What Actually Goes Wrong
The brain doesn't fail in one way
Dementia isn't one disease — it's a final common pathway for at least five distinct pathological processes, often running in parallel. Understanding which ones apply to YOU is the difference between generic "do puzzles" advice and targeted prevention that actually changes your trajectory.
The five major mechanisms
Amyloid plaques + tau tangles (Alzheimer's), vascular damage (strokes, micro-infarcts, white matter lesions), Lewy bodies (Parkinson's + DLB), TDP-43 (LATE — limbic-predominant age-related TDP-43 encephalopathy, very common but poorly recognised), and inflammation-driven neurodegeneration. Most dementia cases involve TWO OR MORE of these running at once.
Silent for decades
Amyloid starts accumulating 20–30 years before symptoms. Vascular damage can begin in the 30s in people with hypertension or metabolic disease. By the time memory loss is noticeable, the pathological processes have been running for years. This is why primary prevention is so much more effective than treatment.
Match mechanism to driver
Connect each brain-aging mechanism to its primary modifiable driver.
This step is interactive — open the Thier app to try it.
Brain shrinks more than people realise
Adult brain volume peaks in the early 20s, then loses ~0.2-0.5% per year — accelerating after 60. By 80, the average brain has shrunk 5-10% in volume from its peak. The shrinkage isn't uniform: hippocampus and prefrontal cortex (memory + planning) lose volume fastest. Fortunately the rate is highly modifiable: aerobic exercise, sleep, and ApoB control all measurably slow it.
Key Takeaway
Dementia is a portfolio of diseases, not a single condition. Most people who develop it have multiple mechanisms running simultaneously. The silver lining: each mechanism has different modifiable drivers, and addressing any of them delays or softens the final decline.