Time-weighted vs. conventional quantification of 24-h average systolic and diastolic ambulatory blood pressures

José A. Octavio, Jesús Contreras, Pablo Amair, Bernardo Octavio, Domenico Fabiano, Federico Moleiro, Stefano Omboni, Antonella Groppelli, Grzegorz Bilo, Giuseppe Mancia, Gianfranco Parati

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Background: Conventional calculation of mean 24-h ambulatory blood pressure (BP), SBP and DBP based on the average of all BP readings disregards the fact that a larger number of measurements is usually scheduled during the daytime than at night, an imbalance possibly leading to an overestimation of 24-h average BP. The aim of our study was to quantify this possible bias and to explore its determinants. Methods: Four hundred and fifty untreated individuals were subdivided into three groups (150 individuals each) with three different ambulatory blood pressure measurement schedules for day/night: group I, four (day)/two (night) readings/h; group II, four (day)/three (night) readings/h; and group III, with BP readings every 30 min throughout 24 h. Hourly and 24-h averages were computed. The conventional 24-h averages of all SBP and DBP values were compared with the averages of hourly SBP and DBP mean values (time-weighted quantification). The difference between 24-h conventional and 24-h time-weighted BP was computed in each group and related to the degree of nocturnal BP dip and to the ratio between the number of readings of day and night. Result: In the three groups, 24-h conventional and 24-h time-weighted BP values were highly correlated (r > 0.99), 24-h conventional SBP and DBP being significantly higher (P <0.01) than the corresponding 24-h time-weighted values in groups I and II but not in group III (Bland-Altman analysis). The bias magnitude was related to the day/night ratio in number of readings and to nocturnal BP dip in groups I and II (P <0.01) but not in group III. Conclusion: The higher number of readings/h during daytime leads to an overestimation of conventional 24-h average BP, particularly in individuals with preserved nocturnal BP dipping. This can be avoided either by scheduling the same number of readings/h throughout 24 h or by performing a time-weighted quantification of 24-h BP. The clinical implications of these different approaches deserve further investigation.

Original languageEnglish
Pages (from-to)459-464
Number of pages6
JournalJournal of Hypertension
Volume28
Issue number3
DOIs
Publication statusPublished - Mar 2010

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Keywords

  • Ambulatory blood pressure monitoring
  • Average 24-h blood pressure
  • Nocturnal blood pressure fall
  • Time-weighted analysis

ASJC Scopus subject areas

  • Internal Medicine
  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Time-weighted vs. conventional quantification of 24-h average systolic and diastolic ambulatory blood pressures. / Octavio, José A.; Contreras, Jesús; Amair, Pablo; Octavio, Bernardo; Fabiano, Domenico; Moleiro, Federico; Omboni, Stefano; Groppelli, Antonella; Bilo, Grzegorz; Mancia, Giuseppe; Parati, Gianfranco.

In: Journal of Hypertension, Vol. 28, No. 3, 03.2010, p. 459-464.

Research output: Contribution to journalArticle

Octavio, JA, Contreras, J, Amair, P, Octavio, B, Fabiano, D, Moleiro, F, Omboni, S, Groppelli, A, Bilo, G, Mancia, G & Parati, G 2010, 'Time-weighted vs. conventional quantification of 24-h average systolic and diastolic ambulatory blood pressures', Journal of Hypertension, vol. 28, no. 3, pp. 459-464. https://doi.org/10.1097/HJH.0b013e328334f220
Octavio, José A. ; Contreras, Jesús ; Amair, Pablo ; Octavio, Bernardo ; Fabiano, Domenico ; Moleiro, Federico ; Omboni, Stefano ; Groppelli, Antonella ; Bilo, Grzegorz ; Mancia, Giuseppe ; Parati, Gianfranco. / Time-weighted vs. conventional quantification of 24-h average systolic and diastolic ambulatory blood pressures. In: Journal of Hypertension. 2010 ; Vol. 28, No. 3. pp. 459-464.
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AU - Octavio, José A.

AU - Contreras, Jesús

AU - Amair, Pablo

AU - Octavio, Bernardo

AU - Fabiano, Domenico

AU - Moleiro, Federico

AU - Omboni, Stefano

AU - Groppelli, Antonella

AU - Bilo, Grzegorz

AU - Mancia, Giuseppe

AU - Parati, Gianfranco

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N2 - Background: Conventional calculation of mean 24-h ambulatory blood pressure (BP), SBP and DBP based on the average of all BP readings disregards the fact that a larger number of measurements is usually scheduled during the daytime than at night, an imbalance possibly leading to an overestimation of 24-h average BP. The aim of our study was to quantify this possible bias and to explore its determinants. Methods: Four hundred and fifty untreated individuals were subdivided into three groups (150 individuals each) with three different ambulatory blood pressure measurement schedules for day/night: group I, four (day)/two (night) readings/h; group II, four (day)/three (night) readings/h; and group III, with BP readings every 30 min throughout 24 h. Hourly and 24-h averages were computed. The conventional 24-h averages of all SBP and DBP values were compared with the averages of hourly SBP and DBP mean values (time-weighted quantification). The difference between 24-h conventional and 24-h time-weighted BP was computed in each group and related to the degree of nocturnal BP dip and to the ratio between the number of readings of day and night. Result: In the three groups, 24-h conventional and 24-h time-weighted BP values were highly correlated (r > 0.99), 24-h conventional SBP and DBP being significantly higher (P <0.01) than the corresponding 24-h time-weighted values in groups I and II but not in group III (Bland-Altman analysis). The bias magnitude was related to the day/night ratio in number of readings and to nocturnal BP dip in groups I and II (P <0.01) but not in group III. Conclusion: The higher number of readings/h during daytime leads to an overestimation of conventional 24-h average BP, particularly in individuals with preserved nocturnal BP dipping. This can be avoided either by scheduling the same number of readings/h throughout 24 h or by performing a time-weighted quantification of 24-h BP. The clinical implications of these different approaches deserve further investigation.

AB - Background: Conventional calculation of mean 24-h ambulatory blood pressure (BP), SBP and DBP based on the average of all BP readings disregards the fact that a larger number of measurements is usually scheduled during the daytime than at night, an imbalance possibly leading to an overestimation of 24-h average BP. The aim of our study was to quantify this possible bias and to explore its determinants. Methods: Four hundred and fifty untreated individuals were subdivided into three groups (150 individuals each) with three different ambulatory blood pressure measurement schedules for day/night: group I, four (day)/two (night) readings/h; group II, four (day)/three (night) readings/h; and group III, with BP readings every 30 min throughout 24 h. Hourly and 24-h averages were computed. The conventional 24-h averages of all SBP and DBP values were compared with the averages of hourly SBP and DBP mean values (time-weighted quantification). The difference between 24-h conventional and 24-h time-weighted BP was computed in each group and related to the degree of nocturnal BP dip and to the ratio between the number of readings of day and night. Result: In the three groups, 24-h conventional and 24-h time-weighted BP values were highly correlated (r > 0.99), 24-h conventional SBP and DBP being significantly higher (P <0.01) than the corresponding 24-h time-weighted values in groups I and II but not in group III (Bland-Altman analysis). The bias magnitude was related to the day/night ratio in number of readings and to nocturnal BP dip in groups I and II (P <0.01) but not in group III. Conclusion: The higher number of readings/h during daytime leads to an overestimation of conventional 24-h average BP, particularly in individuals with preserved nocturnal BP dipping. This can be avoided either by scheduling the same number of readings/h throughout 24 h or by performing a time-weighted quantification of 24-h BP. The clinical implications of these different approaches deserve further investigation.

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KW - Nocturnal blood pressure fall

KW - Time-weighted analysis

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