Optimal blood pressure for cognitive function: findings from an elderly African-American cohort study

Abstract

Objectives: To report the results from a prospective cohort study on the association between blood pressure (BP) and cognitive function in elderly African Americans.

Design: Prospective cohort study conducted from 1997 to 2009.

Setting: Community-based study in Indianapolis.

Participants: African Americans aged 65 years or older (N = 3,145).

Measurements: At each assessment, participant cognitive function was measured using the Community Screening Interview for Dementia. Other measurements included BP, height, weight, education level, antihypertensive medication use, alcohol use, smoking, and history of chronic medical conditions.

Results: Longitudinal assessments (n = 5,995) contributed by 2,721 participants with complete independent variables were analyzed using a semiparametric mixed-effects model. Systolic BP (SBP) of approximately 135 mmHg and diastolic BP (DBP) of approximately 80 mmHg were associated with optimal cognitive function after adjusting for other variables (P = .02). Weight loss with body mass index < 30.0 kg/m(2) was significantly related to poorer cognitive performance (P < .001). Older age at first assessment, lower education level; smoking; and history of depression, stroke, and diabetes mellitus were related to worse cognitive function; taking antihypertensive medication and drinking alcohol were associated with better cognitive function.

Conclusion: High and low BP were associated with poorer cognitive performance. A joint optimal region of SBP and DBP for cognitive function has been identified, which may provide useful clinical information on optimal BP control in cognitive health and lead to better quality of life for elderly adults.

Figure 1. Nonlinear effects of continuous variables

Cognitive score as a function of (a) Body mass index (BMI), (b) years of education and (c) age at baseline. Predicted cognitive scores are based on the semiparametric mixed effects regression model while adjusting for sex, blood pressure, antihypertensive medications, alcohol use, smoking status and history of medical conditions. The gray bands denote 95% pointwise confidence intervals.

Figure 2. Bivariate blood pressure effects

Cognitive score as a bivariate function of systolic and diastolic blood pressure. Predicted cognitive scores are based on the semiparametric mixed effects regression model while adjusting for sex, age, body mass index, education level, antihypertensive medications, alcohol use, smoking status and history of medical conditions. Color-coding depicts relatively higher (light grey) and lower (dark) cognitive scores.