Impact of 30- Versus 60-Second Time Intervals Between Automated Office Blood Pressure Measurements on Measured Blood Pressure

Abstract

Guidelines recommend 1 to 2 minutes between repeated, automated office-based blood pressure (AOBP) measures, which is a barrier to broader adoption. Patients from a single hypertension center underwent a 3-day evaluation that included a 24-hour ambulatory blood pressure (BP) monitor (ABPM) and one of two nonrandomized, unattended AOBP protocols. Half of the patients underwent 3 AOBP measurements separated by 30 seconds, and the other half underwent 3 BP measurements separated by 60 seconds. All measurements were compared with the average awake-time BP from ABPM and the first AOBP measurement. We used linear regression to assess whether the 30-second protocol was associated with individual or average AOBP measurements or awake-time ABPM and used an interaction term to determine whether interval modified the relationship between AOBP measurements (individual and mean) with awake-time ABPM. Among 102 patients (mean age, 59.2±16.2 years; 64% women; 24% Black), the average awake-time BP was 132.5±15.6/77.7±12.2 mm Hg among those who underwent the 60-second protocol and 128.6±13.6/76.5±12.5 mm Hg for the 30-second protocol. Mean systolic/diastolic BP was lower with the second and third AOBP measurement by −0.5/−1.7 mm Hg and −1.0/−2.3 mm Hg for the 60-second protocol versus −0.8/−2.0 mm Hg and −0.7/−2.7 mm Hg for the 30-second protocol; protocol did not significantly modify these differences. Differences between AOBP measurements (first, second, or third) and awake-time ABPM were nearly identical across protocols. In conclusion, a 30-second interval between AOBP measurements was as accurate and reliable as a 60-second interval. These findings support shorter time intervals between BP measurements, which would make AOBP more feasible in clinical practice.