People who have had an attack of shingles involving the eyes may have a heightened risk of stroke for a year afterward, a study published Wednesday suggests.

Shingles is a painful condition caused by a reactivation of the virus that causes chickenpox, known as varicella-zoster virus. Once a person has had chickenpox, the virus goes into a dormant state, dwelling in the body’s nerve fibers.

Some people - including adults older than 50 and people with compromised immune systems, from conditions such as HIV - are at increased risk of having the virus reactivate and cause shingles.

Shingles usually begins with a burning pain or itch in one location on one side of the body, followed by a rash of fluid-filled blisters; in an estimated 10 percent to 20 percent of cases, people develop ophthalmic shingles, which involves the skin around the eye and sometimes the eye itself.

In the new study, Taiwanese researchers found that among adults with and without ophthalmic shingles, those who’d had the infection were more likely to suffer a stroke in the year after seeking shingles treatment.

Among 658 men and women with the infection, 8 percent had a stroke during the study period, versus just under 2 percent of 1,974 shingles-free adults the same age.

The researchers then accounted for a number of factors that could help explain the higher stroke rate - like age, and the presence of chronic health problems like high blood pressure, diabetes and heart disease. They found that ophthalmic shingles itself was still linked to a more than four-fold increase in the risk of stroke.

The findings, reported in the journal Neurology, do not prove that ophthalmic shingles causes strokes in some people. But they build on evidence linking shingles to stroke risk.

In a recent study, the same research team found that patients who had been treated for any form of shingles had a slightly higher rate of stroke over one year than a comparison group of people the same age - 1.7 percent, versus 1.3 percent. The link appeared particularly strong among people who’d had shingles affecting the eyes.

The bottom line for people who’ve had ophthalmic shingles is that they should do what they can to reduce their risk factors for stroke, senior researcher Dr. Jau-Der Ho, of Taipei Medical University, told Reuters Health in an email.

That, Ho said, includes not smoking, keeping blood pressure in check and, for people with diabetes, good blood sugar control.

It is possible that the shingles virus raises the longer-term risk of stroke in some people. Since the 1970s, Ho’s team notes, there have been reports of people suffering strokes soon after shingles infection - within about two months, on average.

Varicella-zoster virus is the only human virus known to replicate in arteries in the brain. It’s possible, according to Ho, that in some people, the virus does relatively milder blood vessel damage that does not immediately result in stroke, but accelerates any ongoing atherosclerosis - a build-up of artery-clogging plaques that can lead to stroke.

However, more research is necessary before any conclusions can be drawn, according to an editorial published with the report.

A major limitation of the study is that relied on a review of patient records, writes Dr. Gustavo A. Ortiz, a neurologist at the University of Miami School of Medicine.

The researchers used a national health insurance database to identify 658 adults who had been treated for ophthalmic shingles and compared each with three randomly selected, shingles-free patients of the same age and gender. Such studies can only point to an association between two variables - like shingles and stroke risk - and not whether one causes the other.

The study also lacked some key information on patients, Ortiz notes, such as whether they smoked or had atrial fibrillation, a heart-rhythm disturbance that can lead to stroke.

Another question is whether antiviral treatment for shingles might make a difference in longer-term stroke risk. Ho’s team found no evidence that ophthalmic shingles patients who received antiviral medication had a lower stroke risk than those who went untreated.

But again, Ho said, the study design does not allow firm conclusions. Controlled studies that follow patients over time are needed to see whether antiviral treatment affects long-term stroke risk, he said.

SOURCE: Neurology, online March 3, 2010.