Expectation produced small drops in blood pressure, but more study needed, researchers say
FRIDAY, Nov. 2 (HealthDay News) -- A nap a day may keep the heart doctor away -- at least that's what recent research suggests. Now, a new British study reports that the first few minutes before you doze off might be an especially restful time for your heart.
Blood pressure dropped during those minutes but not when the study participants simply rested or stood for an hour, according to the study. But a co-author of the study cautioned that the findings shouldn't be enough to send anybody off for a midday snooze.
"Any extrapolation of the study results to the benefits of napping is a bridge too far," said physiologist Greg Atkinson of the Research Institute for Sport and Exercise Sciences at Liverpool John Moores University in the United Kingdom.
Midday naps may boost heart health, at least according to a recent study in the Archives of Internal Medicine that was the first to consider the influence of other factors like diet and exercise on the heart. Researchers looked at health records of 23,681 people in Greece and found those who napped at least three times a week for a half hour or more had a 37 percent lower risk of dying from heart disease, compared with people who didn't nap.
While less extensive studies have not supported napping as good for the heart, people in Mediterranean and Latin American countries where siestas are popular do have lower rates of heart disease, the study authors noted.
For the new study, the researchers recruited nine healthy volunteers -- eight men and one woman -- who didn't routinely take afternoon naps. They went to a sleep laboratory on three afternoons after sleeping just four hours the night before.
At the lab, the volunteers did something different each afternoon. During one afternoon, they spent an hour resting, but not sleeping, in bed. On another afternoon, they had to stand for an hour. On the third afternoon, they napped for an hour.
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; Gregg C. Fonarow, M.D., professor, cardiology, University of California, Los Angeles; October 2007 Journal of Applied Physiology
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