Washington, June 23 (IANS): Mild elevations in blood pressure considered to be in the upper range of normal during early adulthood can lead to subclinical heart damage by middle age, says a study.

Hypertension (high blood pressure) is one that tops 140/90 but pressure just below that threshold begins to fuel heart damage among young people and can lead to changes in heart muscle function in as little as 25 years.

"Our results suggest that the heart muscle may be more sensitive to the effects of even subtle elevations in blood pressure than we thought," said principal researcher Joao Lima, a professor of medicine and radiology at Johns Hopkins University School of Medicine.

The latest clinical guidelines define hypertension as blood pressure above 140/90, but they call on patients to aim for a pressure below 150/90.

A single cut-off measurement does not apply to all ages and what constitutes 'normal' should probably change with age.

In healthy people, blood pressure tends to rise slightly as they grow old, so while 150/90 may be a reasonable target for a 60-year-old, it may be too high for a 28-year-old.

"A number of patients in our study had 'high-normal' BP in their 20s and 30s but by the time they were 45, they had the heart function of a 75-year-old even if they never met the clinical definition of hypertension," Lima said.

The study followed nearly 2,500 men and women between ages 18 to 30 tracking their health over 25 years and over the span of seven clinical visits.

Only a small fraction, about three percent, had blood pressures that met the definition of hypertension at the beginning of the study.

The results highlight an opportunity to intervene and halt damage, the team said.

"Our results show the importance of regular blood pressure checks that begin early in life."

The study appeared in the Journal of the American College of Cardiology.