WEDNESDAY, June 17 (HealthDay News) -- Genetics can combine with lifestyle and demographic factors to affect blood pressure among American Indians, according to a study published online June 16 in Circulation: Cardiovascular Genetics.

Nora Franceschini, M.D., of the University of North Carolina in Chapel Hill, and colleagues recruited more than 3,600 American Indians from 13 tribes in Arizona, North and South Dakota, and Oklahoma who had participated in the National Heart, Lung, and Blood Institute Strong Heart Family Study which began in 1998. The subjects were interviewed and information was collected on exercise, alcohol use, smoking and socioeconomic factors. Each subject's blood pressure was taken, and high blood pressure was defined as ≥140/90 mm Hg, or the use of blood pressure medication.

The mean resting blood pressures among subjects was 123/76 mm Hg. The investigators found a combined genetic-behavioral effect on diastolic blood pressure among subjects who had smoked compared to those who had never smoked. Similarly, alcohol use combined with genetics to affect diastolic and systolic blood pressure among subjects who were drinkers compared to those who had never been drinkers. A genetic-behavioral effect on diastolic blood pressure also was observed among individuals with less than high school education compared to those with 12 or more years of school.

"Our findings suggest that behavioral and socioeconomic factors can modify the genetic effects on blood pressure phenotypes. Accounting for context dependent factors may help us to better understand the complexities of the gene effects on blood pressure and other complex phenotypes with high levels of genetic heterogeneity," the authors conclude.

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