I wonder how far away we are from the future where a blood sample is able to predict your propensity for a huge range of possible ailments (from Alzheimer’s to the flu). Feels very sci-fi, but also within reach.
some molecules/enzymes/structures are only made in response to a disease- so i'd say analyzing DNA/RNA capability would be more useful than analysis what's currently floating around in the blood.
For late-life diseases though, it's likely they are linked to exposure to something during the individuals lifetime (i.e. parkinson's disease from pesticide exposure) and genetic makeup can only predict probabilities for susceptibility.
Alzheimer's specifically is thought to be linked to chronic aluminum exposure (e.g. water treatment, antiperspirant deodorant, etc.).
"At present, there is no strong evidence to support the fears that coming in to contact with metals through using equipment or through food or water increases your risk of developing Alzheimer's disease."
https://www.alzheimers.org.uk/about-dementia/risk-factors-an...