Previous reports had shown that late-life social engagement seemed to be protective against dementia. Many of those studies were based on data collected closer to the onset of dementia, however. These current researchers wanted to look at earlier time frames.

A low level of midlife social activity, on its own, was not associated with an increased risk of dementia, the researchers report. However, any decline in social activity from midlife into late-life did seem to raise dementia risks, the team found, as did poor social engagement in late life.

A second study found that older Japanese-Americans who drank fruit or vegetable juices at least three times a week lowered their risk of developing Alzheimer's by 75%, compared with people who drank these juices less than once a week.

A third study found that physical activity and moderate alcohol consumption might also help maintain cognitive ability later in life.

In general, researchers concluded, these findings fit nicely with the Alzheimer's Association's new "Maintain Your Brain" initiative, which stresses staying mentally active, socially active and watching diet and exercise.