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Researchers have identified a number of factors that seem to stave off cognitive decline, from reading to making art and practicing yoga. A new study points to yet another: having close friends.

Data from an ongoing study of people in their 80s and above with superior memories finds they differ from their cognitively average peers in one key way: They enjoy more warm, satisfying social relationships.

This intriguingly suggests positive social interactions may slow the age-related decline in certain regions of the brain that are key to retaining mental sharpness.

"It's not as simple as saying if you have a strong social network, you'll never get Alzheimer's disease," study author Emily Rogalski of Northwestern University said in announcing the findings. "But if there is a list of healthy choices one can make, such as eating a certain diet and not smoking, maintaining strong social networks may be an important one on that list."

The study examined data from Northwestern's SuperAging Program, which features "individuals over age 80 with episodic memory ability at least as good as middle-age adults." Episodic memory is the ability to bring to mind and recount one's unique memory of a specific event.

Participants were 31 "SuperAgers" and 19 peers who were cognitively average for their age. The two groups had very similar demographic characteristics, including levels of intelligence.

All completed a questionnaire in which they rated their psychological well-being. They expressed their level of agreement with a series of statements, covering such topics as personal autonomy, self-acceptance, life purpose, and positive relations with others. The latter category included assertions such as "I know that I can trust my friends, and they can trust me."

The SuperAgers scored higher in only one category: satisfying relationships with others. "It appears that social relationships in and of themselves are important to the maintenance of cognition," the researchers write.

In the online journal PLoS One, lead researcher Amanda Cook Maher and her team note that previous research has found the SuperAgers' brains are measurably different than those of their peers. This raises the intriguing possibility that positive, close interactions may have brain benefits, which decelerate the rate of cognitive decline.

The president of the AARP Foundation recently estimated that as many as 40 percent of American seniors suffer from loneliness. These results suggest that's not only sad—it may be dangerous to their mental and emotional health.

Is it time to take your favorite senior citizen out for lunch and a stimulating chat?