NEW YORK (Reuters Health) - A lack of enough exercise may account for some--but not all--of the greater propensity for black Americans to develop high blood pressure compared with those from other ethnic backgrounds.

Overall, people who exercise moderately to vigorously at least five times a week are 25% less likely to have high blood pressure, or hypertension, than their peers who get no exercise, according to a report in the February issue of Preventive Medicine.

However, while black Americans seem to be more likely to be sedentary, with 32% of black respondents reporting no physical activity in a week compared with 18% of non-Hispanic white Americans, blacks who did report exercising still had a higher likelihood of developing hypertension than whites who exercised an equivalent amount, the report indicates.

This suggests there may be additional risk factors other than a lack of exercise for the high rates of high blood pressure among black Americans. For example, some researchers have suggested that black Americans could have a lessened ability to properly excrete salt, which can lead to hypertension, said study co-author Dr. David R. Bassett, Jr., a professor in the department of exercise science and sport management at the University of Tennessee at Knoxville.

"Even after we adjusted for different levels of physical activity, blacks had a greater level of hypertension," Bassett told Reuters Health. "So at any level of physical activity, blacks were more likely to have hypertension than whites."

In the study, Bassett and colleagues analyzed data taken from more than 12,000 Americans who participated in the third National Health and Nutrition Examination Survey.

Overall, 31% of non-Hispanic blacks, 21% of Mexican Americans and 21% of non-Hispanic whites had hypertension. Hypertension was defined as having a systolic blood pressure of 140 mm Hg or greater (the first number in a blood pressure reading), or a diastolic blood pressure of 90 mm Hg or greater (the second number in a reading), or taking hypertensive medications.

One limitation to the study is that because the study design did not allow the researchers to assess physical activity obtained on the job, they may have underestimated physical activity in black study participants, Bassett noted.

Still, combining this study with the findings of other research suggests that physical activity can lower the risk of hypertension across all ethnic groups.

"The take-home message is that regular physical activity does appear to be associated with a lower prevalence of hypertension," Bassett said. "Blacks would still be at higher risk (of hypertension) than whites who exercise the equivalent amount, but they would have a lower risk than blacks who are sedentary."

SOURCE: Preventive Medicine 2002;34:179-186.

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