Infections Such as Pneumonia and Herpes May Heighten Stroke Risk
By Allison Gandey
Medscape Medical News
November 11, 2009 — Investigators suggest that infections increase the risk for stroke through an aggregate effect on vascular inflammation. The results, published online November?9 in the Archives of Neurology, suggest a new modifiable risk factor for stroke.
"If our results are confirmed, it opens the path to new ways to prevent strokes, including vaccinations or even antibiotics," lead investigator Mitchell Elkind, MD, from Columbia University in New York City, told Medscape Neurology. "A great deal of research has provided evidence of an association between various infections and risk of stroke and heart attacks, so we were not surprised by the findings," he added, "but one is always happy to see a hypothesis confirmed."
Researchers studied more than 1600 participants from the Northern Manhattan Study. This ongoing cohort study is designed to investigate stroke incidence, risk factors, and predictors of severity and outcome. Participants have been followed for a median of 8 years.
In this new analysis, investigators wanted to determine the association between a composite measure of serologic test results for common infections, called the infectious burden index, and risk for stroke. They assessed Chlamydia pneumonia, Helicobacter pylori, cytomegalovirus, and herpes simplex virus?1 and 2.
Dr. Elkind and his team found that each individual infection was positively — although not significantly — associated with stroke risk after adjustment for other risk factors.
The infectious burden index was associated with an increased risk for all strokes. The hazard ratio (HR) per SD was 1.39 (95% confidence interval [CI], 1.02?- 1.90) after adjustment for demographics and risk factors. Results were similar after excluding patients with coronary disease (adjusted HR, 1.50; 95% CI, 1.05?- 2.13).
Stroke Risk Associated With Positive Serologic Test Results Serologic Test Adjusted Hazard Ratio(95% Confidence Interval)
Chlamydia pneumonia 1.30 (0.75 - 2.25)
Helicobacter pylori 1.13 (0.68 - 1.89)
Cytomegalovirus 2.19 (0.84 - 5.70)
Herpes simplex virus?1 1.35 (0.59 - 3.07)
Herpes simplex virus?2 1.59 (0.91 - 2.76)
Dr. Elkind pointed out that his group did not include all infections and did not assess periodontal problems, for example.
He said that although common infections appear to be linked to stroke, there is not likely a single "stroke bug" but rather an association, perhaps through a cumulative burden of infection. "These results need to be validated in other populations before they can be translated into clinical practice," he said.
Another study, published in the November issue of Stroke (2009;40:3443), linked herpes zoster to stroke. The epidemiologic study suggested that infection increases the risk for ischemic and hemorrhagic events.
Investigators showed that the risk for stroke increased by 30% after a herpes zoster attack. The risk is even higher, approximately 4-fold, if the attack involves the eye (herpes zoster ophthalmicus).
There is still no established therapy to prevent herpes zoster infection, also known as shingles, lead investigator Jiunn-Horng Kang, MD, from the Taipei Medical University Hospital in Taiwan, told Medscape Neurology last month, when the Stroke study was released online. Early antiviral therapy could play an important role, he noted, but this role still needs to be studied.
"From the practical view, physicians should be aware of the potential elevated risk of stroke when they care for patients with acute herpes zoster attack," Dr. Kang said. "Furthermore, careful monitoring and management of the pre-existing risk factors for stroke, such as hypertension, hyperlipidemia, and diabetes mellitus, could be helpful in reducing the risk for stroke."
This study was funded by the National Institutes of Health. Dr. Elkind and Dr. Kang have disclosed no relevant financial relationships.
Arch Neurol. Published online November 9, 2009.
