Age-related patterns in tongue thermal response to cold stimulus assessed by infrared thermography

Tissue surface temperature may be influenced by physiological processes related to microcirculation and vascular regulation. Due to its rich vascularisation and thin epithelial layer, the tongue may serve as a sensitive site for assessing dynamic thermal responses. This study aimed to quantitatively evaluate the tongue's response to a cold stimulus using infrared thermography and to analyse its relationship with age in healthy adults. An observational study was conducted in 117 volunteers aged 18-64 years. Tongue temperature was measured at baseline, immediately after cold exposure (20 ml of water at 8 °C for 60 s), and after 2, 5, and 10 min. Baseline temperature, as well as absolute and relative indices of temperature recovery, were analysed across three predefined regions of interest. A statistically significant association was observed between age and both baseline tongue temperature (r = - 0.21, p = 0.024) and post-stimulus thermal dynamics, including temperature changes 2 min after stimulation (r = 0.33, p = 0.0002) and relative recovery indices (W₂-W₁₀: r = 0.29-0.30, p ≤ 0.002). Younger individuals exhibited a greater immediate decrease in temperature, whereas older participants showed higher relative temperature recovery indices; however, this may be partly influenced by differences in the magnitude of the initial temperature decrease. No significant correlations were found between thermal parameters and basic physiological or anthropometric variables. These findings suggest a potential association between age and selected thermal parameters; however, this relationship was not confirmed after accounting for the repeated-measures structure of the data in the mixed-effects model.