Alzheimer's disease symptom severity in blacks and whites

OBJECTIVE: In order to determine whether there are racial differences in Al zheimer's Disease (AD) symptom severity and vascular comorbidities, we comp ared African-American (black) and Caucasian (white) patients with AD from s imilar socioeconomic backgrounds at the time the disease was first recogniz ed. DESIGN: Cross-sectional observational study from a population-based dementi a registry. PARTICIPANTS: Patients were enrolled from an HMO base population of 23,000 persons more than age 60 in Seattle, Washington. This study examines 453 su bjects with probable AD (38 blacks (mean age 76.5, SD 6.4), and 415 whites (mean age 79.7, SD 6.7)). MEASUREMENTS: Measured were patient demographics, age at onset of AD, AD sy mptom duration, Mini-Mental State Exam (MMSE) score, Blessed Dementia Ratin g Scale, presence of psychiatric symptoms, and vascular comorbidities. RESULTS: Blacks had significantly lower mean cognitive scores (MMSE = 17.2, SD 5.6) compared with whites (MMSE = 20.2, SD 5.2, unpaired t test P < .01 ). The significant racial difference in MMSE scores persisted after control ling for education, duration of AD symptoms, age, and ADL impairment. Black s and whites did not differ significantly regarding gender distribution, ed ucation level, income, or percent with early age of onset of AD. No statist ically significant race-related differences were found in impairments in ac tivities of daily living or symptoms of paranoia, hallucinations, or agitat ion. Blacks had significantly higher rates of hypertension (56%) compared w ith whites (34%) (Fisher's exact test, P = .013), but the rates of stroke a nd ischemic heart disease were similar. CONCLUSIONS: Despite uniform detection methods and controlling for reported duration of dementia symptoms, measured cognitive impairment is significan tly more severe when AD is recognized in blacks compared with whites. The s ignificantly higher prevalence of hypertension among black AD cases was not associated with excess cerebrovascular disease comorbidity. This study hig hlights a need for normative measurements of cognitive function in minority AD groups in order to distinguish differential cognitive symptom severity from possible measurement bias.