Comparison of Alzheimer's disease in American Indians, whites, and African Americans.

Background: The recent development of a national Alzheimer's disease database makes it possible to compare the course of illness in various ethnic groups.

Methods: The National Alzheimer's Coordinating Center database was used to compare the clinical presentation and course of Alzheimer's disease (AD) in American Indians with whites and African-Americans, and to compare findings in American Indians seen in Oklahoma with those seen elsewhere. We ascertained the diagnosis of probable and possible AD, gender, education, history of affected first-degree relative, depression, history of stroke, Parkinson symptoms, age at onset of dementia, initial visit, and death. We also ascertained years from symptom onset and initial evaluation to death, initial Mini-Mental State Exam (MMSE) score adjusted for education, and years from onset of symptoms.

Results: Data from 30,993 subjects were analyzed. There were statistically significant but only small differences between groups. American Indians had the lowest proportion of affected first-degree relatives, depression, and extrapyramidal symptoms. Whites had the highest proportion of subjects with affected first-degree relatives and depression, but the lowest history of stroke. African Americans had the most frequent history of stroke and extrapyramidal symptoms. Indians seen in Oklahoma had a lower proportion of affected first-degree relatives than did those seen elsewhere.

Conclusions: Although there were no clinically significant differences in course of illness between these self-identified ethnic groups, this finding with regard to American Indians must be interpreted with caution, because the subjects for whom we had information regarding ancestry reported a smaller proportion of American Indian (25%) than white (75%) heritage.