"Cognitive stimulation is one of the areas where we did find some benefit. The exact type of stimulation that an individual uses is not as important as being intellectually engaged," Burke said.

The expert review also found insufficient evidence to recommend any drugs or dietary supplements that could prevent or slow cognitive decline.

However, given that there is at least some evidence for positive effects from some of these lifestyle changes, plus other benefits apparently unrelated to cognitive decline, Burke offered some recommendations.

"I think that by having people adopt a healthy lifestyle, both from a medical standpoint as well as nutritional and cognitive stimulation standpoint, that we can reduce the incidence of cognitive decline, which will be proof that these factors are, in fact, important."

James Burke of Duke University is one of the authors of a study reviewing previous research on cognitive decline. The paper is published online by the Annals of Internal Medicine.