The researchers measured the volunteers' pulse and blood pressure during the various tests. They reported their findings in the October issue of the Journal of Applied Physiology.
They found that blood pressure dropped during the typical 9.5 minutes of time between "lights out" and sleep by a small amount -- an average of 4.7 mmHg systolic and 3.6 mmHg diastolic.
"There is hardly any change in blood pressure during the nap period itself," Atkinson said, adding that those findings correlate with other research into nighttime sleep.
Atkinson cautioned, however, that the study didn't show that the minutes before sleep are actually good for the heart. Nor did the research consider the typical increase in blood pressure after nighttime sleep that has been linked to a higher rate of sudden heart attacks in the morning.
"The increase in blood pressure after waking from a daytime nap might be just as important as the pre-sleep reduction," Atkinson said. "We plan to study this in the future."
Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, who's familiar with the study findings, said, "Whether napping will offer additional benefits to what is tried and true is unknown.
"Individuals interested in lowering their cardiovascular risk should focus on maintaining healthy blood pressure, healthy lipid [cholesterol] levels and healthy weight, and exercise and don't smoke," he said.
To learn more about heart attacks, visit the American Heart Association.
SOURCES: Greg Atkinson, Ph.D., physiologist, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, England;
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