SEPTEMBER 2009

If you’re concerned about high blood pressure, make sure you get a good night’s sleep. A new study, among the first of its kind to objectively measure sleep duration, reports that for every one-hour reduction in sleep, the risk of hypertension increased 37%. Shorter sleep times were similarly linked with higher blood pressure levels and adverse changes in blood pressure.

Previous studies have suggested that not getting enough sleep may be bad for your blood pressure, but these mostly relied on self-reported data. The new study, led by Kristen L. Knutson, PhD, of the University of Chicago, monitored participants using actigraphy, in which a device on the wrist measures motion; since movement is reduced during sleep compared with wakefulness, the activity level indicates sleep duration. Sleep was measured twice for three consecutive days each time.

Knutson and colleagues followed a subset of 535 participants, average age 40 at baseline, in an ongoing study of coronary disease. Given that most people need seven to eight hours of sleep nightly, the study group fell far short of adequate shuteye: 43% averaged fewer than six hours of sleep per night, while only 1% averaged eight or more hours.

Over five years of follow-up, shorter sleep duration was significantly associated with increased risk of hypertension. Less sleep was also linked to adverse changes in both systolic and diastolic blood-pressure readings.

Even after adjusting for factors such as snoring, the connection between sleep duration and hypertension risk remained strong. “Poor quality sleepers had higher blood pressure risks regardless of whether or not they snored,” according to Knutson. Women who snored, however, were even more at risk of high blood pressure, though it’s unclear why. Knutson suggested that since snoring is less common in women, it may be more strongly associated with sleep apnea, a known risk factor for hypertension.

Besides snoring more, men in the study got less sleep than white women, who were at lowest risk of hypertension; African-American men were especially sleep-deprived. Writing in Archives of Internal Medicine, Knutson and colleagues noted, “These two observations suggested the intriguing possibility that the well-documented higher blood pressure in African- Americans and men might be partly related to sleep duration.”

Deaths attributable to hypertension among African-Americans are almost twice as common as among whites. Overall, about one-third of Americans suffer from high blood pressure, though many aren’t aware of their condition.

“Because of the major adverse health consequences of high blood pressure, the identification of a new and potentially modifiable risk factor has clinical implications,” Knutson and colleagues concluded. “Intervention studies are needed to determine whether optimizing sleep duration and quality can reduce the risk of increased blood pressure.”

TO LEARN MORE: Archives of Internal Medicine, June 8, 2009; abstract at archinte.ama-assn.org/cgi/content/abstract/169/11/1055. American Heart Association www.americanheart.org/presenter.jhtml?identifier=2114. National Heart, Lung and Blood Institute www.nhlbi.nih.gov/ health/public/heart/index.htm#hbp.