Continuous blood pressure variability within young, healthy adults: a test-retest study to assess relative and...

Variability in 24-h and visit-to-visit blood pressure (BP) has been reported to be predictive of adverse cardiovascular outcomes. Although recent studies have used beat-to-beat blood pressure variability (BPV) as a predictor of cardiovascular risk, the reliability of beat-to-beat BPV remains equivocal. The purpose of this study was to examine the intraindividual reliability of BPV and to compare that reliability to more widely documented heart rate variability (HRV) in young healthy adults. Continuous heart rate (HR, electrocardiogram), beat-to-beat blood pressure (BP, finger plethysmography), and respiratory rate (pneumobelt) were recorded during 10 min of rest in 77 participants [38 males and 39 females; age: 23 ± 5 yr; body mass index (BMI): 25 ± 4 kg·m^-2] on two occasions separated by ≥2 days (25 ± 19 days; 2-98 days). Reliabilities of beat-to-beat BPV, HRV (time- and frequency-domain), and additional cardiovascular (heart rate, blood pressure) assessments were quantified as relative and absolute reliability using the intraclass correlation coefficient (ICC) and the coefficient of variation (CoV), respectively. Beat-to-beat BPV demonstrated moderate relative and good absolute reliability (10-min duration: ICC = 0.601-0.684, CoV = 14%-16%). In contrast, relative reliability of time-domain HRV was good-to-excellent, whereas absolute reliability was poor-to-good (10-min duration: ICC = 0.844-0.904, CoV = 13%-34%). Frequency-domain HRV demonstrated moderate to excellent relative reliability and poor absolute reliability (10-min duration: ICC = 0.626-0.903, CoV = 34%-37%). In summary, the rigor and reliability of continuous BPV and HRV are different when parsed out by relative versus absolute reliability, with relative reliability being stronger with HRV and absolute reliability being stronger with BPV. These findings suggest both caution and specificity when using continuous BPV or HRV for cardiovascular disease (CVD) risk-stratification purposes.NEW & NOTEWORTHY Beat-to-beat blood pressure variability (BPV) has gained attention as a noninvasive predictor of cardiovascular disease. However, the reliability of BPV has not been adequately characterized. We investigated the intraindividual reliability of beat-to-beat BPV and compared that reliability to more traditional heart rate variability (HRV). BPV demonstrated higher absolute, but lower relative, reliability compared with HRV. These findings suggest a need for caution and specific reporting when using continuous BPV or HRV for cardiovascular risk-stratification purposes.