Norbert: As I age I think about my mom's advice to me many years ago: "Don't get old."

Dave: Hmm... how's that workin' out for ya'?

Norbert: Some days are better than others, that's for sure. What she meant was do all the right things to stay healthy and delay dementia.

In forty years, global dementia cases are expected to triple, and despite all the medical advances, there's still no magic pill to prevent it.

The upside is that epidemiological studies show we each can delay our own mental decline.

Enough studies have linked dementia with low physical and mental activity, obesity, hypertension, and hyperlipidemia. One recent study reinforced the strong correlation between exercise and a robust mind. Walking, running, and weight lifting are all effective.

A lot of older Americans now use computer games to pump up their minds. A study did show that playing improved their language and reasoning skills for at least a year. Other studies, though, indicate that the positive effects decline with age.

Many people believe in nutritional supplements. While there's no conclusive evidence they work, in a few cases they do. For example, in people with nutritional deficiencies vitamins do improve cognitive abilities, especially B-12 and folic acid.

But people who have normal levels of these vitamins and take more in the form of supplements don't experience a delay of cognitive impairment. In fact, mega doses of supplements can be toxic.

One study found that supplementing with omega-3 fatty acids such as fish oil has a small effect on verbal abilities but no effect on motor skills or memory.

So, for now, your best bet is what you hear most often: get physical and mental exercise, and maintain a healthy diet and weight.