Characteristics of cold-induced vasodilation among Tibetans and Han Chinese at high altitudes.

Background: Cold-induced vasodilation (CIVD) reduces the risk of local cold injuries. There are obvious differences in CIVD characteristics among different ethnic groups. This study aimed to compare cold tolerance manifested through CIVD responses in indigenous Tibetans and Han residents in Tibet.

Methods: A total of 12 Tibetans and 10 Han individuals (residence duration at high altitude > 5 years) from high altitudes were recruited in the study. The CIVD test was performed by immersing the participants' middle finger of the non-dominant hand in cold water (0 ℃) for 30 min followed by recovery for 10 min at a temperature of 25 ± 1 ℃. During the CIVD tests, the participants provided perceptual responses for the immersed hand every 5 min. The participants completed their baseline questionnaires and physiological assessments before the start of the CIVD test, and they completed their hematological tests the following morning.

Results: Compared with Hans at high altitude, Tibetans had higher minimum temperature (T_min), maximum temperature (T_max), and Resistance Index for Frostbite (RIF) scores (p < 0.05), and warmer perceptual responses (p < 0.05). We found that red blood cell (RBC) count, hemoglobin (HGB) and hematocrit (HCT) were positively correlated with onset time (Δt_onset), peak time (Δt_peak), frequency of CIVD waves (CIVD_waves), and negatively correlated with T_min, T_max, mean finger temperature (T_mean) in the general population (p < 0.05), whereas these correlations were not observed in the Tibetan and Han populations (p > 0.05). However, the basophil percentage (BAS%), neutrophil percentage (NEU%) and γ-glutamyl transpeptidase (GGT) levels (p < 0.05) correlated with the RIF score in Han population.

Conclusion: Compared with Hans at high altitude, indigenous Tibetans demonstrated superior local cold resistance phenotypes in vasomotor regulation, evidenced by their distinct CIVD and perceptual responses. Hematological and biochemical parameters, erythrocytosis is a critical determinant of local cold tolerance at high altitude in the general population. BAS%, NEU%, and GGT are related to local cold tolerance in Han residents.