Physical activity may reduce risk of hypertension in African Americans

An analysis of a community-based study found that higher levels of moderate or vigorous physical activity (MPVA) or sport/exercise-related physical activity were associated with a lower risk of incident hypertension among African Americans.

However, after adjusting for potential confounders, total physical activity as well as occupational, household and lifestyle physical activities were not associated with incident hypertension.

Lead researcher Keith M. Diaz, PhD, of Columbia University Medical Center in New York, and colleagues published their results online in Hypertension on Jan. 30.

The researchers noted that 40.8 percent of African American men and 41.5 percent of African American women have hypertension. African Americans have the highest rates of hypertension among ethnic/racial groups and have a disproportionate number of premature disabilities and deaths from MI, stroke and end-stage renal disease.

“High blood pressure is a major health issue for many African Americans,” Diaz said in a news release. “Instead of waiting for full-blown hypertension or abnormally high blood pressure to develop in African Americans, health professionals should prescribe a dose of physical activity, just as they would prescribe a medication.”

For this analysis, the researchers evaluated participants from the Jackson Heart Study, which enrolled African American adults who resided in Jackson, Mississippi, between 2000 and 2004. They examined 1,311 participants who had a systolic blood pressure of less than 140 mm Hg and a diastolic blood pressure of less than 90 mm Hg, attended follow-up examinations and were not taking antihypertensive medications at baseline.

Participants completed a 30-item questionnaire on physical activity at baseline based on four domains: active living habits, work, home life and sport/exercise activities. They also had their blood pressure measured at each visit.

The researchers defined incident hypertension as systolic blood pressure of 140 mm Hg or higher, diastolic blood pressure of 90 mm Hg or higher or self-reported antihypertensive medication use. They also considered poor MPVA as zero hours of MPVA per week, intermediate MPVA as less than 150 hours of moderate physical activity per week and less than 75 hours of vigorous physical activity per week and ideal MPVA as at least 150 minutes of moderate physical activity per week and at least 75 minutes of vigorous physical activity per week.

Of the participants, 39.2 percent had poor MPVA, 37.1 percent had intermediate MPVA and 23.7 percent had ideal MPVA. Participants with higher levels of MPVA were more likely to be younger and male and less likely to have diabetes, less than a high school education and a family income below $50,000 per year.

During the follow-up period, there were 650 cases of incident hypertension, representing 49.6 percent of participants.

Participants in the intermediate group had a 16 percent lower risk of high blood pressure and participants in the ideal group had a 24 percent lower risk of high blood pressure compared with participants who did not exercise.

Sport or exercise-related physical activity lowered the risk of hypertension, while levels of physical activity from working or doing household chores did not change the risk of hypertension.

“We think that occupational or household activity is often not done in bouts long enough to cause healthy changes in your heart, blood vessels and muscles,” Diaz said in a news release. “Other research has shown that for physical activity to be beneficial, it needs to be done for at least 10 consecutive minutes at a time and at intensity levels that get you breathing harder and your heart beating faster.”

The researchers acknowledged a few limitations of the study, including that participants self-reported their physical activity. They also only assessed MPVA per week from the sport/exercise domain, so the MPVA could have been underestimated. In addition, the study only took place in one metropolitan area, so the results might not be generalizable to other African American populations. Further, they mentioned the study’s observational design meant it was subject to residual confounding from unmeasured factors.

“This landmark study provided a unique opportunity to characterize physical activity levels in four separate domains and evaluate their association with incident hypertension to elucidate the type of physical activity that mitigates risk for the development of hypertension in African Americans,” the researchers wrote. “The results of the current study provide evidence that increasing sport or exercise-related physical activity may reduce the incidence of hypertension among African Americans.”