Geochemical Perspectives Intercept Therapeutic Properties of Saturnia Thermal Waters: A Retrospective Cohort Study

Background: Saturnia thermal waters, characterized by unique calcium-sulfate composition and high hydrogen sulfide (H₂S) concentrations, have been traditionally used for therapeutic purposes. Despite emerging molecular evidence of H₂S's immunomodulatory properties, the relationship between specific geochemical parameters and measurable health outcomes remains poorly quantified. This study aimed to determine the association between H₂S concentration and quality of life outcomes under different exposure protocols. Methods: We conducted a retrospective analysis of medical records from adult patients (≥18 years) who underwent balneotherapy at Saturnia Thermal Center between January 2016 and December 2023. Participants (N=190) were stratified into acute (2-3 hours, n=114) and sustained exposure (3-14 days, n=76) cohorts. Primary outcomes included changes in SF-36 Physical Component Summary (PCS) and WHOQOL-BREF physical health domain scores. Secondary outcomes comprised pain reduction (Visual Analog Scale) and dermatological life quality (DLQI). Geochemical profiles, including H₂S concentration, pH, mineral content, and temperature, were measured daily. Multiple regression analyses and Pearson correlations assessed relationships between geochemical parameters and health outcomes, adjusting for age, gender, and treatment duration. Results: The sustained exposure cohort demonstrated greater improvements in SF-36 PCS (mean change = 11.7 [95% CI: 9.8, 13.6], d = 0.67 [95% CI: 0.54, 0.80]) compared to acute exposure (mean change = 7.3 [95% CI: 5.9, 8.7], d = 0.41 [95% CI: 0.32, 0.50]). H₂S concentration emerged as the strongest predictor of outcome improvement (β = 0.28 [95% CI: 0.15, 0.41], R² = 0.458), with significant correlations observed for both pain reduction (r = -0.42 [95% CI: -0.51, -0.32]) and quality of life enhancement (r = 0.45 [95% CI: 0.35, 0.55]). No serious adverse events were reported during the study period. Conclusions: Higher H₂S concentrations in Saturnia thermal waters significantly correlate with improved physical health outcomes, particularly during sustained exposure protocols. Future randomized controlled trials should investigate optimal exposure durations and H₂S concentration thresholds for specific therapeutic applications.