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WESTMEAD, Australia, Sept. 4 -- Patients who snore heavily face a risk of carotid atherosclerosis 10 times greater than those with mild snoring, investigators here found.

The prevalence of carotid atherosclerosis increased in a linear fashion with severity of snoring, Sharon Lee, of the Ludwig Engel Center for Respiratory Research, and colleagues reported in the September issue of Sleep.

Snoring had no effect on the prevalence of femoral atherosclerosis.

"Heavy snoring significantly increases the risk of carotid atherosclerosis, and the increase is independent of other risk factors," the authors concluded. "Considering the high prevalence of snoring in the community, these findings have substantial public health implications for the management of carotid atherosclerosis and the prevention of stroke."

As many as half of middle-age adults snore habitually during sleep. Epidemiologic data suggest that self-reported habitual snoring and obstructive sleep apnea hypopnea syndrome are associated with cerebrovascular disease, although most sleep specialists consider the association between snoring and vascular disease a marker for obstructive sleep apnea, the authors said.

Research involving preclinical models has shown that the vibrations caused by snoring extend to the carotid artery wall and carotid lumen. Exposure to vibratory stimuli can damage endothelial cells, potentially triggering an inflammatory cascade that leads to atherosclerosis, the authors continued.

"Consequently, it is plausible that exposure to chronic snoring vibrations may cause carotid artery endothelial damage, thus contributing the pathogenesis of carotid artery atherosclerosis," they said.

In the current study the authors sought to determine whether snoring per se is a risk factor for carotid atherosclerosis. They recruited 110 adults, including self-reported snorers and nonsnorers. All participants underwent polysomnography, bilateral carotid and femoral artery ultrasound, and cardiovascular risk assessment.

On the basis of polysomnographic results, investigators grouped the volunteers by snoring as a proportion of sleep time: mild (0% to 25%), moderate (25% to 50%), and heavy (more than 50%).

Comparison of snoring status with carotid ultrasound findings showed that mild snorers had a 20% prevalence of carotid atherosclerosis, increasing to 32% in moderate snorers, and 64% in heavy snorers (P<0.04 for trend).

No association was seen between snoring and femoral atherosclerosis.

After adjustment for age, sex, smoking history, and hypertension, heavy snoring was associated with an odds ratio of 10.5 for carotid atherosclerosis (95% CI 2.1 to 51.8, P=0.004).

The odds ratio for heavy snoring was "much higher than for any of the traditionally accepted risk factors for atherosclerosis. Moreover, when the [apnea-hypopnea index], [arousal index], and measures of nocturnal hypoxemia were tested in any model, none showed significant associations with carotid atherosclerosis," the researchers said.

Collectively, the data showed that "objectively measured heavy snoring is a significant risk factor for the presence of carotid atherosclerosis," independent of other known risk factors, including the severity of obstructive sleep apnea.

The study was supported by the National Health and Medical Research Council of Australia and the Department of Veterans' Affairs of the Commonwealth of Australia. Coauthor John Wheatley, Ph.D., disclosed research funding from Boehringer Ingelheim, Astra-Zeneca, Cephalon, Takeda, and sanofi-aventis.

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