An important component of achieving extreme old age is the delayed onset of dementia, Cosentino said. About 5.4 million Americans are estimated to have Alzheimer's disease, most of them older than 65 years.
Another expert said other studies have shown similar protection against heart disease and cancer in long-lived families.
"This finding suggests that factors that protect the cardiovascular system and perhaps factors that ward off cancer could be at work in the brain to prevent Alzheimer's," said Dr. Sam Gandy, associate director of the Mount Sinai Alzheimer's Disease Research Center in New York City.
This new study dovetails perfectly with papers showing the essential role of inflammation in Alzheimer's dementia, Gandy said. "And some of the factors that cause Alzheimer's . . . share enormous similarity with blood vessel inflammatory diseases that probably contribute to cardiovascular disease and cancer," he said.
Overall, the study found that 38.5 percent of participants developed Alzheimer's disease. The risk was slightly reduced in men and women from long-lived families compared with their husbands or wives.
Moreover, the risk was further reduced among their sons and daughters, but did not carry over to nieces and nephews, the researchers found.
For more information on Alzheimer's disease, visit the Alzheimer's Association.
SOURCES: Stephanie Cosentino, Ph.D., assistant professor, neuropsychology, Columbia University Medical Center, New York City; Sam Gandy, M.D., associate director, Mount Sinai Alzheimer's Disease Research Center, New York City; May 6, 2013, JAMA: Neurology, online
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