Ambulatory BP Beats Clinic BP for Mortality Prediction

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Ambulatory blood pressure measurements are a consistently better predictor of mortality than clinic BP measurements, concludes a study in The New England Journal of Medicine.

The study included 63,910 adult primary care patients enrolled in the national Spanish Ambulatory Blood Pressure Registry from 2004 through 2014. Clinic and 24-hour blood pressure measurements were compared for associations with all-cause and cardiovascular mortality. The researchers also analyzed mortality associations for specific hypertension phenotypes: sustained hypertension (both clinic and ambulatory BP elevated), “white-coat” hypertension (elevated clinic but normal ambulatory BP), masked hypertension (normal clinic but elevated ambulatory BP), and normal BP by both measures.

Fifty-eight percent of cohort members were men; the mean age was 58 years. With a median follow-up of 4.7 years, the analysis included 3808 deaths from any cause and 1295 from cardiovascular causes. In a model including both sets of measurements, 24-hour systolic BP was more strongly associated with all-cause mortality compared to clinic BP: adjusted hazard ratio (HR) 1.58 versus 1.02 per 1-standard deviation increase, respectively. For nighttime and daytime ambulatory systolic BP, adjusted HRs were 1.55 and 1.54, respectively.

Associations with ambulatory BP remained stronger in subgroup analyses by age and sex, obesity, cardiovascular disease, and antihypertensive therapy. By phenotype, the association with all-cause mortality was stronger for masked hypertension (HR 2.83) compared to sustained or white-coat hypertension (HR 1.80 and 1.79, respectively). Cardiovascular mortality showed similar patterns of associations with BP measures.

Based on limited data, ambulatory BP measurements are thought to better predict health outcomes compared to clinic and home measurements. These data from a Spanish national registry show that ambulatory BP measures are more strongly associated with all-cause and cardiovascular mortality compared to clinic-measured BP.

The study also lends insight into the outcomes associated with various BP phenotypes defined by ambulatory and clinic BP. The authors conclude, “White-coat hypertension was not benign, and masked hypertension was associated with a greater risk of death than sustained hypertension” [Banegas JR, et al. Relationship between clinic and ambulatory blood-pressure measurements and mortality. N Engl J Med 2018; 378:1509–1520].