Snoring impedes blood flow in brain.

Surveys have linked snoring to strokes, but they have not revealed the basis for the connection. Now, researchers report that the obstruction of air passages that makes a person snore heavily or snort while sleeping can sharply reduce blood flow to the brain, possibly boosting the risk of stroke. Episodes in which air inflow is obstructed by more than 50 percent coincided with blood flow reductions of more than 50 percent in three-fourths of snoring episodes monitored, researchers report in the January Stroke.

To study the effects of snoring on blood flow, Kingman P. Strohl of Case Western Reserve University in Cleveland and his colleagues fitted 11 men and 1 woman with head gear that recorded their snoring patterns and the blood flow in their middle cerebral artery. The researchers found that obstructive apnea, in which a sleeper snores with abrupt snorts and pauses, and obstructive hypopnea, which causes heavy, long, loud snoring, decreased blood flow to the brain in 80 percent and 76 percent of incidents, respectively.

Both snoring conditions arise from upper airway obstructions that prevent the lungs from filling properly. This can create pressure inside the chest and on the heart, impeding blood outflow, says pulmonologist Strohl. The longer the snore, the greater the reduction of blood flow, his team found. Strohl likened the feeling to trying to breathe with a hand over one's mouth and nose. "It's this effort that causes lack of blood flow," he says.

While the reduced blood flow and later upsurge of blood to the brain after the obstruction clears seem to identify a risk pattern for strokes, no cause and effect has been proved, Strohl says. Surgery and other treatments can cure some snoring, but Stroh] cautions that research with more snorers is needed to link snoring and stroke definitively.