First, the bad news: More American adults have hypertension (high blood pressure) and prehypertension than ever before.

Now, the good news: The percentage of those getting treated for and controlling high blood pressure has also increased. As a result, even the bad news has a good news aspect: more people are living with rather than dying from hypertension.

The bad news/good news portrait of the disease — reported in Hypertension: Journal of the American Heart Association — emerged from an analysis of data from two national health studies. Researchers at the National Heart, Lung, and Blood Institute (NHLBI), of the National Institutes of Health, said the nation’s obesity epidemic is a major factor in the increased prevalence of hypertension.

"That confirms what others have observed based on more limited data and what one would expect, because obesity is an important cause of high blood pressure," said Jeffrey A. Cutler, M.D., lead author of the study and a consultant to NHLBI’s Divisions of Prevention and Population Sciences and Cardiovascular Diseases.

Researchers compared the hypertension findings of the third National Health and Nutrition Examination Survey (NHANES III), which ran from 1988–1994, with data from the first six years (1999–2004) of the current NHANES, which collects information continuously in two-year blocks. They examined data from 16,351 NHANES III respondents and 14,430 surveyed during 1999–2004, all age 18 or older.

The age-standardized prevalence rate for hypertension rose from 24.4 percent to 28.9 percent. Being overweight or obese accounted for part but not all of the increase in high blood pressure among different age and race/ethnicity groups.

Prevalence is an estimate of the total number of cases of a disease existing in a population during a specified period. Prevalence is often expressed as a percentage of the population.

"We see that much of the magnitude in men is accounted for by obesity, but less so in women, possibly because of some unexplored changes in risk factors for hypertension," said Paul D. Sorlie, Ph.D., co-author of the study and Epidemiology Branch Chief in the Division of Prevention and Population Sciences.

Among the key results of the analysis under prevalence:

• The age-specific prevalence increased in all age groups starting at age 40 in women and age 60 in men.
• The most notable change in most race and gender groups was an upward trend in blood pressure categories. This lowered the percent of Americans with normal pressure (from 55.5 percent to 50.3 percent). Prehypertension — defined as readings of 120 to less than 140 systolic and/or 80 to 89 diastolic — increased from 32.3 percent to 36.1 percent. (Systolic is the upper number—the pressure when the heart is beating, while diastolic, the lower number, is the pressure when the heart is relaxing.)

Among the key results of the analysis under awareness, treatment and control:

• During 1999–2004, 72 percent of Americans with hypertension were aware they had the disorder, 61 percent were undergoing treatment, and 35 percent had their blood pressure under control.
• Hypertension awareness increased more than 5 percent among men. It also increased among non-Hispanic black women.
• Treatment rates improved in all race-gender groups, with significant increases in non-Hispanic white men and non-Hispanic black men and women.
• Control rates also tended to improve across races and genders. Non-Hispanic white and black men had the largest increases, from 22 percent to 39 percent and from 17 percent to 30 percent, respectively.
• Significant control improvement was not shown in white women between the two studies. "Thetrend lines have reversed," Cutler said. "Hypertension among white men is now being controlled as well or better than among white women."
• Mexican-Americans continue to have lower control rates than other ethnic groups, especially among young men (16 percent) and older women (19 percent).

"Our success with hypertension treatment and control, while considerable, is far from ideal," Cutler said. "Most importantly, we have to do a better job of prevention."

The NHLBI and the National Center for Health Statistics funded the study.

For more information on the American Heart Association, visit www.americanheart.org.