TUESDAY, Dec. 23, 2008 (HealthDay News) -- A good night's sleep may be just what your arteries need.
So finds a new five-year study in which middle-aged people who had an extra hour of sleep each night were less likely to have artery-stiffening calcium deposits.
But the study results shouldn't send people off to bed prematurely or have them popping sleeping pills, cautioned Diane Lauderdale, associate professor of health studies at the University of Chicago Medical Center, who led the study.
"We don't know why there is an association," Lauderdale said. "And until we know why, we can't tell whether it is a causal association."
The report was published in the Dec. 24/31 issue of the Journal of the American Medical Association.
Lauderdale and her colleagues have been following a group of young adults for years, studying their heart arteries from a number of angles. The latest report linked the sleeping habits of 495 participants, ages 35 to 47, with the incidence of artery calcification, measured by CT scans.
Calcium deposits can make the coronary arteries less flexible and ultimately lead to heart disease. None of the participants had detectable calcium deposits when the study began, but five years later, 61 (12.3 percent) did.
After adjusting for lots of potential risk factors, such as sex, race, and smoking habits, the researchers found that one more hour of sleep a night decreased the risk of calcification by a third. That's about as much as a 16.5-point reduction in blood pressure, the researchers said.
"Nothing came out of the study as appearing to explain the association," Lauderdale said. But she believes that there are three possible explanations.
One is that another factor, such as socioeconomic status, was the connection here. A second is that a stress-related hormone, cortisol, which has been tied to decreased sleep and increased calcification, is the link.
"Finally, sleep is related to blood pressure, and that is a coronary artery disease risk factor," Lauderdale said. "It's possible that for people who were sleeping more, their 24-hour blood pressure was lower than their daytime blood pressure."
Whatever the link, it was to be expected, said Kathy P. Parker, a sleep expert who is dean of the University of Rochester School of Nursing.
"We know that sleep deprivation does alter the physiology of numerous body systems, so it is not surprising that another health problem, or symptom or sign, should be related to sleep length," Parker said.
There is no precise formula for the length of sleep that is best for a given individual, Parker said. "There is considerable variation in sleep needs," she said. "On average, an individual needs between 7 and 8 hours of sleep. There is an increase in health problems with five hours or less or nine hours or more."
The best advice, said Parker, who is one of only five U.S. nurses certified by the American Board of Sleep Medicine, is "go to bed at a regular time, wake up at a regular time, pay attention to whether you feel refreshed and alert during the day, [and] avoid too much caffeine and alcohol."
As for sleeping pills, they are "appropriate in certain situations," such as times of acute psychological stress or jet lag or for "certain sleep disorders," Parker said.
"It's really important to wait until this finding is confirmed in another study population," Lauderdale cautioned. "Also, until we know the mechanism, it is premature to base clinical advice on this information."
More information
There's more on getting healthy sleep at the U.S. National Heart, Lung, and Blood Institute.
