OBJECTIVE: The efficacy of balneotherapy in rheumatology remains unclear. We aimed to estimate its benefits and risks in rheumatology. METHODS: We conducted a systematic review of randomised trials assessing any European balneotherapy for a rheumatological indication in adults versus any control, on clinical outcomes. We searched PubMed, Cochrane Library, Embase and https://clinicaltrials.gov/ (up to 28 November 2023). We used the Cochrane risk of bias tool version 2, funnel plot and asymmetry tests. We used a random effects model with an inverse-variance weighting method for standardised mean difference (SMD) and risk ratio (RR). We used the Grading of Recommendations Assessment, Development and Evaluation approach for two primary outcomes, pain and quality of life (QoL) at 3 months, and two safety outcomes, withdrawal and any adverse event (AE). RESULTS: We included 29 trials in mechanical disorders, 9 in inflammatory diseases and 4 in fibromyalgia. The synthesis suggested a decrease in pain of a very low level of certainty (SMD: -0.72 (95% CI (-1.00
-0.44)), very serious risk of bias and of inconsistency, publication bias strongly suspected)
an increase in QoL of a very low level of certainty (SMD: 0.56 (95% CI (0.37
0.75)), very serious risk of bias and serious risk of inconsistency)
inconclusive results regarding the risk of withdrawal (RR: 0.75 (95% CI (0.46
1.20)), very serious risk of bias and serious risk of imprecision) and of AE (RR: 0.80 (95% CI (0.43
1.50)), serious risk of bias and of inconsistency and very serious risk of imprecision). CONCLUSION: The certainty of the effect of balneotherapy in rheumatology was very low. PROSPERO REGISTRATION NUMBER: CRD42023448206.