Nov. 14, 2007 -- Race may be an independent predictor of survival among people diagnosed with Alzheimer's disease, with Latinos and blacks living longer than whites.
The findings from a study involving nearly 31,000 patients treated at more than 30 Alzheimer's centers across the country revealed that, compared with whites, Latinos were 40% and African-Americans were 15% less likely to die during the study period.
The ethnic differences were seen even after researchers accounted for other factors known to influence survival, including education level and age at symptom onset.
Researcher Kala Mehta, DSc, who is an epidemiologist at the University of California, San Francisco, says she went into the study expecting to find that whites live longer than the other ethnic groups studied following an Alzheimer's diagnosis.
"That was our original hypothesis, but it wasn't what we found," she tells WebMD.
Alzheimer's, Race, and Survival
The study is one of the largest ever to examine the impact of ethnicity on Alzheimer's disease outcomes.
But because it included only patients treated at Alzheimer's disease centers, the findings may not be an accurate indicator of what is happening with the Alzheimer's population at large, Mehta says.
"It is possible that these ethnic differences persist, but we can't say that from this study," she says.
Four out of five (81%) of the study participants were white, 12% were African-American, 4% were Latino, 1.5% were Asian, and 0.5% were American Indian.
The patients were followed for an average of 2.4 years, and they had a median survival of 4.8 years since their first visit to an Alzheimer's disease center.
Autopsy results from 3,000 patients revealed no significant differences in Alzheimer's disease progression at death by racial group.
But while Asians and American Indians lived about as long as whites with Alzheimer's disease, Latinos and African-Americans lived significantly longer.
Mehta says the reasons for this remain a mystery.
"Our goal is to try to understand the racial differences with a view toward improving the health of all people with Alzheimer's disease," she says.
Reasons for Survival Difference Unclear
American Academy of Neurology spokesman David Knopman, MD, tells WebMD that he too was surprised by the study findings.
He says they may point to a genetic difference between the races linked to Alzheimer's survival or they may be driven by cultural differences between the studied ethnic groups.
Whites are more likely to be treated at Alzheimer's centers than blacks and Latinos. Because of this, white patients attending such centers may also be more likely to have other health problems that could affect survival, Knopman says.
Knopman is a professor of neurology at the Mayo Clinic in Rochester, Minn.
"We need more studies to tell us what is going on here," he says. "But one encouraging message from this research is that blacks and Latinos do not seem to be at a disadvantage when it comes to Alzheimer's disease outcomes. That is a very positive finding."