Cardiovascular reactivity with caffeine and stress in black and white normotensive females.

Forty-eight healthy, young, normotensive black and white women, half with and half without a parental history of hypertension, were studied using a double-blind, randomized design. Systolic (SBP) and diastolic (DBP) blood pressures and heart rate (HR) were recorded in response to 250 mg of caffeine vs placebo (3 mg) during rest and during a stressful mental arithmetic task. Results indicated no racial or parental history differences in response to caffeine or to stress. Surprisingly, our female subjects evidenced a small drop in SBP (1 mm Hg) and a decline in HR (5 bpm), and, as expected, they demonstrated a rise in DBP of 6 mm Hg in response to caffeine. The effects of caffeine on SBP and HR were contingent on the experimental condition such that the difference in SBP and HR between the high vs low dose of caffeine was significant only under the caffeine plus psychological stress condition. These effects were only partially consistent with those previously observed in males. Previous evidence of significantly greater DBP pressor effects when caffeine is consumed under stressful conditions was confirmed. However, in this study, the caffeine alone condition had little effect on SBP reactivity and promoted a decrease in HR reactivity. The results are discussed in relation to previous research on males, and recommendations for future research are offered.