June 15, 2010 -- Adolescent boys with normal blood pressure are three to four times more likely than girls to develop high blood pressure, a large study has found.
An international team of researchers analyzed data on 23,191 males and 3,789 females and followed them from age 17 to 42. The participants had periodic readings of blood pressure and body mass index (BMI), a measurement based on height and weight. During the long-term follow-up period, 14% of the group developed high blood pressure, which is a major risk factor for heart disease.
Other study findings:
- During a maximum of 17 years of follow-up, men were four times more likely than women to develop high blood pressure.
- For teenage boys in the upper range of a normal weight and with a systolic blood pressure (the top number in a blood pressure reading) of 110 or above, the risk of high blood pressure increased at 1% per year.
- For boys and girls, BMI at age 17 was strongly associated with future risk of high blood pressure, even after adjusting for blood pressure. However, for boys, the risk of developing high blood pressure held throughout the entire BMI range, including what is considered a normal weight range (BMI of 18 to 25), and the association between BMI and blood pressure was particularly strong for boys.
- For girls, only those who were considered clinically obese, meaning they had a BMI of 30 or higher, had a significantly increased risk of high blood pressure. The researchers said the sex hormone estrogen may protect against high blood pressure.
- Blood pressure values were higher among teenage boys than girls, despite a lower mean BMI. Blood pressure readings that fell within the low-normal range were two times more prevalent among girls than boys.
Blood Pressure and Adolescence
The findings are published in the latest issue of Hypertension: Journal of the American Heart Association. The participants were part of the Metabolic Lifestyle and Nutrition Assessment in Young Adults (MELANY) study, conducted at the Israel Defense Forces Staff Periodic Examination Center.
“Blood pressure values well below the hypertensive range already can serve as good predictors for future hypertension,” said study author Amir Tirosh, MD, PhD, a fellow in the department of medicine at Brigham and Women’s Hospital in Boston. “The rate of progression to hypertension is higher in teenagers whose systolic blood pressure is 110 versus those whose blood pressure is 100, and is different between boys and girls.”
Researchers are interested in looking at blood pressure levels in adolescents and even children because it is believed that heart disease may begin as early as childhood. Also, obesity is a major risk factor for heart disease and high blood pressure. In the United States, childhood obesity has more than tripled in the past 30 years. Researchers say pediatricians should pay more attention to blood pressure readings in children and adolescents so that they can better identify who may be at risk for high blood pressure in adulthood.
Tracking BMI and blood pressure through childhood and adolescence could “provide a simple and useful tool that can serve as a red flag to detect subgroups of teens at high risk of hypertension as adults while in their teens,” Tirosh said. “Hypertension, heart disease, and their prevention have been perceived as more relevant to an older population, but now we know that slight changes in blood pressure and weight should represent an alert for pediatricians to begin prevention as early as possible. It is better to prevent a disease than treat it.”