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By Anne Harding

MONDAY, August 29, 2011 ( — Missing out on deep sleep can leave you feeling slow-witted and irritable in the morning, but the consequences don't necessarily end there. Over time, too little deep sleep may also take a toll on your heart by contributing to high blood pressure, a new study suggests.

Healthy young and middle-aged adults spend about 20% to 25% of their sleeping hours in the stages known as slow-wave sleep (so called because of the brain waves associated with it). This sleep phase is considered restorative and has been shown to be important for memory and mental performance.

The new study, which included 784 men over the age of 65, adds to the growing evidence that slow-wave sleep is also essential to our metabolism and heart health. Compared to men who spent at least 17% of their sleep time in the slow-wave phase, those who spent less than 4% in this restful state had 83% higher odds of developing high blood pressure () years later, the study found.

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