Teenagers who don't get enough shut-eye may not only be drowsy in class, but they could also be increasing their risk for high blood pressure and heart disease later in life, researchers say.

Teens who slept fewer than 6½ hours a night had more than twice the risk of high blood pressure, pediatrician Dr. Susan Redline of Case Western Reserve University in Cleveland, Ohio, and her team found.

'Part of the problem is the technological invasion of the bedroom with computers, cellphones and music.'— Pediatrician Dr. Susan Redline

A quarter of adults, about five million Canadians, have hypertension, a major risk factor for stroke and heart attack. Hypertension also contributes to kidney failure and dementia, according to the World Health Organization.

Similar studies linking poor sleep to heart disease have been done on adults, but this was the first to explore it in such a large number of young people.

Adolescents need nine hours of sleep, the researchers said. But sleep diaries showed that on average, teens got just 7.7 hours a night.

"Part of the problem is the technological invasion of the bedroom with computers, cellphones and music," Redline said.

"There are teens who text message or listen to music all night, compounded by early school hours. Parents should optimize sleep quality for their family with regular sleep and wake times and bedrooms should be kept quiet, dark and conducive to sleep."

Consider sleep issues, pediatricians advised

In the study, researchers measured blood pressure levels in a sample of 238 teenagers aged 13 to 16, both at home and at a sleep lab.

Those who had low sleep efficiency — such as being unable to fall asleep right away or waking up too early — were 3.5 times more likely to have high blood pressure than teens who did not have those problems, the team reported in Monday's online issue of the journal Circulation.

For adults, high blood pressure is defined as a reading of 140/90 or above. In children it is defined as being in the 90th percentile for their age.

About 14 per cent of teens studied had high blood pressure or were at high risk of developing it, the researchers found. Low sleep efficiency was found in 26 per cent of participants, and 11 per cent of the teens got less than 6½ hours of sleep.

After taking height, age and gender into account, they researchers also found an increased prevalence of low sleep efficiency among poorer children and minorities.

Childhood hypertension is associated with the condition in adulthood.

While the study cannot show if sleep issues are a symptom or cause of blood pressure, Redline suggested that pediatricians view sleep quality as an "intervenable health concern" alongside weight management and exercise.