MONDAY, Nov. 21, 2005 (HealthDay News) -- Male infants born prematurely are at increased risk of developing high blood pressure decades later, Swedish researchers report.
The reasons for this rise in risk are unclear; however, the researchers don't think it can be explained by family history or genetics. Rather, they believe environmental challenges linked to prematurity may explain an increased risk for high blood pressure later in adulthood.
"Preterm-born men have an increased risk of high blood pressure and the risk is inversely proportional to the degree of prematurity -- the more premature, the higher the risk," noted lead author Dr. Stefan Johansson, a neonatologist at Karolinska University Hospital in Stockholm.
The study only included male babies -- experts note that a similar study in females might turn up similar trends.
The report appears in the November 29 edition of Circulation: Journal of the American Heart Association.
In their study, Johansson's team collected blood pressure and birth data on nearly 330,000 Swedish men born between 1973 and 1981.
They found that, compared with males born full-term, males who were born extremely preterm -- less than 29 weeks -- have almost twice the risk of developing high systolic blood pressure in adulthood. Systolic pressure refers to the first number in a blood pressure reading.
In addition, those who were very preterm -- 29 to 32 weeks -- had a 45 percent increased risk of high systolic blood pressure, while those born moderately pre-term -- 33 to 36 weeks -- had a 24 percent higher risk.
"The risk associated with preterm birth is most probably not explained by familial factors," Johansson said. "Our study further supports the concept that diseases in adulthood are associated with very early exposures [to environmental challenges]," he added.
Johansson thinks more research is needed on why preterm birth is associated with this risk of high blood pressure and recommends intervention as early as possible. "I think that clinical follow-up programs of children born more than three months before term should include blood pressure checks during their visits," he advised.
Another expert pointed out that these findings were confined to males only.
"At the present time, the study cannot be extrapolated to women born preterm because only men were included in this study," said Dr. Nieca Goldberg M.D., chief, Cardiac Rehabilitation and Prevention Center, Lenox Hill Hospital, and assistant clinical professor, medicine, New York University School of Medicine, in New York City.
"Other studies should be done to see if this relationship can be applied to women and people of various racial and ethnic backgrounds," she said. "Work like this will help us to identify risk factors earlier in life and apply preventive strategies that will ultimately reduce risk of heart disease and stroke."
Another expert said the study may shed more light on the causes of high blood pressure.
"This is a very interesting study," said Dr. Roger S. Blumenthal, an associate professor of medicine and director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease in Baltimore. "It shows that what happens to us when we are born can affect the development of high blood pressure 40 plus years later, which is quite fascinating. This may help to shed light on some of the other causes of high blood pressure."
Blumenthal adds that knowing this makes it even more important to make the lifestyle changes that help fight high blood pressure.
"People need to remember that the best way to prevent or control hypertension and type 2 diabetes is to exercise more and follow better dietary habits," he noted. "For now, that should be the focus of our efforts in America and elsewhere."
The American Heart Association has more on high blood pressure.