The epidemiology of Guillain-Barré syndrome.

Population-based studies of Guillain-Barré syndrome (GBS) give crude average annual incidence rates varying from 0.4 to 1.7 per 100,000 population. The reported incidence is influenced by the diagnostic criteria adopted as well as the thoroughness of case-finding. Variations in these account for some of the lack of uniformity between different studies. Data from the Mayo Clinic based on National Institute of Neurological Disorders and Stroke diagnostic criteria and thorough ascertainment methods gave a crude incidence of 1.7 per 100,000 per year (x 10(-5]. Incidence was higher in females (2.3 x 10(-5] than males (1.2 x 10(-5] as well as in older compared to younger people (3.2 x 10(-5) over age 60 and 0.8 x 10(-5) under age 18, respectively). The disease reached a nadir after onset at 8 days on average, and the illness lasted an average of 12 weeks. Most patients (75%) recovered completely. Recent epidemiological studies of GBS suggest no clear secular trend. Incidence does fluctuate with time but not clearly with season. In virtually all studies "triggering" factors are implicated, but they appear to be diverse, making it less likely, from an epidemiological perspective, that a single antigen is of etiological importance in GBS.