The effect of ethnicity on the vascular responses to cold exposure of the extremities

Purpose

Cold injuries are more prevalent in individuals of African descent (AFD). Therefore, we investigated the effect of extremity cooling on skin blood flow (SkBF) and temperature (T _sk) between ethnic groups.

Methods

Thirty males 10 Caucasian (CAU), 10 Asian (ASN), 10 AFD] undertook three tests in 30 °C air whilst digit T _sk and SkBF were measured: (i) vasomotor threshold (VT) test—arm immersed in 35 °C water progressively cooled to 10 °C and rewarmed to 35 °C to identify vasoconstriction and vasodilatation; (ii) cold-induced vasodilatation (CIVD) test—hand immersed in 8 °C water for 30 min followed by spontaneous warming; (iii) cold sensitivity (CS) test—foot immersed in 15 °C water for 2 min followed by spontaneous warming. Cold sensory thresholds of the forearm and finger were also assessed.

Results

In the VT test, vasoconstriction and vasodilatation occurred at a warmer finger T _sk in AFD during cooling 21.2 (4.4) vs. 17.0 (3.1) °C, P = 0.034] and warming 22.0 (7.9) vs. 12.1 (4.1) °C, P = 0.002] compared with CAU. In the CIVD test, average SkBF during immersion was greater in CAU 42 (24) %] than ASN 25 (8) %, P = 0.036] and AFD 24 (13) %, P = 0.023]. Following immersion, SkBF was higher and rewarming faster in CAU 3.2 (0.4) °C min^?1] compared with AFD 2.5 (0.7) °C min^?1, P = 0.037], but neither group differed from ASN 3.0 (0.6) °C min^?1]. Responses to the CS test and cold sensory thresholds were similar between groups.

Conclusion

AFD experienced a more intense protracted finger vasoconstriction than CAU during hand immersion, whilst ASN experienced an intermediate response. This greater sensitivity to cold may explain why AFD are more susceptible to cold injuries.