Findings differ from earlier results

EDITOR—The article by Helgason et al provides new data about the prevalence of postherpetic neuralgia in Iceland.1 Their findings differ markedly in some respects from earlier retrospective findings. Two points in particular are at variance with British and American studies. The first is the proportion of patients with herpes zoster who develop postherpetic neuralgia and its duration. The Icelandic values are lower in both categories than those previously published from other countries.

A datum that is unfortunately missing from all studies is the age at which chickenpox, and therefore immunity, was acquired. It is well known anecdotally that postherpetic neuralgia is both rarer and less severe in people born on the Indian subcontinent; and there is considerable evidence that chickenpox occurs at a later age in this population.2 Most doctors working in pain clinics have seen patients with severe postherpetic neuralgia of 20 or more years' duration. Most such patients have had their herpes zoster when they were younger than 50 years.

The second point is that the intensity of postherpetic neuralgia pain is rated as considerably more severe by most European and North American sources than it is by Helgason et al. The mean visual analogue pain intensity score of 246 successive patients attending our centre for pain relief was 86.2 at presentation, with 142 patients having a score of over 90 (L Cossins et al, fifth international congress on the pain clinic, Jerusalem, 1992). Although herpes antibody titres are probably a guide to the severity of herpes zoster and postherpetic neuralgia, this cannot be performed on whole populations. It would be interesting to speculate, especially in view of the evidence from the Indian subcontinent, whether the age at …