A study at Cardiff University in the United Kingdom shows that exercise beats dementia reports the U.K. Independent. 
Well, exercise along with following three of the other five key behaviors.
But exercise is by far the most important one according the study.
The five “key behaviors” are not smoking, having a low bodyweight, a healthy diet and low alcohol intake.
Following four of them appears to reduce dementia risk by 60 percent while cutting the chance of heart disease and stroke by 70 percent.