The studied 1100 elderly people across northeastern Illinois, who did not have dementia to participate in the Rush Memory and Aging Project. Brain autopsy was done at the time of death and post mortem data was available for analysis from the first 89 people. Many elderly people who had the tangles and plaques which are associated with Alzheimer's disease did not clinically experience cognitive impairment or dementia. Hence Bennett concluded that social networks offer a protective shield against clinical manifestations of Alzheimer's disease.
Participants also underwent clinical evaluations and 21 cognitive performance tests each year. To understand the social network participants were questioned about the number of children they have, how many do they meet in a month, the number of relatives, excluding spouse and children, and friends to whom they feel close and with whom they felt at ease and could talk to about private matters and could call upon for help. It was found that as the size of the social network increased, the same amount of pathology had less effect on cognitive test scores.
The effect was evident across different kinds of cognitive abilities, but was most evident for semantic memory, which is important for knowledge about the world and is fundamentally involved in unique human cognitive processes such as language. Identifying factors associated with the ability to tolerate the pathology of Alzheimer's disease has important implications for disease prevention. Apart from education healthy and frequent interactions with friends and family have a positive impact as well.