Wednesday October 15, 2008 (foodconsumer.org) -- A new study published in the Nov. 2008 issue of hypertension found that more Americans than ever live with high blood pressure and many of them do not know about their condition.

The study found the percentage of people with high blood pressure increased from 50.3 to 55.5 percent between 1994 and 2004 while the rate of hypertension increased from 32.3 to 36.1 percent.

Paul D. Sorlie, Ph.D and colleagues, authors of the study, from the U.S. National Heart, Lung, and Blood Institute attributed the ever-increasing number of Americans with high blood pressure to the obesity epidemic and suggested that more prevention effort needs to be invested in preventing obesity.

A reader from Maryland suggests that the increase may have something to do the new guidelines on high blood pressure and in reality it may not be much of an increase if there is any.

There is some explanation for the increase in the incidence of high blood pressure.   Obesity is one factor to blame.   But studies point to another possibility, that is, lack of sleep may serve as an important risk factor for both children and adults.

A new study suggests that lack of sleep or poor sleep quality can be one of the reasons that increase risk of high blood pressure at least in teens ages 13 to 16 years.

The study found healthy teens who slept less than 6.5 hours a night were 2.5 times more likely to have elevated blood pressure compared to their peers who slept longer.

The study titled Sleep Quality and Elevated Blood Pressure in Adolescents was published in the Aug. 19, 2008 issue of Circulation.

For the study, researchers followed 238 adolescents ages 13 to 16 years old enrolled in the Cleveland Children's Sleep and Health Study to determine the association between high blood pressure and sleep quality.

The researchers found those with poor sleep or low sleep efficiency had on average 4 mm Hg higher systolic blood pressure and were 3.5 times more likely to have pre-hypertension or hypertension than those who slept well.

Teens need at least 9 hours of sleep a night.   But they regularly sleep less due to a variety of reasons.   The study subjects slept on average 7.7 hours with 11 % sleeping 6.5 hours or less a night.

The findings do not mean that sleeping less per se resulted in high blood pressure because there is no way to know the association is a causal relation.   But the possibility cannot be excluded.

An alternative explanation is that factors that contribute to poor sleep including stress, and caffeine intake may affect blood pressure directly.

Lack of sleep also increases blood pressure in adults.

A middle-aged person who sleeps five or less hours a night may increase his risk of high blood pressure, according to a study published in the April 2006 issue of Hypertension, Journal of the American Heart Association.

"Sleep allows the heart to slow down and blood pressure to drop for a significant part of the day," said lead author James E. Gangwisch, PhD at Columbia University's Mailman School of Public Health said

"However, people who sleep for only short durations raise their average 24-hour blood pressure and heart rate. This may set up the cardiovascular system to operate at an elevated pressure."

Gangwisch and colleagues found people who slept five or fewer hours per night were more likely to be diagnosed with hypertension even after other risk factors such as obesity, diabetes, physical activity, salt and alcohol consumption smoking and depression were considered.

The Gangwisch's study followed 4,810 people ages 32 to 86 for eight to 10 years. Participants did not have high blood pressure at baseline and at the end of follow-up, 647 became hypertensive.

According to these researchers, lack of sleep can be a risk factor.

High blood pressure if left untreated can increase the risk for heart disease, stroke, congestive heart failure, and kidney disease later in life. The condition is believed to kill about 300,000 people in the United States each year.   

An estimated 30 percent of American adults suffer hypertension with the highest rate in African Americans and the lowest rate in Mexican Americans. And about 28 percent of people have pre-hypertension.

High blood pressure is known by some as a silent killer and at least one third of the patients actually are not aware of their having the condition, according to an official document from the Centers for Disease Control and Prevention.