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.
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.
Authors: Marwah Abdalla; Swati Sakhuja; Oluwasegun P Akinyelure; S Justin Thomas; Joseph E Schwartz; Cora E Lewis; James M Shikany; Donald Lloyd-Jones; John N Booth; Daichi Shimbo; Martica H Hall; Paul Muntner Journal: J Hypertens Date: 2021-12-01 Impact factor: 4.776
Authors: John N Booth; D Edmund Anstey; Natalie A Bello; Byron C Jaeger; Daniel N Pugliese; Stephen Justin Thomas; Luqin Deng; James M Shikany; Donald Lloyd-Jones; Joseph E Schwartz; Cora E Lewis; Daichi Shimbo; Paul Muntner Journal: J Clin Hypertens (Greenwich) Date: 2019-02-05 Impact factor: 3.738
Authors: Anthony O Etyang; Christopher Khayeka-Wandabwa; Sailoki Kapesa; Esther Muthumbi; Emily Odipo; Marylene Wamukoya; Nicholas Ngomi; Tilahun Haregu; Catherine Kyobutungi; Metrine Tendwa; Johnstone Makale; Alex Macharia; J Kennedy Cruickshank; Liam Smeeth; J Anthony G Scott; Thomas N Williams Journal: J Am Heart Assoc Date: 2017-04-05 Impact factor: 5.501
Authors: Anthony O Etyang; Ben Warne; Sailoki Kapesa; Kenneth Munge; Evasius Bauni; J Kennedy Cruickshank; Liam Smeeth; J Anthony G Scott Journal: J Am Heart Assoc Date: 2016-12-15 Impact factor: 5.501
Authors: S Justin Thomas; John N Booth; Byron C Jaeger; Demetria Hubbard; Swati Sakhuja; Marwah Abdalla; Donald M Lloyd-Jones; Daniel J Buysse; Core E Lewis; James M Shikany; Joseph E Schwartz; Daichi Shimbo; David Calhoun; Paul Muntner; Mercedes R Carnethon Journal: J Am Heart Assoc Date: 2020-03-19 Impact factor: 5.501
Authors: Anthony O Etyang; Christopher K Wandabwa; Sailoki Kapesa; Esther Muthumbi; Emily Odipo; Marylene Wamukoya; Nicholas Ngomi; Tilahun Haregu; Catherine Kyobutungi; Thomas N Williams; Johnstone Makale; Alex Macharia; J Kennedy Cruickshank; Liam Smeeth; J Anthony G Scott Journal: Am J Epidemiol Date: 2018-02-01 Impact factor: 4.897