Elevated BP readings at the doctor’s office linked to higher mortality than for those with consistently normal blood pressure.
Evidence for the influence of ambulatory blood pressure on prognosis derives mainly from population-based studies and a few relatively small clinical investigations. This study examined the associations of blood pressure measured in the clinic (clinic blood pressure) and 24-hour ambulatory blood pressure with all-cause and cardiovascular mortality in a large cohort of patients in primary care.
Hypertension in the doctor’s office or elevated blood pressure when someone cuts you off while driving, and other situations that can cause an elevated blood pressure can increase the risk for mortality.
The researchers analyzed data from a registry-based, multicenter, national cohort that included 63,910 adults recruited from 2004 through 2014 in Spain. Clinic and 24-hour ambulatory blood-pressure data were examined in the following categories: sustained hypertension (elevated clinic and elevated 24-hour ambulatory blood pressure), “white-coat” hypertension (WCH) (elevated clinic and normal 24-hour ambulatory blood pressure), masked hypertension (normal clinic and elevated 24-hour ambulatory blood pressure), and normo-tension (normal clinic and normal 24-hour ambulatory blood pressure). Analyses were conducted with Cox regression models, adjusted for clinic and 24-hour ambulatory blood pressures and for confounders.
The results showed that during a median follow-up of 4.7 years, 3,808 patients died from any cause, and 1,295 of these patients died from cardiovascular causes. In a model that included both 24-hour and clinic measurements, 24-hour systolic pressure was more strongly associated with all-cause mortality (hazard ratio, 1.58 per 1-SD increase in pressure; 95% confidence interval [CI], 1.56 to 1.60, after adjustment for clinic blood pressure) than the clinic systolic pressure. Corresponding hazard ratios per 1-SD increase in pressure were 1.55 for nighttime ambulatory systolic pressure and 1.54 for daytime ambulatory systolic pressure. These relationships were consistent across subgroups of age, sex, and status with respect to obesity, diabetes, cardiovascular disease, and antihypertensive treatment. Masked hypertension was more strongly associated with all-cause mortality (hazard ratio, 2.83; 95% CI, 2.12 to 3.79) than sustained hypertension or white-coat hypertension. Results for cardiovascular mortality were similar to those for all-cause mortality.
From the results, they confirmed that ambulatory blood-pressure measurements were a stronger predictor of all-cause and cardiovascular mortality than clinic blood-pressure measurements. White-coat hypertension was not benign, and masked hypertension was associated with a greater risk of death than sustained hypertension. Ambulatory blood-pressure data provides a more comprehensive assessment of blood pressure over the course of a day and have been reported to better predict health outcomes than blood pressure measured in the clinic (clinic blood pressure) or at home. Evidence for the influence of ambulatory blood pressure on prognosis is derived mainly from population-based studies and a few relatively small clinical investigations. However, in these studies, the number of clinical outcomes was limited, which reduced the ability to assess the predictive value of clinic blood-pressure data as compared with ambulatory data. Moreover, the implications of hypertension phenotypes, such as “white-coat” hypertension and masked hypertension, with regard to mortality have remained ill-defined, mainly because of the small number of events reported in previous studies.
Summary of the key results
- 1,295/3,808 patients had cardiovascular-related death.
- All-cause mortality, per 1 standard deviation increase in BP: HR, 1.58 (95% CI, 1.56-1.60) with 24-hour monitoring vs 1.02 (95% CI, 1.00-1.04) with clinic measure.
- All-cause mortality with masked uncontrolled hypertension vs fully controlled hypertension, 24-hour monitoring: HR, 2.61 (95% CI, 2.14-3.17).
- Cardiovascular mortality with masked uncontrolled vs fully controlled hypertension: HR, 2.48 (95% CI, 1.83-3.37).
- All-cause mortality with sustained hypertension, controlled for clinic measure: HR, 1.80 (95% CI, 1.41-2.31).
- All-cause mortality with WCH, controlled for clinic measure: HR, 1.79 (95% CI, 1.38-2.32; P<.001).
- Cardiovascular mortality with WCH, controlled for clinic measure: HR, 1.96 (95% CI, 1.22-3.15; P=.005).
So, you may ask, why does this all matter? It matters because we always measure the patient’s BP when they come into the office and assume that this is their normal blood pressure. But, new BP guidelines call for home monitoring of BP to evaluate WCH (White-coat Hypertension) and 24-hour ambulatory BP measures have already been reported to be more accurate than clinic values.
- Ambulatory systolic BP measurements are tied to both all-cause and cardiovascular mortalities.
- Masked hypertension is associated with greater death risk than sustained hypertension.
- White-coat hypertension is also associated with increased mortality risk.
N Engl J Med 2018; 378:1509-1520; DOI: 10.1056/NEJMoa1712231April 19, 2018