Seventeen million American adults with blood pressure that appears normal during a visit to the doctor may have masked hypertension, according to a new study from researchers at Columbia University Medical Center and Stony Brook University School of Medicine.

Masked hypertension occurs in people with normal or pre-hypertensive blood pressure readings in the clinic (at or below 140/90 mm Hg) but high daytime ambulatory readings (average above 135/85 mm Hg). Ambulatory blood pressure is measured with a wearable monitor that takes a blood pressure reading every 15 or 30 minutes, for 24 hours, as the individual goes about normal daily activities.

High blood pressure is a major risk factor for cardiovascular problems, including heart attack and stroke. Prior research has shown that people with masked hypertension have a similar cardiovascular risk as those with high clinic blood pressure. Outside of the United States, researchers have estimated that between 10 percent and 30 percent of adults have masked hypertension. But because national health surveys do not include 24-hour ambulatory blood pressure measurements, it is unknown how many people in the United States have masked hypertension and how they can be identified.

Researchers also confirmed prior studies showing that masked hypertension was more common in males, individuals age 45 years or older, and those with diabetes and pre-hypertension (120/80 mm Hg to 139/89 mm Hg).

“While it may not be practical to perform 24-hour blood pressure monitoring on all adults who have normal clinic blood pressure, our study suggests that it may be prudent to screen men 45-plus years of age with diabetes or prehypertension,” said lead investigator Joseph E. Schwartz, PhD, professor of psychiatry and sociology at Stony Brook University School of Medicine and a lecturer at Columbia University Medical Center.

Source: Columbia University Medical Center: