People who are free of dementia and have high levels of a protein that indicates the presence of inflammation have relatives who are more likely to avoid the disease as well, according to a new study published in the August 15, 2012, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"In very elderly people with good cognition, higher levels of C-reactive protein, which is related to inflammation, are associated with better memory," said study author Jeremy M. Silverman, PhD, with Mount Sinai School of Medicine in New York. "Our results found that the higher the level of this protein in the study participant, the lower the risk for dementia in their parents and siblings."

For the study, researchers identified 277 male veterans age 75 and older and free of dementia symptoms. They were given a test that measured levels of the protein. Next, the group was interviewed about 1,329 parents and siblings and whether they had dementia. A total of 40 relatives from 37 families had dementia. A secondary, independent group of 51 men age 85 and older with no dementia symptoms were given an interview about 202 relatives for dementia. Nine of the relatives had dementia.

Study investigators found that participants who had higher amounts of the protein were more than 30 percent less likely to have relatives with dementia. Similar results were found in the secondary group. Since the protein levels were not associated with years of education, marital status, occupation and physical activity, these factors could not account for the lower risks seen.

"This protein is related to worse cognition in younger elderly people. Thus, for very old people who remain cognitively healthy, those with a high protein level may be more resistant to dementia," said Silverman. "Our study shows that this protection may be passed on to immediate relatives."

The study was supported by the National Institute on Aging, United States Department of Veterans Affairs, the Berkman Charitable Trust and the Alzheimer's Association.