Preterm Birth Tied to High Blood Pressure in Men

NEW YORK (Reuters Health) - Blood pressure in young men is higher in those who were born prematurely, according to a report in Circulation: Journal of the American Heart Association. Further studies are needed to determine if this holds true for women as well.

"We hypothesized that preterm birth would be associated with high blood pressure later in life, but we did not expect the risk to be as high as it was," lead author Dr. Stefan Johansson, from the Karolinska Institute in Stockholm, told Reuters Health.

"It is well known that low birth weight in (full-term) babies is associated with high blood pressure, and we thought that preterm birth would provide a similar degree of risk. But, we found that preterm birth provides a higher risk than just being small at (birth)," he noted.

The findings stem from a study of 329,495 Swedish men who were born between 1973 and 1981 and had blood pressure measurements recorded 20 years later upon conscription for military service. Full-term, moderately preterm, very preterm, and extremely preterm births were defined as a gestational age of 37 to 41, 33 to 36, 29 to 32, and 24 to 28 weeks, respectively.

The risk of high systolic blood pressure (the top reading) increased steadily from 25 percent for moderately preterm birth to 93 percent for extremely preterm, compared with full-term birth. Being small for the length of pregnancy, also referred to as "gestational age," was only a risk factor for high blood pressure among subjects with a gestational age of at least 33 weeks.

Decreasing gestational age was also linked to increasing risks of high diastolic blood pressure (the lower reading), but the association was statistically significant only for subjects born moderately preterm.

The reasons for the link between gestational age and blood pressure are unclear, but "could involve structural changes in the vascular tree," Johansson said. Alterations in hormones could also play a role.

"One of the messages from this study is that children born preterm should have their blood pressure checked at follow-up visits, at least when they reach school age, because it may be important to consider other risk factors for cardiovascular disease as they are growing," Johansson said.

SOURCE: Circulation, November 21, 2005.