The five-year study of more than 1,200 students in Montreal found that the risk of higher systolic blood pressure increased 19 percent a year for boys, but remained stable for girls. Systolic blood pressure, the larger of the two numbers in a blood pressure reading, represents pressure when the heart is fully contracted.

The researchers began tracking the students when they were in Grade 7.

This is the first study to document gender differences in blood pressure in adolescents and could help in the development of new strategies to reduce rates of hypertension in young male adults, the researchers said.

The findings are published in the current issue of the journal Circulation.

"It is important to document that, as the boys got older, they were more likely to have higher systolic blood pressure readings. It suggests that, as young adults, they may be more likely to develop hypertension," study lead author Dr. Kaberi Dasgupta, a physician at McGill University Health Centre and assistant professor of medicine at McGill University, said in a prepared statement.

He and his colleagues also found that a sedentary lifestyle and lack of exercise increased the risk of higher SBP in both boys and girls.

"Even after adjusting for differences in body weight, the more frequently a child engaged in active behavior, the lower the likelihood of developing higher systolic blood pressure levels," Dasgupta said.

"Perhaps more interesting, the more hours that the kids spent in sedentary behaviors -- sitting at a computer, playing video games, being on the Internet, watching television -- the more risk of having higher systolic blood pressure," Dasgupta said.