Abstract
This nationwide population-based ecological study investigated changes in the incidence of Bell's palsy (BP) in South Korea during the COVID-19 pandemic. Patients diagnosed with BP between January 2017 and December 2022 were analyzed. Considering the unique progression of the COVID-19 pandemic and corresponding public health responses in South Korea, the study period was divided into four phases: pre-COVID-19 (2017-2019), non-pharmaceutical intervention (NPI, 2020), nationwide vaccination (2021), and nationwide infection (2022). Poisson regression was used to calculate incidence rate ratios (IRRs) for each pandemic phase compared to the pre-COVID-19 baseline, adjusting for age and sex. Among 103 482 patients, BP incidence significantly decreased during the vaccination (IRR 0.96; 95% CI, 0.94-0.98) and infection (IRR 0.95; 95% CI, 0.93-0.97) phases (p < 0.001). These trends were more pronounced among women and older adults and did not correlate with national vaccination or infection rates. Our findings suggest that the incidence of BP did not increase during the COVID-19 era at the level of the general population nationwide. Further studies using individual-level data on COVID-19 infection and vaccination are needed to clarify their potential direct impact on BP incidence.