Radon balneotherapy in rheumatologic diseases: potential mechanisms and implications for cardiovascular autonomic control and inflammation.

Radon balneotherapy, a form of low-dose radiation treatment, has been utilized for decades in managing rheumatologic diseases, particularly in Central Europe and parts of Asia. Despite ongoing debate about its efficacy, developing research suggests that low-dose exposure to radon may exert anti-inflammatory and analgesic effects, with potential implications for musculoskeletal and cardiovascular health. This narrative review aims to synthesize current knowledge on the biological mechanisms underlying radon therapy, evaluate clinical evidence for its efficacy in rheumatologic conditions, and explore its potential impact on cardiovascular health. Risks, controversies, and regulatory restrictions are also addressed. Preclinical studies indicate that radon therapy modulates oxidative stress responses, immune signalling cascades, and pro-inflammatory cytokine profiles, thereby influencing tissue homeostasis and pain perception. Clinically, benefits have been observed in patients with rheumatoid arthritis, ankylosing spondylitis, and osteoarthritis, particularly with respect to pain alleviation, functional improvement, and quality of life. However, heterogeneity in treatment protocols, study quality, and confounding factors such as the use of heat, carbon dioxide, and/or other concurrent modalities limit generalizability and attributability. Evidence regarding cardiovascular safety remains sparse but suggests that low-dose exposure may have neutral or even protective effects under specific physiological conditions. In summary, radon balneotherapy may have a complementary role alongside other modalities like heat and negative air ions. However, the isolated therapeutic efficacy, long-term safety profile, and cardiovascular implications of radon balneotherapy remain insufficiently characterized. Higher quality multi-armed randomized controlled trials and isolated mechanistic investigations are needed to better delineate its biological mechanisms, optimize protocols, and define its clinical niche.