Of those who do, regularly seeing a doctor makes a big difference in their medication adherence.
In a study of California adults, of 42,044 respondents, 11,467 of them said a doctor had told them they had high blood pressure. When adjusted for age, this yielded a prevalence rate of 24.5 percent.
Researchers also found, on an age-adjusted basis, that 49.4 percent of those diagnosed with hypertension, a potentially life-threatening disease, were not taking drugs to lower it. People who had seen a physician during the prior year were more than five times more likely to be on medication than were those who had not.
"That was informative," said David J. Reynen, M.P.P.A., M.P.H., lead author of the study. "It really underscores the importance of having routine care."
High blood pressure is a major risk factor for heart attacks and strokes, and it increases a person's risk of heart failure, kidney disease and blindness.
Doctors recommend drug treatment when a person's blood pressure consistently measures 140/90 millimeters of mercury (mm Hg) or higher. Reynen and his colleagues at the California Department of Public Health's Heart Disease and Stroke Prevention Program in Sacramento wanted a clearer picture of high blood pressure in their state. They proposed a series of questions to be included in the California Health Interview Survey, which is conducted by telephone every two years, and then analyzed the results.
"Unfortunately, the data are collected in such a way that we don't know to what degree the individual respondents have hypertension," Reynen said. "One in four adults in California, including one in three African Americans, is hypertensive," he said. "We talk about people needing to know their numbers. That means not just whether your blood pressure is high or low, but your actual numbers. This study reinforces that."
The researchers used age-adjustment to standardize the survey results so they could more accurately compare various groups. Among those surveyed with high blood pressure, the analysis showed that the age-adjusted odds of a person taking drugs to lower blood pressure are:
* 5.23 times higher for people who saw a physician within the past year compared to those who did not;
* 2.47 times higher for those with diabetes than those without the disease;
* 2.05 times higher for those who had health insurance than those who did not;
* 1.71 times higher for African Americans than for whites (the racial/ethnic groups, respectively, with the highest and lowest high blood pressure rate);
* 1.46 times higher for people who described their health as poor or fair compared to those in good health;
* 1.40 times higher for patients diagnosed with heart disease than those without it;
* 1.38 times higher for smokers than nonsmokers;
* 1.27 times higher for U.S.-born individuals than foreign-born;
* 1.21 times higher for people with some form of formal education after graduating high school than those with less formal education.
"Understanding these factors may allow us to develop better strategies to increase the use of blood-pressure-lowering drugs among those with high blood pressure," Reynen said.
The age-adjusted prevalence of high blood pressure and drug treatment sometimes varied considerably among the various groups surveyed:
* African Americans had the highest prevalence of high blood pressure (35 percent), followed by American Indians (29.8 percent), Pacific Islanders (27.2 percent), those of other race/ethnicity (25.9 percent), Latinos (25.0 percent), Asians (24.5 percent) and whites (23.1 percent).
* African Americans had the highest rate of drug use to control their high blood pressure (56.6 percent), followed by American Indians (53.1 percent), Asians (52.1 percent), Pacific Islanders (52 percent), whites (49 percent), Latinos (45.8 percent) and those of other race/ethnicity (44.4 percent).
"Physicians should be mindful of these kinds of associated factors when developing treatment plans, and public health officials should be mindful of them when developing public health interventions," Reynen said. "Knowing someone's racial/ethnic group may be helpful to us when we try to target messages to this population to tell them they need to see a physician if they have high blood pressure."