A clinical diagnosis of herpes zoster ophthalmicus is often accurate, but HZO may masquerade as other conditions. PCR testing can help clinch the diagnosis and also be used to differentiate herpes zoster and herpes simplex. Photo: Alan Kabat, OD. Click image to enlarge.

Recent studies have determined an increased rate of stroke following herpes zoster infection, and herpes zoster ophthalmicus (HZO) in particular. However, experts pointed out in a newly published Eye paper that these studies didn’t control for social factors contributing to stroke, such as geographic location, income and education. Additionally, because conditions predisposing patients to vascular disease, such as smoking and obesity, are significantly more common in those with herpes zoster, controlling for social factors is key.

In order to validate the association between HZO and stroke, researchers rigorously controlled for both medical comorbidities and social factors, including geographic area, income, health-care usage and education. They used a two-part approach, consisting of a retrospective case-control study to estimate the hazard for stroke, and a self-controlled case series to compare the incidence of stroke prior to and after HZO diagnosis.

The case-control study included 25,720 cases and 75,924 controls from a nationwide U.S. administrative medical claims database. The researchers reported that 6.7% of cases and 6% of controls had strokes, demonstrating an 18% increased risk of stroke within one the year post-HZO period.

In the case series, they found that the risk for stroke was highest (1.58) in the month immediately following an HZO episode versus any other time range. Risk was higher still when assessing more distal time points prior to HZO diagnosis.

“After carefully controlling for stroke risk factors, our study confirms the association between HZO and stroke with the highest risk being in the immediate month after diagnosis,” the researchers concluded in their Eye paper. “Confirming this link between HZO and subsequent stroke has important implications for both treatment of the reactivated viral illness and prevention of stroke.”