Smoking, drinking, lack of exercise interact with genes to increase risk of hypertension

Dr. Nora Franceschini

“The three lifestyle characteristics are well-known risk factors for high blood pressure,” said Nora Franceschini, MD, lead author of the study and assistant professor of epidemiology at the UNC Gillings School of Global Public Health. “What’s new is that we are showing that these behaviors interact with your genes to influence blood pressure levels.

“The most interesting study finding is that a susceptibility to hypertension in your genetic background doesn’t mean that your lifestyle exposures do not matter; they do. Drinking, smoking and exercise habits can be modified, which would, in turn, influence the risk of developing hypertension, even in people who are predisposed to the condition.”

The researchers used family genetic and medical data gathered in the ongoing Strong Heart Family Study, a large epidemiologic study of American Indians. They analyzed data on 3,665 participants, ages 14 to 93, from large, multigenerational families residing in Arizona, North and South Dakota, and Oklahoma to see how inherited genetic patterns vary among those with different lifestyles and educational levels.

Among the statistically significant findings:

• Clear evidence of cigarette use and gene interaction (comparing smokers to never smokers) on diastolic blood pressure;
• Evidence that blood pressure among drinkers is affected by different genes than in former and never drinkers; and
• Evidence that an individual’s physical activity level influences the genetic effects on blood pressure.

The study examined the average effect of multiple genes tied to hypertension risk, and it demonstrated that behaviors can influence the effects of genes on blood pressure. Among the American Indians studied, approximately 15 percent of the variation in diastolic blood pressure (the force of blood in the arteries when the heart is at rest between beats) was due to genes, Franceschini said.

“So your level of blood pressure is influenced by your genes, whether you are a smoker or not, are physically active or not, or drink alcohol or not,” she said. “But those habits can still influence a person’s susceptibility to the disease.”

Study participants were an average 40 years old; 60 percent were female. Fifty-seven percent had smoked at some time, and 37 percent had less than a high school education.

Using pedometers, researchers measured physical activity over seven days in a subset of 3,110 participants. The group averaged 5,092 steps per day.

In the study, conducted among 13 American Indian tribes, researchers also observed a genetic interaction between greater education and a higher blood pressure levels. However, education itself does not explain the greater genetic risk, Franceschini said.

The researchers plan next to identify the particular genes that interact with each of the three behaviors to increase blood pressure. This will require genetic information from thousands of people, Franceschini said. The team expects to combine its data with that of researchers exploring the genetic basis for cardiac health in other racial/ethnic groups.

Kari E. North, PhD, associate professor of epidemiology, and Kathryn Rose, PhD, research associate professor of epidemiology, both at the UNC Gillings School of Global Public Health, co-authored the paper along with a dozen researchers from other institutions.

The study was funded by grants from the National Heart, Lung, and Blood Institute and the National Institutes of Health. Franceschini is supported by a grant from the American Heart Association.

UNC Gillings School of Global Public Health contact: Ramona DuBose, director of communications, or ramona_dubose@unc.edu.