Published in the most recent Lancet: “A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial”
This was a strong randomized prospective control study that involved diet, exercise, and cognitive training. You can read the abstract here.
The paper itself is behind a pay wall, so I can not give you details about the intervention. Some more information can be found in the press release.