The findings were the same even after researchers adjusted for education level, age when symptoms began, living situation, and other factors that could affect how long the study participants lived. Autopsies showed that the severity of the disease was similar among the ethnicities.

The study involved nearly 31,000 people with Alzheimer's who were seen at Alzheimer's Disease Centers across the country. Of the participants, 81 percent were white, 12 percent were African American, four percent were Latino, 1.5 percent were Asian and .5 percent were American Indian. They were followed for an average of 2.4 years. The participants lived for an average of 4.8 years after being diagnosed with the disease. Autopsies were performed on 3,000 of the participants.

Latino participants lived an average of about 40 percent longer than the white participants; African American participants lived an average of 15 percent longer than whites did. Asian and American Indian participants lived about as long with the disease as the white participants did.

"It's not clear why Latinos and African Americans have an advantage when it comes to living longer with Alzheimer's disease," said study author Kala Mehta, DSc, of the University of California, San Francisco, and member of the American Academy of Neurology. "Possible explanations may be underlying genetic or cultural factors."

Mehta said other factors that could account for the differences in surviving with the disease could be varying levels of social support from extended family, varying levels of health and diseases in addition to Alzheimer's disease, varying levels of treatment of other diseases, and differences in measurement or earlier diagnosis in some groups. Another factor could be length of stay in the United States; many participants came from other countries where the survival time with Alzheimer's may differ from in the United States.

"Determining the underlying factors behind this difference could lead to longer survival for everyone with Alzheimer's disease," Mehta said. "Regardless of the reason for this difference, these findings may have implications for health care planning for people with Alzheimer's disease."

Mehta says no general conclusions should be drawn about the inherent health or fitness of the ethnic groups involved.

The study was supported by grants from the National Institute on Aging and the National Alzheimer's Coordinating Center.

Note: If no author is given, the source is cited instead.

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