Racial differences in hemodynamic responses to environmental thermal stress among adolescents

Area of Science:

• Cardiovascular Physiology
• Racial Health Disparities
• Adolescent Health

Background:

• Previous research indicates greater blood pressure (BP) responses to stressors in Black children compared to white children.
• The specific cardiac and vascular mechanisms underlying these BP reactivity differences remain unclear.
• It is unknown whether racial differences in vascular reactivity stem from excessive vasoconstriction or deficient vasodilation.

Purpose of the Study:

• To investigate the cardiac and vascular contributions to racial differences in BP reactivity.
• To determine if racial differences in vascular reactivity involve excessive vasoconstriction or deficient vasodilation.

Main Methods:

• Evaluated BP, heart rate, and impedance cardiography (pre-ejection period [PEP] and total peripheral resistance [TPR]) in healthy Black (n=76) and white (n=60) adolescents (mean age, 14.8 years).
• Assessed responses during passive exposure to a cold (8-10°C) and a heat (40-42°C) chamber.
• Utilized covariance analyses to explore underlying mechanisms.

Main Results:

• Black adolescents exhibited greater decreases in PEP and increases in TPR during cold exposure compared to white adolescents (P<0.05).
• No significant group differences in responses were observed during heat exposure.
• Covariance analyses suggested greater beta-adrenergic cardiac and alpha-adrenergic vasoconstrictive reactivity in Black adolescents during cold stress.

Conclusions:

• Black and white adolescents showed similar myocardial and vasodilatory responses to heat stress.
• Black adolescents demonstrated heightened myocardial and vasoconstrictive reactivity to cold stress.
• Racial differences in vascular reactivity appear to involve vasoconstriction rather than vasodilation, potentially contributing to hypertension risk in Black individuals.