How to maintain mental abilities until deep old age?

 "Resilience, on the other hand, characterizes people with normal cognitive abilities even though their brains may have damage typical of Alzheimer’s, the leading cause of dementia. In addition to plaques and tangles, such changes include loss of neurons, inflammation and clogged blood vessels.
People with cognitive resilience are able to accumulate “higher levels of brain damage before clinical symptoms appear,” the Dutch team reported.

Many studies have revealed that a variety of lifestyle factors may contribute to resilience, Dr. Stern said. Among them are obtaining a higher level and better quality education; choosing occupations that deal with complex facts and data; consuming a Mediterranean-style diet; engaging in leisure activities; socializing with other people; and exercising regularly.
“Controlled trials of exercise have shown that it improves cognition,” he said. “It’s not just a result of better blood flow to the brain. Exercise thickens the cerebral cortex and the volume of the brain, including the frontal lobes that are associated with cognition.”
Dr. Perls said, “Alzheimer’s disease is not an inevitable result of aging. Those genetically predisposed can markedly delay it or show no evidence of it before they die by doing the things we know are healthful: exercising regularly, maintaining a healthy weight, not smoking, minimizing red meat in the diet, and doing things that are cognitively new and challenging to the brain, like learning a new language or a musical instrument.”
Also important is to maintain good hearing, said Dr. Perls, a 60-year-old who wears a hearing aid. “I can’t emphasize enough how important it is for people to optimize their ability to hear,” he said. “There’s a direct connection between hearing and preserving cognitive function. Being stubborn about wearing hearing aids is just silly. Hearing loss results in cognitive loss because you miss so much. You lose touch with your environment.”
Vision, too, is important, especially for people who already are cognitively challenged. “Poor vision makes cognitive impairment worse,” Dr. Perls said. As his brain-challenging activity, he’s taken up birding, which requires both good hearing and good vision."