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Relationship Between Clinic and Ambulatory BP and Mortality
Quick Takes
- Blood pressure (BP) measures obtained through ambulatory BP monitoring were more informative about the risk of all-cause death or CV death than conventional clinic BPs.
- Masked and sustained hypertension were also associated with an increased risk of death compared with patients with 24-hour BP within normal range.
- This large study further underscores the superiority of ambulatory BP over clinic BP in the association between BP and all-cause death and CV death.
Study Questions:
What are the associations of clinic and 24-hour ambulatory blood pressure (BP) with all-cause and cardiovascular (CV) mortality?
Methods:
The investigators conducted an observational cohort study using clinic and ambulatory BP data obtained from March 1, 2004, to December 31, 2014, from the Spanish Ambulatory Blood Pressure Registry. This registry included patients from 223 primary care centers from the Spanish National Health System in all 17 regions of Spain. Mortality data (date and cause) were ascertained by a computerized search of the vital registry of the Spanish National Institute of Statistics. Complete data were available for age, sex, all BP measures, and body mass index. For each study participant, follow-up was from the date of their recruitment to the date of death or December 31, 2019, whichever occurred first. Cox models were used to estimate associations between usual clinic or ambulatory BP and mortality, adjusted for confounders and additionally for alternative measures of BP. For each measure of BP, we created five groups (i.e., fifths) defined by quintiles of that measure among those who subsequently died.
Results:
During a median follow-up of 9.7 years, 7,174 (12.1%) of 59,124 patients died, including 2,361 (4.0%) from CV causes. J-shaped associations were observed for several BP measures. Among the top four baseline-defined fifths, 24-hour systolic BP was more strongly associated with all-cause death (hazard ratio [HR], 1.41 per 1-standard deviation increment [95% confidence interval, 1.36-1.47]) than clinic systolic BP (1.18 [1.13-1.23]). After adjustment for clinic BP, 24-hour BP remained strongly associated with all-cause deaths (HR, 1.43 [95% CI, 1.37-1.49]), but the association between clinic BP and all-cause death was attenuated when adjusted for 24-hour BP (1.04 [1.00-1.09]). Compared with the informativeness of clinic systolic BP (100%), night-time systolic BP was most informative about risk of all-cause death (591%) and CV death (604%). Relative to BP within the normal range, elevated all-cause mortality risks were observed for masked hypertension (HR, 1.24 [95% CI, 1.12-1.37]) and sustained hypertension (1.24 [1.15-1.32]), but not white-coat hypertension, and elevated CV mortality risks were observed for masked hypertension (1.37 [1.15-1.63]) and sustained hypertension (1.38 [1.22-1.55]), but not white-coat hypertension.
Conclusions:
The authors report that ambulatory BP, particularly night-time BP, was more informative about the risk of all-cause death and CV death than clinic BP.
Perspective:
This analysis reports that BP measures obtained through ambulatory BP monitoring were more informative about the risk of all-cause death or CV death than conventional clinic BP. Furthermore, once 24-hour BP was known, most of the informativeness of clinic systolic BP was lost, whereas associations for ambulatory BP measures were largely unaffected by adjustment for clinic systolic BP. Of note, masked and sustained hypertension were also associated with an increased risk of death compared with patients with 24-hour BP within normal range. Conversely, white-coat hypertension was not associated with increased risk of death. Finally, this large study further underscores the superiority of ambulatory BP over clinic BP in the association between BP and all-cause death and CV death.
Clinical Topics: Diabetes and Cardiometabolic Disease, Prevention, Vascular Medicine, Hypertension
Keywords: Blood Pressure, Blood Pressure Monitoring, Ambulatory, Body Mass Index, Hypertension, Masked Hypertension, Primary Prevention, Risk, Vascular Diseases, White Coat Hypertension
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