Association of Variability of Systolic Blood Pressure with Complications and Mortality in Patients with Hypertension

Abstract

Some patients with hypertension tend to have more variability of BP, especially in systolic BP (SBP), than others. It is not known whether clinic visit-to-visit variability (VVV) in SBP increases the risk of complications. Objectives: To evaluate whether the incidence of cardiovascular disease (CVD), chronic kidney disease (CKD) and all-cause mortality was associated with VVV of SBP among hypertensive patients in real-world primary care. Study Design: A retrospective population-based cohort study. Population and Setting: 225,759 Chinese primary care hypertensive patients aged ≥18 years and without prior diagnosis of diabetes mellitus, CVD, or CKD were sampled between October 2011 and March 2012 from a unified electronic medical record system of all public primary care clinics in Hong Kong. All relevant data recorded from October, 2011 to September, 2017 were extracted from the electronic medical records. Outcome Measures and Data Analysis: VVV of SBP was determined by the standard deviations (SD) of SBP recorded during each clinic follow up visit over the years until first occurrence of an event or end of study. Cox regressions adjusted with patients’ baseline characteristics, mean, and temporal trend of SBP were applied to examine the associations between VVV of SBP and incident CVD, CKD, all-cause mortality, and their composite. Subgroup analyses by patients’ characteristics were further conducted. Results: After a median follow-up of 70.5 months (1.2 million person-years), 50,713 (22.5%) subjects had one or more events including 25,714 CVD, 27,603 CKD, and 16,778 deaths. There was a positive continuous association between SBP SD and the risk of CVD, CKD, and mortality among this cohort of hypertensive patients, with no evidence of a threshold. Each 10mmHg increase in SBP SD was associated with 35% (HR: 1.35 [95% CI 1.30-1.39]), 39% (HR: 1.39 [95% CI 1.35-1.43]), 40% (HR: 1.40 [95% CI 1.34-1.45]), and 37% (HR: 1.37 [95% CI 1.34-1.40]) higher risk of CVD, CKD, mortality, and their composite, respectively. HRs were attenuated with older age, mean SBP, Charlson index, and decreased temporal trend of SBP, but they remained significant and consistent. Conclusions: Variability in SBP is a significant risk factor of complications and mortality in primary care hypertensive patients, in addition to baseline and mean achieved SBP. Clinicians should take note of the VVV of SBP and consider intervention to reduce BP fluctuation. Upon completion of this session, participants should be able to: 1.Be aware that variability of systolic blood pressure is a risk factor of hypertensive complications. 2.Replicate a similar study on big clinical data routinely collected in primary care.