TIME-WEIGHTED VS CONVENTIONAL QUANTIFICATION OF 24 HOUR AVERAGE AMBULATORY SYSTOLIC BLOOD PRESSURE (original) (raw)
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Journal of Hypertension, 2004
Objectives To assess quantitatively the relationship between nocturnal blood pressure (BP) fall and 24-h BP variability; to propose a new method for computing 24-h BP variability, devoid of the contribution from nocturnal BP fall; and to verify the clinical value of this method. Methods and results We analysed 3863 ambulatory BP recordings, and computed: (1) the standard deviation (SD) of 24-h BP directly from all individual readings and as a weighted mean of daytime and night-time SD (wSD); and (2) the size of nocturnal BP fall. Left ventricular mass index (LVMI) was assessed by echocardiography in 339 of the patients. The 24-h SD of BP was significantly greater than the 24-h wSD. Nocturnal BP fall was strongly and directly related to 24-h SD, the relationship with 24-h wSD being much weaker and inverse. The difference between SD and wSD was almost exclusively determined by the size of nocturnal BP fall. wSD of systolic BP was significantly related to LVMI, while 24-h SD was not. Conclusion Conventional 24-h SD of BP is markedly influenced by nocturnal BP fall. The weighted 24-h SD of BP removes the mathematical interference from night-time BP fall and correlates better with end-organ damage, therefore it may be considered as a simple index of 24-h BP variability superior to conventional 24-h SD.
The Diurnal Blood Pressure Profile: A Population Study
American Journal of Hypertension, 1992
This population study included 399 subjects, of whom 370 (93%) showed a significant diurnal blood pressure (BP) rhythm. The nocturnal BP fall was normally distributed and averaged 16 ± 9 mm Hg systolic and 14 ± 7 mm Hg diastolic (mean ± SD). The amplitude of the diurnal BP curve followed a positively skewed distribution, with a mean of 16 ± 5 mm Hg for systolic BP and 14 ± 4 mm Hg for diastolic BP. The daily BP maximum occurred at 15:54 ± 4:47 for systolic BP and at 15:11 ± 4:20 for diastolic BP. Thirty-four subjects were reexamined after a median interval of 350 days. The test for the presence of a significant diurnal rhythm was discordant in only two subjects. Repeatability (twice the standard deviation of the differences between paired recordings expressed as a percentage of the mean) varied from 11 to 25% for the 24 h, daytime, and overnight BP, and from 76 to 138% for the parameters describing the diurnal BP rhythm. In nine subjects with an initial night/day ratio of mean BP < 0.78, the nighttime BP was significantly increased at the repeat examination, whereas the opposite tendency was observed in nine subjects with an initial ratio > 0.87. In conclusion, the distribution of the nocturnal BP fall is unimodal. The reproducibility of the ambulatory BP is satisfactory for the level of BP and for the presence of a diurnal BP rhythm, but not for the parameters of the diurnal BP curve. Thus, one 24 h recording is insufficient to fully characterize an individual's diurnal BP profile. Am J Hypertens 1992;5:386-392 KEY WORDS: Ambulatory blood pressure, diurnal blood pressure profile, nocturnal blood pressure fall.
Journal of the American Society of Hypertension, 2008
Although the prognostic value of the day-night blood pressure (BP) changes is established, the most appropriate method for defining day and night is undefined. We assessed the prognostic value of the day-night BP changes by using three definitions of day and night in 2,934 initially untreated hypertensive subjects who underwent 24-hour ambulatory BP monitoring. Over a median follow-up period of 7 years, there were 356 cardiovascular events and 176 deaths. Total cardiovascular events and all-cause mortality were similarly higher in non-dippers (night/day ratio of systolic BP Ͼ10% or Ͼ0%) than in dippers regardless of the definition of day and night. In a receiver-operated characteristic (ROC) curve analysis of the night/day ratio of systolic BP on the occurrence of events, the area under the ROC curve did not differ among the different definitions of day and night (large fixed-clock intervals, narrow fixed-clock intervals, diary) for both total cardiovascular events (0.61 [95% confidence interval (CI): 0.58 to 0.64], 0.61 [95% CI: 0.57 to 0.63], 0.62 [95% CI: 0.58 to 0.65], respectively; P ϭ 0.20) and all-cause mortality (0.65 [95% CI: 0.61 to 0.70], 0.64 [95% CI: 0.60 to 0.69], 0.65 [95% CI: 0.61 to 0.70], respectively; P ϭ 0.78). The prognostic value of the diurnal BP changes is comparable when using different clock-dependent or independent definitions of day and night.
Clinical Significance of the Blood Pressure Changes from Day to Night
Blood pressure (BP) decreases by 10% to 20% from day to night. However, in 25% to 35% of hypertensive subjects there is some reduction in the day-night BP decline. In 3% to 5% of uncomplicated hypertensive subjects there is actually an increase, not a decrease, in BP from day to night. Many studies from independent centers showed that not only left ventricular hypertrophy, but also ventricular arrhythmias, silent cerebrovascular disease, microalbuminuria and progression of renal damage are more advanced in subjects with blunted or abolished fall in BP from day to night than in those with normal day-night BP difference. There is also evidence from longitudinal studies that a blunted, abolished or even reversed BP drop from day to night is associated with an increase in the risk of serious cardiovascular complications. However, if the quantity or quality of sleep is poor during overnight BP monitoring, night-time BP rises and its prognostic significance is no longer reliable. Studies which compared the prognostic value of daytime BP with that of night-time BP inevitably found the superiority of the latter for predicting prognosis. The exciting potential therapeutic implication that the control of night-time BP could be more rewarding, in terms of prevention of cardiovascular disease, than that of daytime BP has yet to be addressed in appropriately designed intervention trials. Of note, 24-hour ABP monitoring is the only practical way to assess the day-night rhythm of BP.
Is blood pressure during the night more predictive of cardiovascular outcome than during the day?
Blood Pressure Monitoring, 2008
The objective of this study was to investigate the prognostic significance of the ambulatory blood pressure (BP) during night and day and of the night-to-day BP ratio (NDR). We studied 7458 participants (mean age 56.8 years; 45.8% women) enrolled in the International Database on Ambulatory BP in relation to Cardiovascular Outcome. Using Cox models, we calculated hazard ratios (HR) adjusted for cohort and cardiovascular risk factors. Over 9.6 years (median), 983 deaths and 943 cardiovascular events occurred. Nighttime BP predicted mortality outcomes (HR, 1.18-1.24; P < 0.01) independent of daytime BP. Conversely, daytime systolic (HR, 0.84; P < 0.01) and diastolic BP (HR, 0.88; P < 0.05) predicted only noncardiovascular mortality after adjustment for nighttime BP. Both daytime BP and nighttime BP consistently predicted all cardiovascular events (HR, 1.11-1.33; P < 0.05) and stroke (HR, 1.21-1.47; P < 0.01). Daytime BP lost its prognostic significance for cardiovascular events in patients on antihypertensive treatment. Adjusted for the 24-h BP, NDR predicted mortality (P < 0.05), but not fatal combined with nonfatal events. Participants with systolic NDR of at least 1 compared with participants with normal NDR ( Z 0.80 to < 0.90) were older, at higher risk of death, but died at higher age. The predictive accuracy of the daytime and nighttime BP and the NDR depended on the disease outcome under study. The increased mortality in patients with higher NDR probably indicates reverse causality. Our findings support recording the ambulatory BP during the whole day.
2014
The association of ambulatory blood pressure (BP) variability with mortality and cardiovascular events is controversial. To investigate whether BP variability predicts cardiovascular events and mortality in hypertension, we analyzed 7112 untreated hypertensive participants (3996 men) aged 52±15 years enrolled in 6 prospective studies. Median followup was 5.5 years. SD of night-time BP was positively associated with age, body mass index, smoking, diabetes mellitus, and average night-time BP (all P<0.001). In a multivariable Cox model, night-time BP variability was an independent predictor of all-cause mortality (systolic, P<0.001/diastolic, P<0.0001), cardiovascular mortality (P=0.008/<0.0001), and cardiovascular events (P<0.001/<0.0001). In contrast, daytime BP variability was not an independent predictor of outcomes in any model. In fully adjusted models, a night-time systolic BP SD of ≥12.2 mm Hg was associated with a 41% greater risk of cardiovascular events, a 55% greater risk of cardiovascular death, and a 59% increased risk of all-cause mortality compared with an SD of <12.2 mm Hg. The corresponding values for a diastolic BP SD of ≥7.9 mm Hg were 48%, 132%, and 77%. The addition of night-time BP variability to fully adjusted models had a significant impact on risk reclassification and integrated discrimination for all outcomes (relative integrated discrimination improvement for systolic BP variability: 9% cardiovascular events, 14.5% all-cause death, 8.5% cardiovascular death, and for diastolic BP variability: 10% cardiovascular events, 19.1% all-cause death, 23% cardiovascular death, all P<0.01). Thus, addition of BP variability to models of long-term outcomes improved the ability to stratify appropriately patients with hypertension among risk categories defined by standard clinical and laboratory variables. (Hypertension. 2014;64:487-493.) • Online Data Supplement (P.V.). The online-only Data Supplement is available with this article at http://hyper.ahajournals.org/lookup/suppl/
Nocturnal blood pressure fall on ambulatory monitoring in a large international database
1997
A wide range of definitions is used to distinguish subjects in whom blood pressure (BP) falls at night (dippers) from their counterparts (nondippers). In an attempt to standardize the definition of nondipping, we determined the nocturnal BP fall and night-day BP ratio by 24-hour ambulatory monitoring in 4765 normotensive and 2555 hypertensive subjects from 10 to 99 years old. In all subjects combined, the systolicldiastolic nocturnal fall and corresponding ratio averaged ('SD)-16.7t 11.01-13.628.1 mm Hg and 87.258.0%183.1f 9.6%, respectively. In normotensive subjects, the 95th percentiles were-0.31-1.1 mm Hg for the nocturnal fall and 99.7%198.3% for the night-day ratio. Both the fall and ratio showed a curvilinear correlation with age. The smallest fall and largest ratio were observed in older (2 7 0 years) subjects. A higher BP on conventional sphygmomanometry was associated with a larger systolic (partial r=.l l) and diastolic (r=.12) nocturnal BP fall. The diastolic (r=.O8) but not the systolic night-day ratio increased with higher conventional BP. The nocturnal BP fall was larger and the corresponding night-day ratio smaller in oscillometric (n=5884) than in auscultatory (n=1436) recordings, in males (n=3730) than in females (n=3590), and in Europe (n=4556) than in the other continents (n=2764). The distributions of the nocturnal BP fall and night
Effect of time of day on intraindividual variability in ambulatory blood pressure
American Journal of Hypertension, 2000
The aim of this study was to determine whether intraindividual blood pressure (BP) variability, measured by noninvasive ambulatory monitoring, differs between the active (daytime) and inactive (nighttime) periods of the day. We obtained ambulatory BP recordings in 143 healthy adults (95 men, 48 women) from Rochester, Minnesota. Readings were obtained every 10 min for a 24-h period. We calculated the
American Journal of Hypertension, 2000
An absent or diminished blood pressure (BP) fall during sleep (so-called "nondipping") has been associated with a higher risk of cardiovascular complications, but the long-term reproducibility of dipper status and the relationship between diurnal changes in BP and perceived sleep quality have not been previously documented in untreated hypertensive patients. Ambulatory BP (ABP) and dipping status were examined in 79 subjects (69 hypertensives and 10 normotensives) at 0, 6, and 12 months. Fifty-six percent of subjects had no change in their dipping status, the majority (53%) dipping normally on all three occasions. However, 44% of patients had variable dipping status, and normal nighttime dipping in BP was observed more often when patients perceived their sleep quality to be good during the period of ABP recording. These results highlight significant intrasubject variability in the diurnal fluctuations in ABP and dipper status, which may in part reflect day-today variations in sleep disturbance during ABP monitoring. Classifying hypertensive patients into dippers or nondippers on the basis of a single ABP recording is unreliable and potentially misleading.