A U-shaped Association Between Blood Pressure and Cognitive Impairment in Chinese Elderly

Abstract

Objectives: Higher or lower blood pressure may relate to cognitive impairment, whereas the relationship between blood pressure and cognitive impairment among the elderly is not well-studied. The study objective was to determine whether blood pressure is associated with cognitive impairment in the elderly, and, if so, to accurately describe the association.

Design: Cross-sectional data from the sixth wave of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) conducted in 2011.

Setting: Community-based setting in longevity areas in China.

Participants: A total of 7144 Chinese elderly aged 65 years and older were included in the sample.

Measures: Systolic blood pressures (SBP) and diastolic blood pressures (DBP) were measured, pulse pressure (PP) was calculated as (SBP) - (DBP) and mean arterial pressures (MAP) was calculated as 1/3(SBP) + 2/3(DBP). Cognitive function was assessed via a validated Mini-Mental State Examination (MMSE).

Results: Based on the results of generalized additive models (GAMs), U-shaped associations were identified between cognitive impairment and SBP, DBP, PP, and MAP. The cutpoints at which risk for cognitive impairment (MMSE <24) was minimized were determined by quadratic models as 141 mm Hg, 85 mm Hg, 62 mm Hg, and 103 mm Hg, respectively. In the logistic models, U-shaped associations remained for SBP, DBP, and MAP but not PP. Below the identified cutpoints, each 1-mm Hg decrease in blood pressure corresponded to 0.7%, 1.1%, and 1.1% greater risk in the risk of cognitive impairment, respectively. Above the cutpoints, each 1-mm Hg increase in blood pressure corresponded to 1.2%, 1.8%, and 2.1% greater risk of cognitive impairment for SBP, DBP, and MAP, respectively.

Conclusion: A U-shaped association between blood pressure and cognitive function in an elderly Chinese population was found. Recognition of these instances is important in identifying the high-risk population for cognitive impairment and to individualize blood pressure management for cognitive impairment prevention.

Keywords: Blood pressure; cognitive impairment; curvilinear association; elderly; hypertension; hypotension.

Figure 1. Smoothing component for cognitive impairment

Legends: Associations of SBP, DBP, PP and MAP with cognitive impairment for the elderly, Chinese Longitudinal Healthy Longevity Survey, China, 2011. The lines depict the estimated function of SBP, DBP, PP and MAP respectively, for risk of cognitive impairment among the elderly, and the shaded area indicates the 95% confidence intervals. SBP, Systolic blood pressure; DBP, diastolic blood pressures; PP, pulse pressure; MAP, mean arterial pressure.