Abstract
BACKGROUND: Bell's palsy (BP) is an idiopathic condition affecting the seventh cranial nerve, causing unilateral facial muscle paralysis. Conflicting reports exist on the impact of seasonal variations on BP, and limited systematic reviews have been conducted. In this study, a systematic review and meta-analysis of the BP literature was performed to assess the association between BP and the four seasons. METHODS: In accordance with PRISMA guidelines, a systematic search was performed using the PubMed, Google Scholar, and Web of Science databases to identify cohort studies reporting seasonal cases of idiopathic BP. Study quality and risk of bias were assessed via the Newcastle-Ottawa Scale (NOS). The associations between seasonal variations and the occurrence of BP were analyzed via a random effects model. RESULTS: Eight cohort studies involving 3,363 BP patients were included, with a slight male predominance (51.5%). The pooled mean age was 44.72 ± 19.6 years. Pooled proportions for each season were determined via subgroup analysis. Winter proportions were the highest at 0.27 (95% CI: 0.24-0.31; I (2) = 65.6%, p = 0.0048), followed by autumn at 0.26 (95% CI: 0.23-0.29; I (2) = 59.3%, p = 0.0161). The spring proportion was 0.24 (95% CI: 0.20-0.27; I (2) = 68.1%, p = 0.0026), whereas the summer proportion was 0.22 (95% CI: 0.19-0.25; I (2) = 61.5%, p = 0.0111). The test for subgroup differences showed (χ(2) = 6.62, p = 0.0850). CONCLUSION: BP cases were more common during colder months than during warmer months. Although no statistically significant association was found, this highlights the need for further studies across diverse climatic regions to clarify potential seasonal influences. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD42024623519, identifier: CRD42024623519.