Association of arterial stiffness and blood pressure variability with silent brain lesions in healthy hypertensive elderly Chinese

Abstract

Silent brain lesions (SBLs) are frequently detected in elderly subjects with hypertension. Although without apparent stroke symptoms, they are related to high risks of stroke and dementia. Arterial stiffness and visit-to-visit blood pressure variability (BPV) are two non-invasive clinical indicators that are associated with increased risks of stroke and other cardiovascular events. However, the associations of them with SBLs and cognitive function in elderly hypertensive subjects are still unclear.

This thesis was aimed to 1) investigate the prevalence and risk factors of SBLs; 2) to study the associations of arterial stiffness with SBLs and cognitive impairment; and 3) to evaluate the associations of visit-to-visit-BPV with SBLs and cognitive impairment in generally healthy hypertensive elderly Chinese. Elderly Chinese subjects were recruited from the general out-patient clinic if they had a history of hypertension for ≥ 5 years and no history of stroke, dementia or cardiovascular diseases. All subjects underwent a 3.0 T magnetic resonance imaging examination of the brain. Four types of SBLs were rated, including silent brain infarcts (SBIs), brain microbleeds (BMBs), periventricular hyperintensity (PVH) and deep white matter hyperintensity (DWMH). Cognitive impairment was assessed by the Montreal Cognitive Assessment (MoCA) scale. Brachial-ankle pulse wave velocity (baPWV), a valid indicator of arterial stiffness, was measured using the Omron PWV / ABI device. Previous office blood pressure measurements were collected for the calculation of visit-to-visit BPV parameters, which included the standard deviation, coefficient of variation, successive variation and variation independent of mean blood pressure.

Among 349 patients, 16.3 % had SBIs, 22.9 % had BMBs, 8.6 % had severe PVH and 4.0 % had severe DWMH. The following associations between clinical factors and SBL subtypes were found to be significant in statistical analyses: 1) smoking, high pulse pressure and low fasting glucose with SBIs; 2) high pulse pressure and high-density lipoprotein cholesterol with BMBs; 3) age with the severity of PVH and DWMH. Age, pulse pressure, PVH and lobar BMBs were significantly associated with cognitive impairment.

baPWV predicted severe PVH independent of age and blood pressure levels. The highest quartile of baPWV was associated with a 2.5- to 3-fold increased risk of severe PVH. No significant association was found between baPWV and other SBLs. High baPWV was significantly related to cognitive impairment. Systolic BPV and pulse pressure variability were predictive of the severity of PVH. Systolic BPV were associated with the severity of DWMH. No significant relationship was found between BPV and other SBLs. Pulse pressure variability was significantly higher in those presented with cognitive impairment. In addition, baPWV and systolic BPV were significantly correlated with each other. In summary, this thesis provided evidences regarding the prevalence of SBLs, and the predictive value of arterial stiffness and visit-to-visit BPV for SBLs and cognitive impairment. Arterial stiffness and visit-to-visit BPV may serve as useful clinical measurements for the prediction of severe white matter hyperintensity in healthy hypertensive elderly Chinese.