As if getting shingles isn't painful enough, researchers reported on Thursday that adults who get the rash have a 30 percent greater risk of developing a stroke than other adults.

They said the risk was even higher when the rash was clustered around the eyes, Dr. Jiunn-Horng Kang of Taipei Medical University Hospital reported in the journal Stroke.

Shingles, sometimes called herpes zoster, is an extremely painful recurrence of the chicken pox virus, which can lurk in the body for a lifetime. The infection usually starts with a rash on the face or body, and causes pain, itching or tingling.

Many studies have shown that people with herpes zoster infection are more likely to develop stroke. But ours is the first to demonstrate the actual risk of stroke following herpes zoster infection, Kang said in a statement.

He and colleagues studied 7,760 patients over 18 who were treated for shingles between 1997 and 2001. The average age of those studied was 47. They compared these to a group of people of similar ages who did not have shingles.

What they found is that people who had shingles were 31 percent more likely to develop a stroke than people who had not had shingles.

People whose shingles occurred on the skin in or around their eyes were 4.28 times more likely to have a stroke than people who did not have shingles.

We confirmed that in the general population, the risk for stroke increased after a zoster attack and additionally found that strokes after such attacks were more frequent than expected, Kang and colleagues wrote.

The team did not study how the virus might cause stoke, but other studies have found that it attacks the walls of blood vessels, causing damage and inflammation. This can cause blood vessels to close, blocking blood flow to the brain.

Kang's team found that people in the shingles group were more likely to have heart disease than people who did not have the infection. He said it may be possible that people who have signs of heart disease are less healthy and more prone to develop shingles.

While the mechanism by which shingles increases stroke risk remains unclear, the possibility of developing a stroke after a shingles attack should not be overlooked, he said.

He urged doctors treating shingles patients to be watchful for signs of strokes.

The findings may be a boost for Zostavax, a shingles vaccine made by Merck & Co.

A survey by the U.S. Centers for Disease Control and Prevention in July found only 6.7 percent of all people in the United States over age 60 had been vaccinated against shingles.