Reason for their added survival remains unclear, scientists say
WEDNESDAY, Nov. 14 (HealthDay News) -- Blacks and Hispanics appear to live longer following an Alzheimer's diagnosis than white patients, a new study suggests.
While men and women of Asian and American Indian descent diagnosed with the disease were found to have survival expectancies equivalent to that of white Alzheimer's patients, patients of Hispanic or black ethnicity were found to live 40 percent and 15 percent longer, respectively.
The observation held up even after accounting for a wide range of factors -- including age, gender, and living environment -- that could influence post-diagnosis longevity.
"This study didn't address all of the reasons why, and there's a lot more work that needs to done in this area, but we found that African-Americans and Latinos with Alzheimer's lived on average longer than white patients with Alzheimer's," said study lead author Kala M. Mehta, an assistant adjunct professor at the University of California, San Francisco.
"We were surprised by the finding," she added. "In fact, we had hypothesized that it would be in the other direction. So, now we're hoping to do more research in the area of racial and ethnic differences and cognitive decline in Alzheimer's to get at the reasons for why differences occur."
Mehta and her team reported their findings in the Nov. 14 online issue of the journal Neurology.
According to the Alzheimer's Association, more than five million Americans now have Alzheimer's. The study team pointed out that by 2050, estimates suggest that more than three million Alzheimer's patients will be of non-white origin.
Currently, the disease ranks seventh among causes of death in the United States.
To assess potential differences in Alzheimer's outcome among races, Mehta and her team analyzed data collected between 1984 and 2005 at more than 30 Alzheimer's Disease Centers (ADCs) across the United States. ADCs are standardized Alzheimer's care facilities funded by the U.S. National Institute on Aging, many of which are affiliated with local universities.
The study was large, including information on more than 31,000 men and women aged 65 and older, all of whom had received a possible or probable Alzheimer's diagnosis.
Patient ethnicity, race, age, gender, educational background, marital status, living situation, and cognitive function scores were recorded at initial diagnosis, as was the first subsequent evidence of dementia onset.
The authors reported that 81 percent of the patients were white, 12 percent were black, 4 percent were Hispanic, and 1.5 percent were Asian.
The average patient age was about 78, and 65 percent were women.
During the observation period, patients lived an average of 4.8 years following diagnosis, and almost 39 percent of the patients died. Autopsies were conducted on 3,000 of the deceased.
Overall, deaths were more common among patients who were older, male, and had poorer initial cognitive skills scores.
With respect to race and ethnicity, the research team found that white patients were more likely to die than patients of other backgrounds. The death rate was 41 percent among whites compared to 30 percent among blacks and 21 percent for Hispanics.
After accounting for all the demographic factors that might influence outcome, the researchers concluded that black and Hispanic Alzheimer's patients had a lower risk for mortality than their white counterparts.
Mehta and her colleagues stressed, however, that the pool of ADC patients examined was not necessarily representative of U.S. Alzheimer's patients as a whole. Most patients received care outside the confines of a government-funded medical center, she said, and as such they would presumably have received a much more varied, non-standardized level of care.
The researchers cautioned, therefore, that the findings might not be applicable to all Alzheimer's patients.
Just why blacks and Hispanic patients live longer with Alzheimer's remains unclear, Mehta said.
"For example, we might consider the differing amounts of social support from family members in the differing ethnic groups," she observed. "And also the different amounts of other diseases found in these patients, and the treatment of those other diseases, which could be different between groups."
"But what's really important here is that, if we do find the underlying factors that account for the differences, we might be able to improve survival for patients, regardless of their race," she added.
Greg M. Cole is a neuroscientist with the Greater Los Angeles VA Healthcare System and an associate director with the Alzheimer's Disease Research Center in the David Geffen School of Medicine at the University of California, Los Angeles. He expressed surprise at the study results.
"In general, things run in the opposite direction for some pretty well-understood reasons," he noted. "That black and Latino populations as a group have less access to health care, more metabolic syndrome, more cardiovascular risk factors putting them at risk for earlier mortality, lower socio-economic backgrounds, a lot of hypertension, diabetes, and these sorts of things. So, we're accustomed to seeing more rapid decline and more mortality and shorter life expectancy among those minorities."
Cole agreed with Mehta that most probably a complex combination of genetic, cultural, and routine health care differences would account for the mortality spread.
"But there's all kind of heterogeneity among populations, and much more investigation will be needed to get at the cause," he added.
Find out more on Alzheimer's disease at the Alzheimer's Association.
SOURCES: Kala M. Mehta, DSc, assistant adjunct professor, University of California, San Francisco; Greg M. Cole, Ph.D., neuroscientist, Greater Los Angeles VA Healthcare System, and associate director, Alzheimer's Disease Research Center, David Geffen School of Medicine, University of California, Los Angeles ; Nov. 14, 2007, online issue, Neurology.
All rights reserved