To summarize the evidence on the association between weight status and the development of Guillain-Barré Syndrome (GBS).

Guillain-Barré syndrome (GBS) is an immune-mediated neuropathy that, due to its inflammatory basis, has been associated with elevated body mass.

We searched 5 databases (PubMed, Embase, Scopus, Web of Science and Google Scholar) until April 2024. We included observational studies that evaluated the association between BMI (underweight, overweight, obese, and excess weight) and GBS. A meta-analysis using a random-effects model to estimate pooled effects was planned for each outcome and a narrative synthesis when this was not possible. Normal weight was the comparator and the outcome was diagnosis or prognosis of GBS. The New casttle-Ottawa scale was used to assess the risk of bias and GRADE criteria were used to identify the certainty of evidence.

Five studies (4 cohorts and 1 conference abstarct) were included. Regarding diagnosis, a meta-analysis of 3 cohort studies (5,422,788 patients) demonstrated a significant increased risk of GBS in overweight (HR: 1.37; 95% CI: 1.07-1.76) and obese patients (HR: 1.75; 95% CI: 1.26-2.42); also, other cohort study reported that for each unit of BMI the risk of GBS did not increase (HR: 1.00; 95% CI: 0.88-1.13). Regarding GBS prognosis, the conference abstract reported that have underweight or overweight/obese was associated with greater disease severity (OR: 0.324; 95% CI: 0.10-1.0). Additionally, all studies reported a low risk of bias.

With moderate certainty, being overweight and having obesity were associated with an increased risk of GBS. In addition, we found that an altered weight status could be a prognostic factor for GBS severity. However, further studies analyzing this association are needed to confirm these results.