Ambulatory vs. Clinical BP: Which is More Informative For All-Cause and CV Mortality?

Blood pressure (BP) measures obtained through ambulatory BP monitoring are more informative about the risk of all-cause or cardiovascular (CV) mortality than conventional clinical BP, according to a study published May 5 in Lancet.

Natalie Staplin, PhD, et al., 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 to determine the association between clinic and 24-hour ambulatory BP and all-cause and cardiovascular mortality. The registry included patients from 223 Spanish National Health System primary care centers in all 17 regions of Spain. For each study participant, follow-up was from the date of recruitment to the date of death or Dec. 31, 2019, whichever occurred first. For each measure of BP, five groups were created defined by quintiles of that measure among patients who died.

Results showed that over the median follow-up of 9.7 years, 7,174 (12.1%) of the 59,124 study patients died, including 2,361 (4.0%) from cardiovascular causes. In addition, among the top four baseline-defined quintiles, 24-hour systolic BP compared with clinic systolic BP was more strongly associated with all-cause death (hazard ratio [HR], 1.41 per 1-standard deviation increment; 95% CI, 1.36-1.47 vs. HR, 1.18 per 1-standard deviation increment; 95% CI, 1.13-1.23). After adjustment for clinic BP, 24-hour BP remained strongly associated with all-cause death (HR, 1.43; 95% CI, 1.37-1.49), but this association was attenuated when adjusted for 24-hour BP (HR, 1.04; 95% CI, 1.00-1.09).

Researchers note that compared with the informativeness of clinic systolic BP, night-time systolic BP was most informative about the risk of all-cause death and cardiovascular death. They note that “the relative informativeness of 24-h ambulatory systolic BP for risk of death was almost five times greater than clinic systolic BP,” and that night-time systolic BP was about six times more informative for death than clinic BP and nearly twice as much than daytime systolic BP.

Notably, the risk of mortality was higher with masked hypertension and sustained hypertension, but not white coat hypertension. Compared with BP within the normal range, the hazard ratios for all-cause mortality were 1.24 for both masked hypertension and sustained hypertension, and for cardiovascular mortality they were 1.37 and 1.38, respectively.

They write, “The dominance of the association of night-time blood pressure with death confirms some previous reports and is striking, highlighting a need to both evaluate and control night-time blood pressure, particularly in higher risk patients. The risk of death associated with masked hypertension is concerning as these patients usually remain undetected with screening using clinic blood pressure alone.”

Clinical Topics: Diabetes and Cardiometabolic Disease, Prevention, Vascular Medicine, Hypertension

Keywords: Registries, Hypertension, White Coat Hypertension, Reference Values, Blood Pressure Monitoring, Ambulatory, Masked Hypertension

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