Ambulatory blood pressure using 60 rather than 20-min intervals may better reflect the resting blood pressure

Twenty-four hours of ambulatory blood pressure monitoring (ABPM) is recommended in several guidelines as the best method for diagnosing hypertension. In general, the prognostic value of ABPM is superior to single office blood pressure (BP) measurements. Unfortunately, some patients experience considerable discomfort during frequently repeated forceful cuff inflations. In this study we investigated the difference in mean daytime systolic BP (SBP) between low-frequency ABPM (LF-ABPM), measuring once every hour, and high-frequency ABPM (HF-ABPM), measuring three times an hour during daytime, and two times an hour during night-time. Seventy-one patients were included in the analysis. All included patients had an HF-ABPM performed first and within a few weeks they underwent an LF-ABPM. The average day time difference in SBP between the two frequencies was 3.8 mmHg (p-value = 0.07) for mild, 8.2 mmHg (p-value < 0.01) for moderate and 15 mmHg (p-value < 0.001) for severe hypertension. A similar pattern was seen for night-time SBP. This study suggests that mean BP is similar between the two measuring frequencies for normotensive and mild hypertensive patients, while HF-ABPM results in a higher 24-h mean BP for moderate- and severe hypertensive patients. LF-ABPM may more correctly reflect the resting blood pressure in patients with moderate and severe hypertension.