Commentary | Published:

The relationship between systolic and diastolic pressures: a possible link between risk-related clinical measures and arterial properties

Hypertension Research volume 33, pages 657658 (2010) | Download Citation

The systolic–diastolic pressure relationship

Repeated measurements of systolic blood pressure (SBP) and diastolic blood pressure (DBP) frequently show a highly linear relationship. This phenomenon was observed in the Framingham study over a 14-year period using office blood pressure (BP) measurement, in-home BP monitoring over a few weeks, 24-h ambulatory blood pressure measurement (ABPM) and beat-by-beat BP monitoring over a few minutes. The standard statistical measures of this linear relationship are the regression slope and the SBP–DBP correlation coefficient r. The currently used slope-related measures are (a) the regression slope obtained by treating the DBP as an independent variable, hereafter called the S–D slope, after Gavish et al.,1 and (b) one minus the regression slope, calculated by treating the SBP as the independent variable, called the Arterial Stiffness Index (ASI), after Li et al.2 However, the determination of slope-related measures using standard regression leads to artifactual dependence on r; that is, the slope becomes dependent on the degree of data scattering. The reason for this is that the SBP and the DBP are measured simultaneously, and neither variable can be described as ‘dependent’ or ‘independent’. This problem is eliminated by using ‘symmetric regression’, which handles both variables in a symmetrical way.1, 3 Figure 1 demonstrates why this issue becomes important when attempting to estimate slope-related measures.

Figure 1
Figure 1

The relationship between the slope-related measures of the ASI and the S–D slope when calculated for individual patients by different regression methods using the 24-h ABPM data of 3703 subjects (analysis performed with the permission of Dr Michael Bursztyn). The dashed-line contours represent the theoretical relationship between the two measures for a given value of the SBP–DBP correlation coefficient r (data were analyzed with the permission of Dr Michael Bursztyn). With symmetric regression, the ASI equals 1−1/(S–D slope), making both measures equivalent.

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  1. InterCure Ltd., The Geophysical Institute Building, 6 Haba'al Shem-Tov Street, Northern Industrial Area, Lod 71289, Israel

    • Benjamin Gavish

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Correspondence to Benjamin Gavish.

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https://doi.org/10.1038/hr.2010.97

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