Background and Aim: We report a population-based study conducted in Iceland to determine the incidence, clinical characteristics and prognosis of idiopathic chronic inflammatory demyelinating polyneuropathy (CIDP) during a 21-year period. Methods: Cases were identified from the records of all practicing neurologists in the country, the only neurology department in the country and both neurophysiology laboratories. All index cases met the 2010 European Federation of Neurological Societies/Peripheral Nerve Society criteria for CIDP. Results: Nineteen individuals fulfilled the diagnostic criteria during the study period. The average annual incidence was 0.3/100,000 (95% CI 0.04-2.47). There were 14 men (74%) in a gender ratio of 1:2.8. The mean age at diagnosis was 57 (range 19-81 years): women, 36 years and men, 63 years; p = 0.0006. The disease course was remitting-relapsing in 21% and chronic progressive or monophasic in 79%. The average length of follow-up was 6.9 years. The standardized mortality ratio for the 21-year study period was 0.9 (95% CI 0.3-2.2). Conclusion: We believe we have identified all diagnosed with CIDP in Iceland during a 21-year period. Many had no or only limited disease progression over the years and mortality is not increased compared with the general population.

We believe we have identified all patients diagnosed with GBS in Iceland during the study period, with an incidence comparable to recent studies from well-defined populations around the world. Our reported mortality is similar to or higher than other population-based studies. At follow-up, 13% of patients still required a walking aid, but most survivors (74%) had minor or no symptoms.

Background: Guillain-Barré syndrome is an immune-mediated acute inflammatory polyneuropathy that is associated with various triggers, including certain infections and vaccines. It has been suggested that both SARS-CoV2 infection and vaccination may be triggering factors for Guillain-Barré syndrome, but evidence remain equivocal. Here we conducted a population-based incidence study of Guillain-Barré syndrome spanning the three years immediately prior to and the two years during the pandemic. Methods: Cases were identified by searching a regional diagnostic database for the ICD-10 code for Guillain-Barré syndrome. Individuals who fulfilled the Brighton Criteria for Guillain-Barré syndrome were included. Information on clinical presentation, laboratory values, and vaccination status were retrieved from medical records. We calculated the incidence immediately prior to and during the pandemic. Results: The Guillain-Barré syndrome incidence rate was 1.35/100,000 person-years for the pre-pandemic period, and 0.66/100,000 person-years for the pandemic period (incidence rate ratio: 0.49; p = 0.003). Three cases were temporally associated with SARS-CoV2 infection, and one case each to the Astra Zeneca and Pfizer-BioTech COVID-19 vaccines. Conclusions: Our results show that the incidence of Guillain-Barré syndrome decreased during the pandemic. This is most likely due to decreased prevalence of triggering infections, due to social restrictions. Our findings do not support a causal relationship between Guillain-Barré syndrome and COVID-19.