Planning a late night wrapping gifts and an early morning ripping them open? It may be wise to get more rest in the New Year, said researchers who found sleep deprivation may increase heart disease risk.

People who get five to seven hours of sleep nightly are almost twice as likely to develop early signs of blood-vessel damage as those who get more rest, according to a five-year study published in today's Journal of the American Medical Association. Those who regularly sleep less than five hours a night are at even higher risk.

Abnormal sleep patterns skew the release of appetite-related hormones, which may contribute to obesity and diabetes, earlier studies showed. Today's research is the first to suggest a shorter night's sleep may have a more direct and damaging effect on heart health, said Diane Lauderdale, the University of Chicago epidemiologist who led the research team.

"There's mounting evidence that really short sleep duration, as in less than five hours a night, may well have health consequences," she said Dec. 22 in a telephone interview. "It's pretty safe to say that it's a good idea to get more than five hours of sleep a night."

Heart disease, the leading cause of death worldwide, often occurs after years of damage to the blood vessels that surround and support the cardiac muscle. A key step in the damage occurs when deposits of calcium build up on blood-vessel walls, setting the stage for the growth of plaques laden with fat, clotted blood, and immune cells.

Calcium Buildup

Smoking, diabetes, high blood cholesterol and obesity have all been linked directly to calcium buildup in the coronary arteries around the heart. Lauderdale's group studied 495 people aged 35 to 47 who didn't have existing heart damage to see whether insufficient sleep might also contribute. The study participants were black and white men and women in the Chicago area.

People often report that they get more sleep than they actually do, so Lauderdale had them wear a wristband device, called an actigraph, that estimates sleep time by frequency of movement. In the study, while most subjects reported they were sleeping seven hours nightly, actigraphs showed the average length of sleep was closer to six hours.

The largest group of subjects got five to seven hours of sleep a night. In the five years of the study, about 11 percent of them developed calcified arteries. With less than five hours of nightly sleep, the danger rose starkly, with 27 percent of people developing blood-vessel calcification during the study.

Seven Hours

In contrast, only 6 percent of those who got more than seven hours a night showed signs of damage by the study's end. Lauderdale and other experts in the field were cautious about interpreting the results.

"Like most literature in the field, this study is observational, which means we can't be completely sure there's a cause-and-effect relationship between sleep and calcification," said Sanjay Patel, an associate professor and sleep expert at Case Western Reserve University in Cleveland who wasn't involved in the study. "It still suggests we should all make sure we're getting enough sleep."

Research indicates that average sleep hours in the general population have fallen in recent decades, perhaps as people work longer hours, spend time with their families, and get late-night entertainment from television and the Internet, Patel said.

"I suggest that people set aside seven hours for sleep each night, just as we might try to find an hour for the gym at least three days a week," he said. "That may mean that they can't watch the late show, or whatever."

The study was funded by the U.S. National Institutes of Health in Bethesda, Maryland. Further studies should be done to confirm the findings and determine whether people who sleep less have a higher rate of heart attacks or other forms of heart disease, Lauderdale said.