Risk factors for postherpetic neuralgia.

BACKGROUND: The risk factors for postherpetic neuralgia (PHN), the most common complication of herpes zoster, have not been well established.

OBJECTIVE: To elucidate the risk factors for PHN.

METHODS: Automated medical, claims, and pharmacy records of a health maintenance organization were used to identify cases of PHN and obtain data on risk factors. A case-base design was used to assess the impact of various patient, disease, and treatment factors on the prevalence of PHN 1 and 2 months after developing zoster.

RESULTS: There were 821 cases of herpes zoster that met all eligibility criteria. The prevalence of PHN more than 30 days after onset of zoster was 8.0% (95% confidence interval [CI], 6.3%-10.1%) and 4.5% (95% CI, 3.2%-6.2%) after 60 days. Compared with patients younger than 50 years, individuals aged 50 years or older had a 14.7-fold higher prevalence (95% CI, 6.8-32.0) 30 days and a 27.4-fold higher prevalence (95% CI, 8.8-85.4) 60 days after developing zoster. Prodromal sensory symptoms and certain conditions associated with compromised immunity were also associated with PHN. Systemic corticosteroids before zoster and treatment of zoster with acyclovir or corticosteroids did not significantly affect the prevalence of PHN.

CONCLUSIONS: Increased age and prodromal symptoms are associated with higher prevalence of PHN 1 and 2 months after onset of zoster. Overall, systemic acyclovir appears not to confer any protection against PHN, although benefit among elderly patients cannot be excluded.