Do you ever feel extra groggy when you wake up? It’s probably because you were awakened during what’s called slow-wave sleep (SWS)—the phase of sleep that’s deep, restful and restorative. The trouble is: If you frequently miss out on SWS, besides being tired, you could also be at greater risk for high blood pressure—and that’s very bad.

Researchers from various universities (including Harvard Medical School in Boston) recently found the association in their study, which was published in the August 30, 2011 issue of Hypertension. Since I sometimes have trouble getting a full night’s sleep, this news worried me. I placed a call to Susan Redline, MD, MPH, the Peter C. Farrell Professor of sleep medicine at Harvard Medical School and one of the authors of the study.

The Quality Of Your Sleep Matters

In the study, researchers recorded the sleep patterns of 784 older men (with an average age of 75) by using a polysomnogram that analyzed their brain waves for one night at home. The majority of these men were considered prehypertensive, meaning that their blood pressure was in the highest range of what’s considered normal. After approximately three years, the researchers checked both the blood pressure and the sleep patterns of the men again. The researchers found that 41% of the study participants who spent less than 4% of their sleep time in SWS during the second reading developed high blood pressure—while only 26% of those who spent approximately 17% or more time in SWS developed high blood pressure. In other words, the guys who got more deep sleep appeared to be more protected from developing high blood pressure.

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While this study involved older men, Dr. Redline said that these findings are likely relevant to everyone. In fact, similar studies have linked poor sleep to higher blood pressure even in children.

Dr. Redline’s study is just one more example of how the body needs sleep—and good sleep, she told me. She explained that SWS is particularly important in the restorative process because this is the period when both blood pressure and heart rate naturally go down to their lowest levels. So when people don’t get enough SWS, their blood pressure may not dip as much as it should during the night, which can lead to higher levels throughout the day.

To Get A More Restful Sleep

So how can you spend more time in SWS? Researchers aren’t sure exactly how to elicit more of it, said Dr. Redline, though she hopes that future studies will answer that question.

Will getting deeper sleep help treat high blood pressure someday? “Maybe,” said Dr. Redline. “But right now there is no data to support that.” In the meantime, don’t take this snooze news for granted. Getting seven to eight hours of sleep a night is sure to do your body good!