Patients experiencing the first signs of shingles may have a higher risk of stroke. However, this risk can be reduced if they're treated with oral antiviral drugs, according to a new study published online in Clinical Infectious Diseases.

According to the study, conducted by researchers at the London School of Hygiene and Tropical Medicine, patients had a particularly high risk of stroke during the first six months after the appearance of shingles symptoms. They had an even greater risk if their symptoms included a rash around the eyes, according to the study background.  

Shingles, or herpes zoster, is a painful skin rash caused by the same virus that causes chickenpox. After a person has had chickenpox, the virus becomes dormant in the nerves of the body, but it can become active again, often years later, and cause shingles, according to the National Center for Biotechnology Information (NCBI). Other symptoms include blisters and sores on some parts of the body, fever and chills, joint pain, and swollen glands.

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Doctors don't know why the virus reactivates in some people, but shingles can affect anyone, particularly those ages 60 and older, those who had chickenpox before age 1, and those with a weakened immune system, according to the NCBI.

“[Shingles] is a significant public health problem in aging populations, affecting 1 million Americans” and about 90,000 people ages 60 and older in the U.K. every year, the study authors wrote. 

The study results demonstrate the need for shingles vaccination programs and the importance of prescribing antiviral drugs in an effort to reduce the risk of stroke among shingles patients, the researchers concluded.

Who Is at Risk?

Researchers examined 6,584 patients across 600 medical practices in the U.K. who had experienced the initial symptoms of shingles and had suffered a stroke for the first time. Researchers also looked at the use of antiviral treatment among these patients to understand how it might affect stroke risk.   

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“Previous studies have suggested that risk of stroke is increased following acute shingles. However, the results of these studies could be affected by differences between people who develop shingles and those who do not,” said lead study author Sinéad Langan, Ph.D., in an interview with Healthline. “We removed the effect of these differences by comparing the risk of stroke in the time period after the patient had shingles to time periods when the patient did not have recent shingles.”

Researchers found that patients had a 63 percent higher stroke risk in the first four weeks following a shingles episode, compared with the patient's baseline risk. A patient’s increased risk slowly diminished over the following six months.

Oral antivirals were given to 55 percent of study participants. Estimates of stroke within the first four weeks “were nearly double in those not receiving antiviral therapy compared with those receiving treatment,” the study authors wrote. “Among individuals treated with oral antivirals, the only period with increased rate of stroke compared with baseline was five to 12 weeks post [shingles].”

Researchers also found that the risk of stroke was up to three times higher five to 12 weeks after the appearance of shingles among patients with a rash affecting the skin around their eyes (zoster ophthalmicus), compared with their baseline risk.

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Antiviral drugs can help reduce pain, prevent complications, and shorten the course of the disease. These medicines are usually taken orally, but some people need the drug to be administered intravenously, according to the NCBI. Other medicines used to treat shingles include antihistamines, pain medicines, and certain creams containing capsaicin to reduce pain.

"The relatively low prescribing rates of antiviral therapy in U.K. general practice after developing shingles need to be improved," Langan said.

Preventing Shingles to Prevent Stroke

“It is important to study the association between shingles and risk of stroke, as an effective vaccine is now available which can reduce the risk of shingles and hence may reduce the risk of stroke,” Langan said.

The FDA-approved herpes zoster vaccine Zostavax is available for adults ages 60 and older and is the best way to prevent shingles, according to the Centers for Disease Control and Prevention (CDC).

Learn More About the Shingles Vaccine »

Unfortunately, very few people take advantage of this vaccination, Langan said.

“Our previous research showed that vaccine uptake is very low (3.9 percent) in the older U.S. population and is particularly low in specific patient subgroups,” Langan said. “As the vaccine is effective in routine use, efforts are needed to increase vaccine use.”

While the CDC does not have any recommendations for routine use in people ages 50 through 59, the vaccine has been approved by the FDA for people in this age group. Those who have had shingles can still get the shingles vaccine, but the CDC recommends waiting until the shingles rash has disappeared before getting vaccinated.  

According to the CDC, you should not get the herpes zoster vaccine if you think you might be pregnant; have a weakened immune system due to certain drugs, such as steroids; are undergoing cancer treatment; or have a condition or disease, such as HIV/AIDS, that affects the immune system.

If you have severe allergies to gelatin or the antibiotic neomycin, the CDC recommends that you talk to your doctor before getting vaccinated.