First, it is important to note that snoring may just be the tip of the iceberg. Snoring can be a clue to a more-serious condition called obstructive sleep apnea that often includes snoring but also has blockage of breathing during sleep. About half of patients with snoring that regularly wakes up other people will have obstructive sleep apnea. Obstructive sleep apnea—especially severe obstructive sleep apnea—is associated with health problems like high blood pressure and increased risks of heart attack, stroke, or death. There is limited evidence about other health risks as well. Obstructive sleep apnea can cause disruption of sleep, leading to sleepiness and fatigue that have their own dangers, especially related to driving and even workplace accidents.
But what if someone snores but has a sleep study showing that they do not have obstructive sleep apnea? For snoring alone (snoring without obstructive sleep apnea), it is unclear if this may also be dangerous. Snoring alone has generally been considered a social nuisance, but there are some intriguing studies suggesting that there may be some health risks that need a closer look.
Someone’s Own Report of Snoring May Not Reflect Health Risks
Many studies have shown that snoring is associated with health problems, but most of these studies grouped people who snore with and without obstructive sleep apnea together. The result is that they were unable to show specifically whether snoring alone was associated with the health problems.
Similarly, studies that have examined snoring alone often relied on someone’s own report of whether they snored or not. For example, a landmark Spanish study showed that untreated severe obstructive sleep apnea was associated with a risk of heart attack, stroke, and death over a 10-year period ( https://www.ncbi.nlm.nih.gov/pubmed/15781100). This study also found no health risks for those with snoring alone, although this was based on self-reported snoring. As you can imagine, someone may not know whether they snore or how much they snore. However, it was generally accepted that snoring alone was not associated with health problems, and there had to be a reason to go through the trouble of recording someone’s snoring and examining whether measured snoring was an issue.
Challenging the Thinking on Snoring Alone and Health Risks
An Australian group was the first to question the idea that snoring alone was not associated with health problems. They performed some animal studies suggesting that the vibration of snoring alone may contribute to an increased risk of stroke. In one study of anesthetized rabbits ( https://www.ncbi.nlm.nih.gov/pubmed/21629363), the right carotid artery was exposed to 6 hours of vibration that was designed to be similar to the vibration from snoring. They carefully avoided changes seen in obstructive sleep apnea such as decreases in oxygen levels or irregular heart rhythms. The right carotid artery had changes to its lining (where atherosclerosis starts) that were not seen on the left side where there was no vibration.
They followed this with a human study (https://www.ncbi.nlm.nih.gov/pubmed/18788645) that examined 110 subjects who underwent sleep studies and recording of snoring sounds, with measurement of how often people were snoring. The study also included artery ultrasounds to evaluate for the presence or absence of atherosclerosis in the carotid (neck) and femoral (leg) arteries. Those with severe snoring (more than 50% of sleep time with snoring) had an increased odds of carotid artery—but not femoral artery—atherosclerosis when compared to those with mild snoring (0-25%). This intriguing finding showed a possible mechanism for the vibration of snoring (vibration in the neck but not the leg) to be a cause of atherosclerosis in major blood vessels! A 10% increase in the amount of sleep time with snoring was associated with a 40% increase in the odds of having carotid artery atherosclerosis. This association was still there even after correction for other risk factors for atherosclerosis like obesity, smoking, cholesterol levels, and high blood pressure. The interesting and surprising finding was that the percentage of time with snoring was more important for carotid atherosclerosis than the severity of sleep apnea.
What about the Ultimate Health Risk of Snoring: Death?
Sleep studies used in patient care generally do not specifically measure snoring sound characteristics. However, the SNAP home sleep study system (SNAP Diagnostics, Wheeling, IL) and some other do. The SNAP home sleep study records the sound of snoring and characterizes the snoring as coming from the soft palate (palatal) or from other sources (non-palatal) with a proprietary method of sound analysis. A creative study used data from 77,260 individuals who had undergone SNAP home sleep studies and compared them to death records from the United States Social Security Death Master File. The study found that mortality was greater in those with a greater proportion of non-palatal snoring, compared to palatal snoring ( https://www.ncbi.nlm.nih.gov/pubmed/21493281). Interestingly, there was no association between mortality and the severity of sleep apnea (measured by the apnea-hypopnea index). In a subgroup of almost 6000 patients without sleep apnea who were not obese, an increase in the amount of snoring was associated with a small but meaningful increase in mortality. The study was not perfect, as they did not have the necessary information to correct for whether or not someone went on to treat their snoring or sleep apnea and what other medical conditions they had.
The Bottom Line Is That We Do Not Know If Snoring Alone Is Dangerous
Snoring alone may be more than just a social nuisance, as there is some research suggesting that it may have important adverse health consequences. This comes from the few studies with actual measurement of snoring; the finding that the more someone snores, the greater the risks; and even animal studies outlining a potential explanation. Further research examining snoring alone should include detailed measurement of the snoring to determine what aspects of snoring (loudness, percentage of the night with snoring) are the most important.