The cross-sectional association between blood pressure and Alzheimer's disease in a biracial community population of older persons.

Background: The relation of blood pressure to Alzheimer's disease (AD) is complex because both an association of high blood pressure with increased risk of the disease and lower blood pressure as a consequence of the disease are possible.

Methods: We examined the cross-sectional association of blood pressure and AD in the Chicago Health and Aging Project (CHAP), a study of a geographically defined, biracial community. After in-home interviews with 6.162 residents > or =65 years, a stratified random sample of 729 participants was clinically evaluated; 709 had blood pressures measured, and 243 were diagnosed with AD.

Results: In logistic regression models adjusted for age, sex, education, and race there was no association between blood pressure measured as a continuous variable and Alzheimer's disease. In categorical analyses, however, prevalence of Alzheimer's disease was significantly higher among persons with low systolic pressure (<130 mmHg) compared with the referent group of 130-139 mmHg (odds ratio [OR] = 2.2, 95% confidence interval [CI]: 1.2,4.1), and with low diastolic pressure (<70 mmHg) compared to the referent of 70-79 mmHg (OR = 1.8, 95% CI: I. 1,3.1). High systolic and diastolic categories were not statistically different from the referent group, although there was some evidence that the associations differed by race. The odds ratios changed little with further adjustment for apolipoprotein E genotype, antihypertensive medications, body mass, stroke, diabetes, and heart disease.

Conclusion: These findings are consistent with previous studies showing associations between low blood pressure and AD, but longitudinal studies are needed to characterize cause-and-effect associations.