Can you delay dementia?

No: So far there is no definitive evidence showing how to delay the onset of dementia. Exercise has the most robust support but it is not definitive. There are dementia specific medications to delay functional decline though they do not change what is happening in the brain.

Yes: Some neuroscientists are promoting to learn new and complex things always to increment the number of glial cells and dendrites. Also some promote to keep learning until you die. Some physicians prescribe medicines for dementia even if not sure is only forgetfulness, mild cognitive impairment or early dementia. Medicines supposedly delay the progression of the disease.

Blood pressure: In addition to the previous answers given, there is some evidence that controlling your blood pressure, controlling your cholesterol, and staying active help delay onset of some forms of dementia.