Guillain-Barré Syndrome (GBS) occurs throughout the world and at all ages. Numerous epidemiological studies have been conducted, and the reported incidence of GBS in various regions of the world ranges from 0.6 to 2.4 per 100,000 populations per year. Recently the Japanese GBS Research Project Team has commenced a nation-wide prospective survey of the incidence of GBS and this will be the first large-scale epidemiological study on GBS incidence in Japan using well-defined diagnostic criteria. However, a few years ago, I conducted a detailed epidemiological study in Isehara city, Kanagawa prefecture, where Tokai University School of Medicine is located. Isehara city is situated in the countryside about 50 km west of the center of Tokyo, and has an area of 55.5 km2. This survey was carried out in our l000-bed tertiary care university hospital from January 1, 1990 to December 31, 1995. In addition, I sent inquiries to all hospitals and clinics in Isehara and neighboring cities. I could not include patients under 10 years old because their medical records were not available to me. Diagnosis of GBS was made according to the NINCDS clinical criteria of GBS.

During the period 1990 to 1995, I identified a total of seven GBS patients who were residents in Isehara city. Five were men and two were women, with ages ranging from 27 to 48 (mean ± SD : 36 ±9). During the study period, the total population over 10 years of age in Isehara city increased from 76,981 in 1990 to 86,769 in 1995. Based on the average population during the 6 years, the mean annual incidence of GBS was calculated as 1.41 cases per 100,000 population. Sex-specific rates were 1.95 for men and 0.83 for women. Although estimated incidences of GBS vary in different regions, studies based on strict use of NINCDS criteria, including mine, suggest that GBS has about the same incidence all over the world of around 1 case per 100,000 populations per year [1]. In my study I found a higher incidence in males than in females, and this is also consistent with data from most other studies.

Recently many GBS patients with predominantly axonal degeneration, known as AMAN or ASMAN, have been reported from northern China. At the 4th International Symposium of GBS, which was held in Miami in 1996, I presented my own data and reported that GBS patients in Japan tended to show the so-called ''axonal form'' more frequently than did western patients. About 20 percent of GBS patients were diagnosed as axonal form based on the electrodiagnostic criteria, and the remaining 80% of patients had the demyelinating form, which is frequently encountered in western countries. The reason for this high frequency of axonal form in Japan is not yet clear, but Japanese GBS patients showed a higher frequency of seropositivity to Campylobacter jejuna, compared with western patients. So I speculate that the higher frequency of axonal form in Japanese GBS patients may be related to the higher frequency of antecedent Campylobacter jejuni infection. In addition, demographic, geographic and genetic factors are also suspected to play an important role in the development of axonal form of GBS in Japanese patients.

I think that the results of the nation-wide prospective survey by the Japanese GBS Research Project Team will give us more precise information about the incidence of GBS in Japan and the characteristics of Japanese GBS, and should be very helpful as a guide for future clinical research on GBS in Japan.