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Clinic blood pressure readings tended to underestimate -- rather than overestimate -- average daily blood pressure among working adults, according to the Masked Hypertension study.
At 123/77.4 mm Hg, mean ambulatory blood pressure during waking hours exceeded the average clinical reading of 116/75.4 mm Hg, reported Joseph E. Schwartz, PhD, of Stony Brook University, and colleagues online in Circulation.
Ambulatory readings that exceeded clinical readings by more than 10 mm Hg were more common than vice versa, which was especially true for young adults and those with normal BMIs. According to the authors, 15.7% of patients with non-elevated clinic blood pressure readings had masked hypertension.
"A substantial number of otherwise healthy individuals have masked hypertension that may warrant treatment or at least monitoring," they wrote wrote.
At older ages, and higher BMIs, the difference in systolic pressure diminished without disappearing completely. For diastolic pressures, the difference between methodologies vanished by age 65, while for those with BMI over 32.5 kg/m2, it was actually more common for clinic readings to exceed ambulatory ones.
"The physician's dilemma is that she/he knows only the patient's clinic blood pressure, but it is the ambulatory blood pressure that is most prognostic," according to Schwartz's group.
"Knowing that if the patient is young or has a low BMI, his/her ambulatory blood pressure is likely to be considerably higher than the clinic blood pressure could inform the decision of whether to recommend a 24-hour ambulatory blood pressure monitoring. On the other hand, if the patient is 60 years old and mildly obese, then the clinic blood pressure may be relatively unbiased."
"I do agree that many patients have higher daytime home or ambulatory blood pressure levels than their clinic blood pressure," William C. Cushman, MD, of University of Tennessee Health Science Center in Memphis, told MedPage Today, citing similar results from SPRINT and an ACCORD substudy.
Clinical trials need to show whether those with masked hypertension can benefit from drug treatment, he argued. This is a group that has "never been included in outcome trials before so we don't really know the answer, but it makes sense they would benefit since they are at higher risk."
"For now, we should pay attention to any home or ambulatory blood pressure information we have on patients ... but I believe it is premature to recommend we base our treatment primarily on home or ambulatory blood pressure monitoring," Cushman said.
In any case, "it is important to take blood pressure correctly in the office," he emphasized. "Virtually no usual practices do, and they should."
The Masked Hypertension study included 888 patients who were healthy and employed (average age 45 years, 59% women) by Stony Brook University, Columbia University, their affiliated hospitals, or a private hedge fund management company.
None had cardiovascular disease. They were screened in if their blood pressure was less than 160/105 mm Hg without antihypertensives.
Nine clinical blood pressure readings were taken over three visits and averaged, which was compared to a 24-hour ambulatory blood pressure recording.
"Importantly, the number of individuals >65 years of age in our sample was small, and by design, all such individuals were employed," the investigators wrote. "Further research is needed to determine whether this pattern would hold in other samples of employed individuals (i.e., in other types of occupations and organizations, or outside the New York metropolitan area), or in a representative sample of employed, non-employed, and retired individuals."
Ambulatory blood pressure was measured on only one day too, commented William A. Zoghbi, MD, of Houston Methodist DeBakey Heart & Vascular Center, and former president of the American College of Cardiology.
"The type and environment of daily activity may also have influenced the results: all individuals were employed in either a hospital/university setting or worked in a hedge fund, where stress during the day may be higher than in the general or older population," according to Zoghbi in an interview with MedPage Today.
"Importantly, this study has alerted clinicians that hypertension can be masked in employed young and middle-aged adults with borderline blood pressure in the clinic. Further studies are needed to clarify whether these observations are seen in hypertensive patients, on or off treatment, and in older individuals, and the clinical outcome of such patients."
Schwartz and Zoghbi disclosed no competing interests.
Cushman reported receiving institutional grants from Lilly and performing uncompensated consulting to Takeda.
- Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner