On Sept. 9, 2020, the National Institutes of Health (NIH) announced that after nearly 15 years on an upward trend, awareness among Americans about high blood pressure and how to control and treat it has begun to decline, according to a newly published study. Even with the help of blood pressure medications, some groups, including older adults, are less likely than they were in earlier years to adequately control their blood pressure, the research found.

The study, funded by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, appears in JAMA. The authors say the trend could make longstanding efforts to fight heart disease and stroke—leading causes of death in the United States—even more challenging. High blood pressure, also called hypertension, is a major risk factor for heart disease. According to the Centers for Disease Control and Prevention (CDC), nearly 108 million Americans have hypertension, with a blood pressure reading of 130/80 millimeters of mercury (mm Hg) or higher or are taking medication for their blood pressure, but only 27 million are considered to have their blood pressure under control, despite it being a condition that can be managed.

The study included 18,262 U.S. adults age 18 and older, with high blood pressure. The definition of hypertension at the time of the study was defined by a blood pressure reading of 140/90 mm Hg or higher or by treating the condition with blood pressure medications. Participants with a blood pressure reading of less than 140/90 mm Hg were categorized as having controlled blood pressure.

With data from the National Health and Nutrition Examination Survey (NHANES) taken between1999 and 2018, the study authors looked at 20-year trends in high blood pressure awareness and treatment and blood pressure control. The CDC’s National Center for Health Statistics conducts NHANES.

At the beginning of the survey, participants had their blood pressure measured three times, then averaged. Participants answered yes or no when asked if their doctors told them they had high blood pressure and if they currently took prescribed medication for high blood pressure.

The authors found that in 1999-2000, just 70% of participants showed an awareness of their condition. That number increased steadily to 85% in 2013-2014, but declined to 77% in 2017-2018. Of those “aware” adults, the number who also were taking blood pressure medications remained relatively consistent—85% in 1999-2000, 89% in 2013-2014, and 88% in 2017-2018.

Of all adults with high blood pressure, the number who managed to control their condition increased from 32% in 1999-2000 to 54% in 2013-2014, but then declined to 44% in 2017-2018. Of those adults with controlled blood pressure, the number taking blood pressure medication increased from 53% in 1999-2000 to 72% in 2013-2014, then declined to 65% in 2017-2018.