Is Snoring a DiZZZease?
Nighttime noises may serve as a wake-up call for future illness
Snoring is one of those problems obvious to everyone but the person with the problem. Most snorers are oblivious to the rasping, grating noises they make. After all, they’re asleep. The next morning, however, snorers can suffer. They may find themselves unpopular among housemates, even in their own families. Many heavy snorers become the butt of unkind jokes.
Snoring severe enough to cause sleeplessness can lead to daytime drowsiness. Few people, whether they snore themselves or simply live with a person who snores, recognize that snoring may have serious medical consequences as well.
Over the past 20 years, a growing number of studies has linked snoring to heart disease and stroke, says Robert W. Clark of the Regional Sleep Disorders Center at the Columbus (Ohio) Community Hospital. Just over half the studies looking for such a connection have found one.
Some researchers see snoring as a condition similar to high blood pressure. Physicians took hypertension less seriously before researchers doing long-term studies of large groups linked it to heart disease and learned that treating it could reduce heart-disease risk.
Recent results, including those from two new, large studies of snoring among women, have helped clarify the problem, Clark says. Researchers, however, still need to sort out the effects of different types of snoring as they work to determine whether snoring is a cause or consequence of serious illnesses.
“Snoring is a very malignant condition when it’s severe,” Clark says. The problem is becoming increasingly common, he worries, because people in the United States weigh more and sleep less than they used to—both flabbiness and fatigue aggravate the racket.
Subscribe to Science News
Get great science journalism, from the most trusted source, delivered to your doorstep.
Snoring is an indication that air isn’t flowing freely through the area back where the throat joins the nasal passages. There, the tongue and upper throat meet the soft palate and uvula, the fleshy structure that dangles from the back of the palate into the throat. People with narrowed or partially blocked airways must pull in air quickly, creating turbulence that makes the structures vibrate. Snores result.
The most worrisome form of snoring is known as obstructive sleep apnea. In people with this condition, loud snoring is frequently interrupted by episodes of stopped breathing. The severity of this disorder varies widely. In the extreme case, the snorer finds it so difficult to draw in air that the airway gets sucked closed or collapses, and for milliseconds to minutes, no air flows at all. Alternatively, the airway may close partially, in a condition called hypopnea, so the sleeper gets less than a full breath.
During as much as half their sleep time, patients with sleep-apnea may show below-normal concentrations of oxygen in their blood. This lack of oxygen causes a patient’s heart to pump harder to circulate blood faster, and over time, it can lead to irregular heartbeats or high blood pressure.
Snoring without blockages in breathing is a less severe problem. Compared with a quiet sleeper, the so-called simple snorer experiences upper-airway resistance and a reduced airflow but gets more air than a person experiencing sleep apnea or hypopnea does.
Some researchers argue that the connection between snoring and heart disease, hypertension, and stroke is driven by those snorers who have sleep apnea. Clark, however, says that even simple snorers are at increased risk of disease. “People who are snoring are struggling so hard to breathe that they are putting stress on their heart” even if they continue breathing, he says.
To resolve this issue, investigators doing large studies must separate simple snorers from the 40 percent of snorers who suffer from sleep apnea or hypopnea. This distinction requires that researchers measure breathing while people sleep—a more difficult and expensive task than asking people whether or not they snore.
The search for a link between snoring and medical problems is also complicated by factors, such as obesity and advancing age, that predispose people to both cardiovascular disease and snoring. This makes it hard for researchers to tease out the risks attributable to snoring alone.
Additionally, since heart disease and strokes can weaken muscles and damage nerves, they can actually trigger snoring. So, studies that link snoring, hypopnea, or sleep apnea with disease don’t necessarily prove that snoring causes the medical problems.
Regardless, Clark suggests, “snoring itself is a warning sign and should prompt people to seek help.”
Since so many people are noisy sleepers, the possibility that simple snoring might boost a person’s chances of developing cardiovascular disease—one of the leading causes of death in the United States—has encouraged researchers in their work.
A new study that followed 71,779 women for 8 years as part of the nationwide Nurses’ Health Study suggests, but doesn’t prove, that snoring might itself be a risk factor for disease.
In 1986, researchers asked the nurses—all women—whether they snored regularly, occasionally, or not at all. None of the women had cardiovascular disease at the beginning of the study. Compared with nurses who said they don’t snore, those who reported that they snored regularly were 33 percent more likely to develop heart disease during the study, says Meir J. Stampfer of the Harvard School of Public Health in Boston.
Nurses who admitted to occasional snoring were about 20 percent more likely to develop heart disease or stroke than were those who claimed not to snore, he and his colleagues report in the February Journal of the American College of Cardiology.
Compared with women who said they didn’t snore, self-identified regular snorers were more likely to smoke cigarettes, drink alcohol, and work night shifts. They were also slightly older, heavier, and less physically active and more often had diabetes or hypertension—all of which predispose people to cardiovascular disease. The association between snoring and disease persisted even when the researchers took all these other risk factors into account, Stampfer says.
Like most studies, Stampfer’s work couldn’t easily distinguish between snorers who suffered from sleep apnea and those who didn’t. “However, we observed a significant increase in risk of cardiovascular disease, albeit small, among occasional snorers, who were most likely to be simple snorers,” he says.
Another problem faces scientists exploring links between snoring and serious illnesses: What is it about snoring that could make people susceptible to cardiovascular disease? Many researchers have suggested that, like sleep apnea, snoring may trigger hypertension, which then leads to heart disease or stroke. However, some studies have found hypertension to be no more common in snorers than in other people.
Stampfer’s team looked for a link between snoring and hypertension. This time, the researchers followed 55,720 nurses—many of them the same women as in the previous study—who didn’t have hypertension when they were first asked about their snoring habits.
Women who said that they snored regularly were 55 percent more likely to develop hypertension over the next 8 years than were those who said they didn’t snore, Stampfer and his colleagues reported in the Oct. 15, 1999 American Journal of Epidemiology. Women who said they snored occasionally were 29 percent more likely to develop hypertension than were women who reported no snoring.
These large, long-term studies are important in proving that snoring is in fact a risk factor for hypertension and heart disease, says Regina P. Walker of the Loyola University Medical Center in Maywood, Ill. Because Stampfer’s work carefully accounted for the effects of body weight, it demonstrates that snoring has an independent link to such cardiovascular disease, she says.
However, Walker disagrees with Stampfer’s view that separating occasional snorers from regular snorers sorts patients with sleep apnea from those without it. That distinction requires careful testing in a sleep laboratory, she says. Sleep studies can also determine how the intensity of a person’s snoring varies throughout the night.
Although such studies will be required to resolve the debate over snoring, sleep apnea, and disease, the weight of current evidence suggests a problem for even light snorers, Walker asserts. “I think people who snore should be worried. While snoring is just a sound, it is a sign a person is working harder to breathe,” she says. “If people don’t correct their snoring, as they age and gain weight, they will develop sleep apnea.”
A Swedish team taking a different approach to snoring has linked it to preeclampsia, a type of high blood pressure some women develop during pregnancy. This complication is a leading cause of maternal death, but its underlying mechanisms remain unknown, says Karl A. Franklin of University Hospital in Umeå. Snoring during pregnancy may reflect pregnancy-related nasal congestion and subsequent difficulty breathing, which might lead to hypertension, he says.
He and his colleagues gave 502 women a questionnaire about their sleeping habits during a past pregnancy. Seven percent reported that during the first trimester, they started to snore or snored more frequently than they had before the pregnancy. Six percent said the same about the second trimester, and 24 percent, about the third trimester.
During the last week of pregnancy, 23 percent of the women reported snoring every night, Franklin’s team says in the January Chest. Only 4 percent had reported snoring before becoming pregnant.
The researchers then looked at the women’s medical records and found that 14 percent of the self-reported regular snorers developed high blood pressure during their pregnancy, compared with 6 percent of the women who said they didn’t snore at all. Ten percent of the snorers and 4 percent of nonsnorers had developed preeclampsia, which is also marked by excess protein in the urine and swelling of the face, hands, legs, or feet.
Reported snorers were slightly more likely to have babies with low birth weights than were women who said they didn’t snore, Franklin says. This relationship stood even after the researchers took into account a woman’s age, weight, and smoking habits. Just over 7 percent of the snorers had a baby that was small for its gestational age, compared with 2.6 percent of those who claimed they didn’t snore. “The increased frequency of infants born small for their gestational age . . . indicates that the consequences of increased upper-airway resistance during sleep may affect the fetus,” Franklin says.
The connection between snoring and the baby’s birthweight is intriguing enough to warrant further studies, says J. Catesby Ware of Eastern Virginia Medical School and Sentara Norfolk General Hospital, both in Norfolk, Va.
However, Franklin and his colleagues haven’t yet shown that the snoring triggers preeclampsia, and the study is too small to be conclusive, says Ware. “It may be that people who snored more had greater weight gain,” he cautions.
Studies such as the upcoming Sleep Heart Health Study sponsored by the National Institutes of Health in Bethesda, Md., are needed to help tease out the risks due to snoring versus sleep apnea and hypopnea, says Walker. This study will document breathing patterns during sleep, including signs of apnea or hypopnea. The researchers will then follow the volunteers over several years to record any hypertension, heart disease, or stroke that develops.
In the meantime, bed partners are the best people to ask about whether a person has a problem with snoring, Clark says. “Most people that can drive a bed partner out of the room have a medical problem,” he warns.
Anyone who has a history of snoring regularly, pauses in breathing at night, is sleepy during the day, or experiences a dry throat in the morning, night sweats, or morning headache should consult a physician, he says. This is especially important for snorers who are extremely overweight or have unexplained hypertension.
Though most researchers suspect that quieting the snoring will eliminate the medical problem, that prediction hasn’t been confirmed. Ware says, “The next step is to see what difference treatment makes.”
Snorers may be able to stop their noisemaking by losing weight, treating their allergies, getting enough sleep, and refraining from smoking or drinking alcohol before bedtime, Ware says. If these steps don’t help, a mouthpiece that holds a person’s jaw forward may stop the snoring. Surgery can correct upper-respiratory abnormalities that make it easy for a person’s airway to become blocked, and a breathing mask that pushes air through a person’s airway all night can prevent sleep apnea and hypopnea, he says.
“If [treatment] doesn’t help the snorers,” Ware says, “it will certainly help their bed partner.”