Vitami.n C lowers bloo.d pressur.e

Tuesday November 11, 2008 (foodconsumer.org) -- Sleeping for less than 7.5 hours a night may increase risk of heart disease and stroke and death in people with high blood pressure, according to a new study released Monday.

The study of more than 1,200 Japanese men and women with high blood pressure showed those who slept for less than 7.5 hours a night were more likely to suffer a heart attack or stroke or die of cardiac arrest over a period of 4 years compared to those who slept for a longer time.

Higher risk was particularly significant among short sleepers who could not lower their blood pressure overnight, which normally occurs, according to the report published in the Nov 10 2008 issue of the Archives of Internal Medicine.

The results of the study suggest that doctors need to ask their patients with high blood pressure about their sleep habits and advise them to have sufficient sleep to avoid cardiovascular events.

Dr. Kazuo Eguchi M.D., Ph.D. of Jichi Medical University in Tochigi, Japan, lead author of the study, said doctors should identify and monitor people who are both short sleepers and can't have their blood pressure decline overnight.

The 50-month study was based on data from 1,255 men and women aged 33 to 97 who had high blood pressure. They monitored each participant's blood pressure changes over a 24 hour period using portable blood pressure monitors.

During the study, 99 heart attacks, strokes or deaths from cardiac arrest were recorded.

Overall, men and women who slept for less than 7.5 hours a night were 68 percent more likely to have one of these cardiovascular events than those who slept for longer periods.

"The incidence of cardiovascular disease was 2.4 per 100 person-years in subjects with less than 7.5 hours of sleep and 1.8 per 100 person-years in subjects with longer sleep duration," the authors wrote.

Those who had shown no decline in their blood pressure overnight were at higher risk compared to those who had.

A much higher risk was found in those who both slept insufficiently and had an overnight increase in blood pressure compared to those with normal sleep duration plus no overnight increase in blood pressure. These people were four times more likely to have heart attack, stroke, or death from cardiac arrest.

Earlier chronic sleep deprivation has been already associated with higher risk of a number of health problems such as diabetes, coronary heart disease and obesity.

The researchers explained that insufficient sleep leads to increased nervous system activity, which could stress the cardiovascular system and no-dipping overnight blood pressure has been already linked to increased nervous system activity during the day.

They concluded "shorter duration of sleep is a predictor of incident cardiovascular disease in elderly individuals with hypertension," particularly in those with elevated nighttime blood pressure, the authors noted.

Sleep deprivation per se is likely to cause high blood pressure, previous studies suggest.

An October 2007 study of 10,300 adults in the medical journal Hypertension suggests that women age 35 to 55 who routinely sleep fewer than seven hours a night may have an increased risk of developing high blood pressure.  Women who routinely slept for less than five hours per night had a 31 percent higher risk compared to those who slept more than 7 hours a day.   Those who slept less than 6 hours per night were 42 percent more likely to have blood pressure.

Another study of 4,810 participants age 32 to 86 published in the May 2006 issue of hypertension suggests that long term sleep deprivation increases the risk of hypertension.   Researchers found among participants age 32 to 59, those who slept for less than six hours a night had more than double the risk of high blood pressure than did those who slept for more than six hours per night.

Hypertension is the medical term for high blood pressure, which by definition means blood level is 140/90 mmHg or higher.   In the United States, 73 million people age 20 and older have high blood pressure and the condition killed 54,707 people in the country according to the American Heart Association.