Hypertension and prehypertension in adolescents and young adults was associated with a higher risk of having an abnormally enlarged heart, researchers report in Circulation: Journal of the American Heart Association.

In a study of American Indians, average age 26.5, those with hypertension or prehypertension were more likely to have changes in the heart structure associated with increased cardiovascular risk: higher left ventricular wall thickness, higher left ventricular mass and higher prevalence of left ventricular hypertrophy. The prevalence of left ventricular hypertrophy was three times higher among those with hypertension and two times higher among those with prehypertension, compared to those with normal blood pressure.

Left ventricular hypertrophy is an abnormal thickening of the muscles of the heart's left ventricle (main pumping chamber). It is associated with heart and blood vessel complications, such as heart failure.

"The findings are a wake-up call for increased preventive measures to head off heart disease with lifestyle modifications, such as reducing caloric intake and increasing physical activity in this population," said Richard B. Devereux, M.D., senior study author and professor of medicine at Weill Medical College of Cornell University in New York City.

"At these younger ages, the increasing prevalence of early-onset hypertension and prehypertension is associated with changes in the heart that are related to worsened prognosis for heart disease, disability and death," he said.

Prehypertension is defined as systolic blood pressure higher than 120 mmHg but lower than 140 mmHg, or a diastolic pressure greater than 80 mmHg but lower than 90 mmHg, or both. Hypertension is defined as a systolic blood pressure greater than 140 mmHg or a diastolic blood pressure greater than 90 mmHg. Prehypertension is a relatively new category of blood pressure established by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-7). Devereux said this is the first large population-based study to examine the heart changes associated with the new JNC-7 category of hypertension.

"Previous research has found little difference comparing middle-aged to elderly overweight hypertensive white, black and American-Indian adults, suggesting that Indian populations are not unique, and may provide a preview of what other populations may experience as overweight and obesity rates increase," he said.

Researchers analyzed the association of prehypertension and early-onset hypertension with clinical characteristics and changes in heart structure and function in 1,944 participants (57.5 percent women) of the Strong Heart Study, an ongoing study of cardiovascular risk factors and disease in 13 American-Indian communities. In data collected from health examinations conducted between July 2001 and September 2003, researchers found early-onset hypertension in 294 participants (15 percent) and prehypertension in 675 participants (35 percent).

Both hypertensive and prehypertensive participants were more likely to be men, obese, have diabetes, and have impaired fasting glucose. Hypertensive and prehypertensive participants had higher average pulse pressure (the difference between systolic and diastolic blood pressure values), stroke volume index (related to the volume of blood the heart pumps out at each beat), and total peripheral resistance index (a reflection of how constricted peripheral blood vessels are – peripheral constriction causes blood pressure to rise). There was an early prevalence of increased arterial stiffness with multiple features related to insulin resistance.

"The frequency of heart abnormalities in these younger participants is similar to that found in the middle-age or adult population of hypertensives who are at risk for adverse events," Devereux said.

Jennifer S. Drukteinis, M.D., lead author of the study and an internal medicine resident at Weill Medical College of Cornell University, said the implications are clear: "There needs to be vigilant monitoring of blood pressure at younger and younger ages. Obesity and high blood pressure go hand-in-hand, and lifestyle modification is the key."