People who snore loudly, have difficulty falling asleep, or often wake up feeling tired may have more to worry about than dozing off at work. A new study suggests they may also be at increased risk of developing heart disease and other health problems down the road.
In the study, researchers at the University of Pittsburgh asked more than 800 people between the ages of 45 and 74 about the quality of their sleep. Three years later, the people who reported snoring loudly were more than twice as likely as quiet sleepers to have metabolic syndrome -- a cluster of risk factors for heart disease, diabetes, and stroke that includes high blood pressure, high blood sugar, low "good" cholesterol, high triglycerides, and excess belly fat.
People who had trouble falling asleep or who woke up feeling unrefreshed at least three times per week were about 80 percent and 70 percent more likely than their peers, respectively, to develop three or more of those risk factors, the study found. (A person must have three of the five risk factors to be diagnosed with metabolic syndrome.)
Sleep problems are "a big deal," says Jordan Josephson, M.D., an ear, nose and throat specialist at Lenox Hill Hospital, in New York City. "They're bad for the heart, bad for diabetes, and they lead to heart attacks and stroke.... It's going to shorten your life." (Dr. Josephson was not involved in the new research.)
Overall, 14 percent of the study participants developed metabolic syndrome. African Americans were more susceptible than whites, as were sedentary people compared to those who were physically active.
The findings, which appear in the journal Sleep, echo previous studies that have shown a link between sleep difficulties and health problems such as obesity and high blood pressure. But this is the first study to follow people with sleep problems over time to see if they develop metabolic syndrome, according to the authors.
Virend Somers, M.D., a professor of medicine at the Mayo Clinic, in Rochester, Minn., says that sleep deprivation is an epidemic that is almost in parallel with the obesity epidemic and the widespread rise of risk factors for heart disease and diabetes. The links between obesity and metabolic syndrome are well known, but the role that sleep plays has been less clear, Dr. Somers says.
The new study can't prove that snoring or any other sleep problem actually causes metabolic syndrome, which affects roughly 25 percent of the adults in the U.S. And although the researchers did control for race, physical activity, alcohol consumption, and other factors, it's possible that obesity is partly responsible for the link between sleep problems and metabolic syndrome.
However, sleep problems could directly contribute to risk factors for heart disease and diabetes. "Chronic sleep disturbances may produce high levels of stress hormones and have exaggerated cardiovascular responses, which could lead to changes in blood pressure, glucose metabolism, and weight," says the lead author of the study, Wendy Troxel, Ph.D., an assistant professor of psychiatry and psychology at the University of Pittsburgh.
The physics of snoring itself could even be to blame, Troxel says. Experiments have suggested that the body vibrations caused by snoring can increase potentially damaging inflammation in the linings of arteries, she explains.
Hormoz Ashtyani, M.D., medical director of the Institute for Sleep-Wake Disorders at Hackensack University Medical Center, in New Jersey, says that doctors should begin asking patients about their sleep quality in order to gauge their risk for heart disease and diabetes.
"If you see a new patient, you always ask them if [they] smoke, do [they] have heart disease, and so on," Dr. Ashtyani says. "Snoring and poor sleep should also be raised."