The impact of the COVID-19 pandemic on the incidence and clinical profiles of Guillain-Barré syndrome in Japan

Since the coronavirus disease 2019 (COVID-19) pandemic began in 2020, several studies from various countries have described changes in the epidemiology of Guillain-Barré syndrome (GBS); however, it remains unclear whether the incidence and clinical profiles were altered by the pandemic. This study aimed to elucidate the impact of the COVID-19 pandemic on the epidemiology and clinical profile of GBS in Japan. We conducted a nationwide survey on the incidence of GBS between 2017 and 2022, encompassing the pre-pandemic [2017‒2019] and pandemic [2020‒2022] periods. Questionnaires were sent to the neurology and paediatrics departments at hospitals throughout Japan. A primary questionnaire was used to estimate the number of patients and incidence, and a second questionnaire was administered to collect detailed clinical information. The annual number of newly diagnosed GBS cases and their incidence were estimated at 1,885 (95% confidence interval [CI], 1,766‒2,004) and 1.49 (95% CI, 1.40‒1.58) per 100,000 population, respectively, during the pre-pandemic, 1,603 (95% CI, 1,463‒1,743) and 1.28 (95% CI, 1.17‒1.39) per 100,000 population during the pandemic periods; the relative risk for GBS incidence during the pandemic period was 0.91 (95% CI, 0.83‒0.99; 9% reduction). Detailed clinical profiles were available for 2,623 patients (1,420 during the pre-pandemic period and 1,203 during the pandemic period). Compared with patients in the pre-pandemic period, those diagnosed during the pandemic period were older (median age, 56 years vs. 53 years; P = 0.02), had a higher proportion of cases without antecedent infectious episodes (38.2% vs. 24.5%; P < 0.0001), longer time to reach nadir (median, 8 days vs. 7 days; P = 0.0418), and higher frequency of the demyelinating subtype of GBS (37.8% vs. 32.6%; P = 0.0068). No significant differences were observed in the outcomes at 6 months post-onset. The Japanese national registry data showed a markedly reduced number of Campylobacter-related enteritis cases following the pandemic. This study demonstrated a decrease in the overall incidence of GBS during the earlier phase of the COVID-19 pandemic in Japan. The increased number of GBS cases without infectious episodes or demyelinating subtypes during the pandemic period may be caused by reduced exposure to conventional infectious triggers of GBS, such as C. jejuni and increased asymptomatic COVID-19-related demyelinating GBS.