A recharged feeling is not the only benefit of afternoon naps, according to a new study in the U.K. Apparently, looking forward to an afternoon nap may lower risk of heart attack, too.

The study, conducted by John Moores University in Liverpool, England, found that changes in blood pressure could be one of the reasons why afternoon naps are beneficial to cardiovascular function since blood pressure and heart rates decrease at night during sleep, and lower blood pressure reduces the strain on the heart and the risk of a fatal heart attack.

Researchers tested nine healthy volunteers, eight men and one woman, who took routine afternoon naps. All participants visited the university laboratory on three separate afternoons following four hours of sleep the night before. Blood pressure, heart rate, and forearm cutaneous vascular conductance, which determines the dilation of blood vessels, were all analyzed.

In the study, volunteers spent one afternoon session resting for one hour, lying face up in bed without sleeping; another session involved volunteers who were relaxed but standing; and the last session involved a volunteer who was allowed to sleep for an hour, lying face up.

The study focused on the cardiovascular activity during daytime sleep in healthy individuals with a comparison to sleeping versus other daytime activities like standing or lying down without going to sleep. A significant drop in blood pressure was found during the sleep trial, but not during the resting or standing tests. The drop in blood pressure also occurred once the lights were out and just before the volunteer fell asleep.

In an epidemiological study of 23,000 people in Greece, those who regularly took afternoon naps showed a 37 percent decrease in coronary mortality compared to those who never napped. The individuals who occasionally napped in the afternoon had a reduction of 12 percent.

The John Moores team will study blood pressure during the waking portion of afternoon naps to see if there is potential risk of coronary mortality, since blood pressure has also been known to rise when people wake up and more cardiac deaths occur in the morning.