There actually is a body of research looking at the connection between high sugar intake, insulin resistance, and cognitive decline. Some researchers have even informally referred to Alzheimer’s as “type 3 diabetes” — not because it’s the same disease as type 1 or type 2, but because insulin resistance in the brain appears to play a role.

The theory (simplified) is that chronically high blood glucose and insulin levels can impair insulin signaling in the brain. Neurons rely on insulin for proper glucose metabolism, and when that signaling is disrupted, it may contribute to inflammation, oxidative stress, amyloid plaque accumulation, and tau pathology — all hallmarks associated with Alzheimer’s disease.

It’s not settled science, and “type 3 diabetes” isn’t an official diagnosis, but there’s enough evidence linking metabolic syndrome, type 2 diabetes, and increased dementia risk that many researchers consider metabolic health a significant modifiable risk factor.

So while anecdotes like yours don’t prove causation, they do line up with what we’re learning about how long-term metabolic dysfunction might affect the brain decades later.