes in memory or other cognitive functions in yourself or in others, professional evaluation and treatment should be sought immediately.