A Pilot Study on the Relationship Between Thermal Habits, Chronic Inflammation, and Arterial Stiffness in Young Adults

Atherosclerotic cardiovascular disease (ASCVD) progresses silently, making early prevention crucial. This pilot study examines the relationship between thermal habits, chronic inflammation-related proteins, and arterial stiffness in young adults. The study included 25 participants: 9 males (mean age: 21.78 ± 2.05 years) and 16 females (mean age: 21.0 ± 0.97 years). We analyzed hot bathing habits and measured plasma interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), heat shock protein 70 (HSP70), and brachial-ankle pulse wave velocity (baPWV). Plasma IL-6 levels were significantly lower in those with a habitual hot-tub bathing practice (p = 0.04 overall; p = 0.018 in females). In females, hsCRP tended to be lower in the immersion hot -tub bathing group, though the difference did not reach statistical significance (p = 0.08). No significant differences were observed in plasma hsCRP levels, plasma HSP70 levels and baPWV in the overall, male, or female groups. In females, IL-6 correlated with ABI (ρ = -0.543, p = 0.03), and baPWV negatively correlated with hot tub bathing duration (ρ = -0.562, p = 0.045). In conclusion, lifestyle interventions, especially habitual hot-tub bathing, may support ASCVD prevention. This practice is easily adopted in Japan and may improve skeletal muscle function without requiring dietary or exercise restrictions.