Shingles, also known as herpes zoster, is caused by the reactivation of the varicella-zoster virus, which also causes chickenpox. After a person recovers from chickenpox, the virus stays dormant in the body. Years later, it can reactivate as shingles. About 1 in 3 people in the United States will develop shingles during their lifetime.
Shingles usually affects a localized area on one side of the face or body and causes a painful rash that can take 2 to 4 weeks to heal. The most common complication of shingles is postherpetic neuralgia (PHN), a condition where the nerve pain persists even after the rash has cleared.
Another serious complication that can sometimes occur with shingles is a stroke. Shingles can cause inflammation of the blood vessels, which can then lead to blood clots forming. If a blood clot travels to the brain, it can block blood flow and cause a stroke.
How Common is Stroke After Shingles?
Several studies have found a link between recent shingles infection and increased stroke risk:
– A Taiwanese study published in 2015 followed 8,876 adult shingles patients for 3 years. It found that the risk of stroke was 39% higher in the first year after a shingles diagnosis compared to a control group without shingles. The stroke risk then declined over the next 2 years but remained elevated.
– A 2009 U.S. study examined Medicare claims data for 106,600 people aged 65 and older diagnosed with shingles. In the first year after shingles, the stroke rate was 10.7 per 1,000 person-years compared to 8.2 per 1,000 person-years for those without shingles – a 31% increased risk.
– Research from Taiwan published in 2010 found the risk of stroke was 1.31 times higher in the first year after shingles and remained elevated for more than 3 years. The stroke risk was highest in the first 3 months after shingles.
– A Danish study published in 2016 found the risk of stroke doubled within the first week after shingles and remained elevated for up to 12 months after shingles. The stroke risk was highest in the first 2 weeks.
While the numbers vary across studies, the research overall shows between a 31% to 100% increase in stroke risk in the months immediately following shingles. The stroke risk is highest within the first 1 to 3 months after the shingles rash occurs but may remain elevated for a year or longer.
Age Differences in Stroke Risk
The risk of stroke after shingles infection seems to increase with age:
– In the Taiwanese study, the stroke risk was 1.42 times higher for shingles patients ages 50-64. It jumped to 2.42 times higher for those ages 65-74.
– An Israeli study found that for patients aged 18-45 years old, there was no increased stroke risk with shingles. However, the risk was over 3 times higher after shingles for those ages 46-75.
– Research from Denmark showed the greatest impact of shingles on stroke risk was in those over age 70. The stroke rate after shingles doubled for ages 50-69 but increased over 5-fold for those over age 70.
Therefore, while shingles can increase stroke risk for adults of any age, the effect seems most pronounced in older individuals over age 70.
Who is at Highest Risk of Stroke After Shingles?
While anyone who gets shingles is at increased risk of stroke, some factors place certain groups at even higher risk:
Women
Research has consistently shown that women face a greater risk of stroke after shingles than men:
– In the Taiwanese study, women had an 84% higher risk while men had a 29% higher risk of stroke after shingles.
– The Medicare data study found a 35% increased stroke risk for women after shingles compared to 24% for men.
– The Israeli research showed the stroke risk after shingles doubled for women but increased just 31% for men.
The reasons for the gender difference are unclear. One theory is that women tend to have more robust immune responses which could contribute to greater vascular inflammation after a shingles infection.
Those with Existing Risk Factors
People who already have stroke risk factors seem to be more vulnerable to the effects of shingles:
– A U.K. study found the impact of shingles on stroke risk was greatest in those who already had high blood pressure, diabetes, or heart disease. For those with these conditions, the stroke rate increased 350% after shingles.
– Research on over 1 million U.S. veterans showed shingles had little effect on future stroke risk for those without cardiovascular risk factors. However, for those with risk factors, shingles increased the 1-year stroke risk by 60%.
So shingles may act as a trigger to produce a stroke in those who are already predisposed due to existing medical conditions. Controlling conditions such as high blood pressure and diabetes may help reduce the stroke risk after a shingles infection.
Those with Severe Shingles Infections
The severity of the shingles infection also seems to play a role. Studies have found:
– A higher increased stroke risk in those who suffer from shingles infections affecting larger areas of the body surface compared to more localized shingles cases.
– Up to 4 times higher stroke risk following cases of shingles ophthalmicus, where the virus affects the eye and facial area. This is likely due to more widespread vascular inflammation.
Therefore, aggressive forms of shingles that are widespread or affect critical areas like the eyes appear to produce greater vascular effects and further increase the probability of a subsequent stroke.
Possible Biological Mechanisms
Researchers theorize several biological mechanisms by which shingles is linked to increased stroke risk:
Vascular Inflammation
The shingles virus can cause inflammation of the blood vessels (vasculitis), making them more prone to clot formation. Autopsies of shingles patients have shown inflammation of the arteries in the brain.
Damage to Arterial Walls
Shingles may damage the lining of the arterial walls, allowing cholesterol plaques to form. Plaques can break off and cause blood clots leading to stroke.
Immune Activation
Shingles leads to activation of the immune system including increased levels of pro-inflammatory cytokines and immune cells like neutrophils and T cells. This heightened immune response may promote clot formation and atherosclerosis.
Viral Spread to Arteries
While still debated, some research indicates the shingles virus itself may spread from nerve tissues to infect arterial walls, which could trigger blood clots.
So in various ways, shingles appears to create dysfunction and inflammation in the arteries that can predispose to blood clots traveling to the brain. More research is needed to confirm the exact mechanisms.
Preventing Stroke after Shingles
While not completely preventable, there are some steps that may help lower the risk of stroke following shingles:
Get Treated Promptly
Quickly starting antiviral medications when shingles symptoms begin can help reduce the severity and duration of the infection. This may minimize the impact shingles has on increasing stroke risk.
Control Risk Factors
Carefully controlling pre-existing conditions like high blood pressure, diabetes, and high cholesterol may reduce susceptibility to stroke after getting shingles.
Avoid Dehydration
Staying well-hydrated can help prevent blood clots. Shingles can cause fluid loss from fever, sweating, and impaired fluid intake due to pain. Drink plenty of non-caffeinated fluids.
Ask About Aspirin
For older adults with shingles, short-term aspirin therapy may help reduce inflammation and prevent clot formation. However, check with your doctor first as aspirin can increase bleeding risk.
Monitor for Signs
Watch for potential stroke warning signs that require urgent medical attention, like face drooping, arm weakness, and speech difficulty. Acting quickly can minimize stroke damage.
While having shingles may put you at increased risk of stroke, focusing on early treatment, controlling medical conditions, and staying aware of stroke symptoms can help lower your chances.
Conclusion
In summary, research shows there is an elevated risk of stroke in the weeks and months following an infection with shingles. The increase in stroke risk may be as high as 2 to 5 times normal, especially in the first 1 to 3 months after shingles occurs.
Older adults over age 70 and women seem to be at greatest risk of stroke after shingles. The shingles virus likely leads to inflammation and dysfunction of the arteries that can promote blood clot formation. Prompt treatment and controlling risk factors may help reduce chances of stroke. But anyone who has had shingles should be alert for potential warning signs of stroke and seek immediate medical care if they develop.