Racial differences in the etiology of dementia and frequency of Alzheimer lesions in the brain.

Empirical observations suggest a preponderance of cases of sporadic Alzheimer's disease among whites relative to blacks. If true, this might indicate a genetic basis for non-familial Alzheimer's disease. Among 6,000 consecutive autopsies performed at The Johns Hopkins Hospital, 242 adults with dementia were identified. The 98 consultation cases were excluded from the data analysis because of potential selection bias. Among the remaining 144 cases, the proportions of whites and blacks were similar, yet the frequency of Alzheimer's disease was 2.6 times higher among whites (P = 0.001), dementia due to Parkinson's disease was more frequent among whites (P = 0.05), and the frequencies of multi-infarct dementia and dementia due to chronic ethanol abuse were higher among blacks (P = 0.004 and P = 0.007, respectively). Moreover, in brains from neurologically intact controls, incidental histologic lesions of Alzheimer's disease were observed more frequently in whites than blacks (P = 0.01). These findings provide a strong argument in favor of genetic transmission of sporadic Alzheimer's disease.