The study is not the first to show an elevated stroke risk associated with shingles, but it is the first to quantify the risk, researchers say.
Compared to adults without shingles, those with the painful skin rash were about 30% more likely to suffer a stroke within a year of the attack. Patients who had shingles in and around an eye had four times the risk for stroke in the year following the episode.
"If a person is already at risk for stroke, they should be aware that their risk may be higher if they have had shingles," study researcher Jiunn-Horng Kang, MD, MSc, tells WebMD.
Anyone who has had chickenpox in childhood can develop shingles at some point in their lives.
In many people, the virus remains dormant in nerves. But in some, especially older people and those with compromised immune systems, it can reactivate as shingles.
The reawakened virus initially causes numbness, itching, severe pain, and even fever, headaches, and chills, followed by the blistering rash characteristic of shingles. The skin rash usually occurs within three to five days after symptoms begin.
Shingles can result in persistent pain lasting for months and even years after the rash has gone away.
The newly published study included nearly 8,000 adults treated for shingles between 1997 and 2001 and about 23,000 people matched for age and sex who had no history of shingles or stroke before 2001.
During the year following the shingles episode, 133 shingles patients (1.7%) and 306 people in the comparison group (1.3%) had strokes.
The shingles patients had a 31% increased risk for strokes of any kind and a nearly threefold increased risk for hemorrhagic strokes.
The study was published online today and will appear in the November issue of the American Heart Association journal Stroke.
Stress, Inflammation May Play Role
Varicella zoster virus-related blood vessel damage has been linked to stroke after shingles attacks, but this did not fully explain the high stroke risk seen in the study, Kang and colleagues wrote.
They added that the stress associated with shingles and the intense pain that can occur with outbreaks and following them could play a role, as could the inflammation that occurs with shingles outbreaks.
American Stroke Association spokesman Daniel Lackland, MD, says shingles patients and their doctors need to be aware of the new research.
Lackland is a professor of epidemiology and medicine at the Medical University of South Carolina in Charleston.
"This research needs to be confirmed, but it may be that shingles patients with risk factors for stroke need more aggressive monitoring and treatment than the average patient," he tells WebMD.
But he adds that the shingles-related stroke risk identified in the study is nowhere near as great as the risk associated with better-established stroke risk factors, like high blood pressure.
"The message doesn't change based on this study," he says. "Getting high blood pressure under control and treating other modifiable risk factors is what we have to focus on."
Early, aggressive treatment with antiviral drugs can lessen the length and severity of shingles attacks.
Kang says it remains to be seen if aggressive antiviral treatment can also lower stroke risk.
"This is a question we need to study," he says.