Abstract P324: Hemodynamic Recovery And Baroreflex Sensitivity Are Reliable And Associated With Cardiovascular Disease Risk Factors In A Nationally Representative Sample Of Young US Adults

Abstract

Background: Systolic blood pressure (SBP) usually decreases as heart rate (HR) increases over serial recordings, an autonomic phenomenon mediated by the baroreflex arc and attributed to recovery from stress associated with instrumentation for sphygmomanometry and initial cuff inflation. Despite clinical relevance of baroreflex pathophysiology and widespread availability of simultaneously recorded BP and HR, few epidemiologic studies have examined their relationship, its reliability or population distribution. We therefore investigated the reflex in the National Longitudinal Study of Adolescent Health (Add Health), hypothesizing that it is reliably measured and affected by major cardiovascular disease (CVD) risk factors. Methods: We examined 15,701 U.S. adults aged 24-34 yr (mean = 28.4 yr; 49% female; 34% racial/ethnic minority) at the Add Health Wave IV (2008) in-home visit, which included 3 resting, seated SBPs and HRs recorded at 30 sec intervals. We used random-effects models to estimate SBP recovery (SBPR), HR recovery (HRR), and baroreflex sensitivity (BRS) as the decrease in SBP, increase in HR, and slope of the RR interval-SBP association across recordings. In a stratified, random subset of 100 participants examined twice, 1-2 wk (mean = 8.6 d) apart, we then used random-effects models to estimate their reliability as an intra-class correlation coefficient and 95% confidence interval (ICC, 95% CI) and compare it with HR variability, i.e. the standard deviation of and root mean square of successive differences in RR (SDRR; RMSSD). In the entire sample, we used logistic regression to estimate associations of the measures with CVD risk factors as odds ratios (ORs, 95% CIs). We adjusted estimation parameters for participant clustering, sampling probabilities, and attrition to facilitate inference. Results: The means (SDs) of initial SBP, HR and RR were 127 (15) mmHg, 73 (12) b/min and 841 (141) ms. For SBPR, HRR and BRS, they were -1.2 (4.4) mmHg, 0.6 (4.3) b/min and 0.2 (1.0) ms/mm Hg. The corresponding ICCs (95%CI) were 0.78 (0.70,0.86), 0.47 (0.32,0.63) and 0.63 (0.51,0.75), but only 0.22 (0.03,0.41) and 0.15 (-0.05,0.34) for SDRR and RMSSD. Relative to those without a given CVD risk factor, the OR (95%CI) for BRS < 50th percentile was higher among female, older (> 28 yr), obese (BMI ≥ 30 kg/m2), diabetic (HbA1c ≥ 6.5%), hypertensive (SBP/DBP ≥ 140/90 mm Hg), sedentary and currently smoking participants: 1.7 (1.5,1.8), 1.1 (1.0,1.2), 2.1 (1.9,2.3), 2.3 (1.7,3.0), 1.6 (1.4,1.7), 1.6 (1.4,1.8) and 1.2 (1.1,1.4). Similar associations were observed for SBPR and HRR. Conclusion: Simple, noninvasive measures of hemodynamic recovery and baroreflex sensitivity as estimated from brief recordings of resting, seated SBP and HR are reliable and consistently related to CVD risk factors in young U.S. adults, suggesting potential utility in subclinical assessment of CVD risk.