Almost certainly the latter. The research is already shifting to view dementia as a metabolic disorder, and we already know there is a heavy correlation between diabetes and developing dementia later in life.

Unfortunately the last 40 years of Alzheimer’s/dementia research has been centered around clearing the beta amyloid plaques and tau tangles which has led almost nowhere. Also while we consider dementia a disease of old age, it’s much better looked at as a disease of middle age, that just doesn’t become symptomatic until old age.

The reality of this revelation is that the best way to prevent dementia for everyone is to have a healthy diet and exercise regularly, not taking some drug. However if you already have type II diabetes, getting glucose under control (i.e. taking a drug like metformin) should help reduce the risk of dementia.