A pilot study on the relationship between thermal habits, chronic inflammation, and arterial stiffness in young adults

Twenty-five participants were included: 9 males (mean age: 21.78 ± 2.05 years) and 16 females (mean age: 21.0 ± 0.97 years). We assessed 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). IL-6 levels were significantly lower among habitual hot-tub bathers (p = 0.04 overall; p = 0.018 in females). In females, hsCRP tended to be lower with immersion bathing (p = 0.08). No significant differences were observed in hsCRP, HSP70, or baPWV in the overall, male, or female groups. In females, IL-6 negatively correlated with ABI (ρ = -0.543, p = 0.03), and baPWV negatively correlated with bathing duration (ρ = -0.562, p = 0.045). These findings suggest that habitual hot-tub bathing, a culturally embedded and easily implemented habit in Japan, may serve as a lifestyle intervention to reduce inflammation and support ASCVD prevention in young adults.