A study of patients with Alzheimer's disease indicates that Latinos and African Americans survive longer with the disease than whites. The study was led by scientists at the San Francisco VA Medical Center and the University of California, San Francisco.
The study of more than 30,000 patients aged 65 and older at designated Alzheimer's disease clinics around the country showed that Latinos were likely to live almost fifty percent longer than whites after a diagnosis of Alzheimer's disease, while African Americans were likely to survive 15 percent longer.
The study authors found that common risk factors such as patients' age, gender, education, geographic area, type of residence (home, residential facility, or nursing home), and marital status did not explain survival differences between the race and ethnic groups.
The study was published on Nov. 14, 2007 in the online edition of Neurology.
Reasons for the Association Between Race and Survival Remain Unknown
Investigation into the exact reasons for the association between race and survival was beyond the scope of the study, emphasizes lead author Kala M. Mehta, DSc, a geriatrics researcher at SFVAMC and assistant professor of geriatrics at UCSF. "Possible reasons why race seemed to be a factor are complex. They may include cultural differences or genetics. We examined some of these factors, but more thorough research is needed," she says. "If we begin to understand why this difference exists, we can begin to understand how to better care for patients of all races and ethnicities with Alzheimer's."
The researchers analyzed data on 30,916 Alzheimer's patients compiled from 1984 to 2005 at more than 30 Alzheimer's Disease Research Centers, which are specialized clinical research centers funded by the National Institute on Aging. Nineteen percent of patients were nonwhite: 15 percent African American, 4 percent Latino, 1.5 percent Asian, 0.5 percent American Indian, and 1 percent of another race or ethnicity.
The authors measured the mortality risk for each ethnic group over the course of the study. With whites' risk set at 1.00 for reference, Latino risk was 0.57 and African American risk was 0.85. Mortality risk for Asians, American Indians, and others was essentially the same compared with that of whites.
Extent of Disease at Death Is No Less Severe for Members of Different Ethnic Groups
The researchers also analyzed autopsy reports for a subset of 3,017 patients who had given permission to be autopsied, and found no differences in brain pathology between members of different ethnic groups. "It does not appear as if the people of minority ethnicity had less severe brain disease when they died," Mehta observes. "For this subset, it seems they were living longer for other reasons."
While it is premature to extrapolate those reasons, two factors in particular bear further investigation, she says. "It's possible that measurement issues, and misclassification as a result of measurement, could have been part of the reasons for these findings. In fact, my colleagues and I are currently working on the measurement of cognitive functioning in different ethnic groups to find out how measurement may affect diagnosis."
Another possible variable is the role of family caregivers, Mehta says. "We know from the patients' records who their official caregivers were, but we don't know their level of involvement or what care decisions they made. Family caregiver involvement may well differ between different ethnic groups in the United States, but we could not address this in this study."
Mehta adds that possible genetic differences in the molecular or cellular basis of Alzheimer's degeneration might present another potential line of investigation. However, she says, "I think that a lot more research would need to be conducted on the mechanisms of degeneration before this would be clear."
Study Data "Are Not Representative of the Population at Large"
She cautions that the study data "are not representative of the population at large. We don't know the extent to which patients who are seen in these highly specialized Alzheimer's Disease Research Centers differ from the general population. This will be an important difference to study as well."
Co-authors of the study are senior author Kristine Yaffe, MD, of SFVAMC and UCSF; Eliseo J. Pérez-Stable, MD, and Anita Stewart, PhD, of UCSF; Deborah Barnes, PhD, of SFVAMC and UCSF; Brenda Kurland, PhD, of Fred Hutchinson Cancer Research Center, Seattle; and senior author Bruce L. Miller, MD, of UCSF.
The research was supported by funds from the National Institute on Aging, the National Alzheimer's Coordinating Center, the Resource Centers for Minority Aging Research Program, and the Aging and Disability Resource Center. Some of the funds were administered by the Northern California Institute for Research and Education.