Small genetic differences may be the root of high blood pressure (search) risk in African-Americans, new research shows.

While blacks have long been known to have higher tendency toward high blood pressure, getting to the crux of the problem has been difficult. It’s not been clear which factors played the major roles — diet, exercise, income level, genetics, or a combination of factors.

In recent years, researchers have identified a set of 269 genetic markers or sequences that are shared by people of African and European ancestry. Most African-Americans have a racially mixed background, say the researchers, with some European ancestry. That was the foundation of this groundbreaking study, explains study researcher Neil Risch, PhD, a geneticist at Loyola University Medical Center in Chicago.

His report appears in the Jan. 23 online issue of Nature Genetics.

This study is the largest of its kind looking at this issue, Risch says. Researchers used genetic analysis from a set of unrelated Nigerian individuals to represent African ancestral population and they used the European Americans in the family blood pressure program to provide genetics of European ancestry.

The study also looked at genetics from African-American families. All the volunteers already had high blood pressure.

Through sophisticated genetic analysis, researchers identified two “signposts” for high blood pressure on a stretch of DNA (search) – on chromosomes 6 and 21 — among people of African descent, reports Risch. The signposts are not true gene variations, he explains. They simply help researchers identify which ethnic strand they are looking at.

Not that this finding solves the mystery entirely, Risch adds. “These regions [of DNA] have hundreds of genes, so it will take some time to whittle it down,” he says, in a news release.

The study is exciting from another perspective, he notes. This type of analysis shows great promise for understanding the intertwined risk factors — such as exercise, diet, and genetics — and their affect on chronic disease, says Risch.

The researchers conclude that the results indicate that these chromosomes may contain genes that influence the risk of high blood pressure in African-Americans.

The big questions remain: How might one gene increase blood pressure risk? Does it simply increase the problems caused by a bad lifestyle? Or does the gene alone cause high blood pressure — even in someone who does everything right? Nevertheless, it’s a first step toward understanding African-Americans’ high blood pressure risk, Risch says.

Risch’s finding could lead to new drugs or treatments to keep blood pressure under control. It could also help identify people at higher risk of heart disease.

By Jeanie Lerche Davis, reviewed by Brunilda Nazario, MD

SOURCES: Zhu, Xiaofeng, Nature Genetics, Advance Online Publication, Jan. 23, 2005. New release, Stanford University School of Medicine.