The role of age-sex interaction in the development of post-herpetic neuralgia

Post-herpetic neuralgia is the most frequent complication of herpes zoster and affects up to 30% of patients. Increased age is a well-recognized risk factor, while the role of gender is highly uncertain. Little research has been performed into a possible combined effect of age and sex in post-herpetic neuralgia. The objective of the study was to study the role of age and sex and their combined effect in the development of post-herpetic neuralgia. This retrospective study enrolled adult subjects with at least one episode of herpes zoster in the previous 10 y. A questionnaire on the patient's socio-demographic, anamnestic and clinical characteristics was administered by general practitioners. Multivariable logistic regression was used to detect relationships between post-herpetic neuralgia and age, sex and their interaction. Fifty-nine of 272 patients reported post-herpetic neuralgia: a prevalence of 21.7%. Subjects with post-herpetic neuralgia (mean age 70.9 years) were significantly older (P = .001) than those without (64.2 years), the standardised mean difference being 0.5; no significant between-sex association was revealed (P = .96). A fully adjusted multivariable logistic analysis, however, revealed a highly significant (P = .007) age-sex interaction, with an odds ratio of 0.92; this also showed that older males were more likely to report post-herpetic neuralgia than younger males, while no obvious age-associated pattern was observed among females. We discerned a significant age-by-sex interaction in the development of post-herpetic neuralgia, which suggests that the effect of age on the development of this condition may differ between men and women.