WASHINGTON — Alzheimer's disease is twice as likely to develop in blacks as it is in whites, and 1.5 times more common among Hispanics, a new national report has found.
The discrepancy appears to stem from a combination of higher rates of chronic illness and lower socioeconomic status in the minority populations, Maria Carrillo, Ph.D., said at a meeting of Alzheimer's disease activists on Capitol Hill.
“We can't pinpoint any known genetic factors as the cause of this discrepancy,” said Dr. Carrillo, the senior director of medical and scientific relations for the Alzheimer's Association, which sponsored the meeting. “Instead, we think this is due to other factors, especially a higher prevalence of hypertension and diabetes in the minority communities, and socioeconomic risks that reduce access to health care.”
The good news, she said in an interview, is that physicians have a chance to identify these risk factors and intervene early, minimizing the effects on cognition.
“Neurologists and general practice physicians need to understand the importance of managing those risk factors. This is key to delaying cognitive decline and perhaps preventing Alzheimer's and other dementias.”
The numbers were drawn from the Alzheimer's Association's report, “2010 Alzheimer's Facts and Figures.” The report based its findings on several national studies of cognitive impairment and Alzheimer's disease in different groups, especially the 2006 Health and Retirement Study (HRS) and the Washington Heights–Inwood Columbia Aging Project (WHICAP).
The HRS study examined the prevalence of cognitive impairment in 16,273 Americans aged 55 years and older. The data can be extrapolated to represent 16 million Americans in that age group, the report noted.
The overall prevalence of cognitive impairment in the study was 11% for those aged 65 years and older. However, whites had the lowest rate (9%). The rate among blacks was 24%, and among Hispanics, 18%.
The discrepancies were higher among younger people. For example, among those aged 55–64 years, blacks were four times more likely to have cognitive impairment than whites; among those aged 85 and older, blacks were twice as likely as whites to have cognitive impairment.
The report also described a similar discrepancy between Hispanics and whites. Among those aged 55–64 years, Hispanics were three times more likely to have cognitive impairment. Among those aged 85 and older, the difference dropped, with Hispanics 1.6 times more likely to have the problem.
The WHICAP study examined rates of Alzheimer's disease and other dementias in a random sampling of 2,126 healthy Medicare beneficiaries aged 65 years and older.
The prevalence of Alzheimer's was 8% in whites, 19% in blacks, and 21% in Hispanics. Again, the differences in prevalence were more pronounced in younger subjects.
According to the report, the HRS study is just one of several that have shown that comorbid hypertension, diabetes, cardiovascular disease, and stroke are more common among people with cognitive impairment than in those with normal cognition.
“It is clear that high blood pressure is more common in African Americans overall and diabetes is more common in both African Americans and Hispanics compared with whites,” the report said. “It is likely that the greater prevalence of these conditions in African Americans and Hispanics than in whites accounts for at least some of the differences among these groups in prevalence of Alzheimer's and other dementias.”
Although Alzheimer's appears more common in both minority groups than in whites, it is much less likely to be formally diagnosed, the report noted. The HRS study showed that 46% of whites with cognitive impairment had a formal diagnosis of a “memory-related disease,” compared with 33% of blacks and 34% of Hispanics.
“This is very worrisome,” Dr. Carrillo said. “It means that these populations are unable to get access to medications that may be able to help them, especially in the early phases of the disease.”
The full report is available at www.alz.org/alzheimers_disease_facts_figures.asp