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Impact of caffeine and psychological stress on blood pressure in black and white men.

The purpose of this study was to examine the effects of caffeine and psychological stress on systolic blood pressure (SBP) and heart rate (HR) in 40 healthy Black and White male regular coffee drinkers. Half the subjects had a positive family history of hypertension (FH+), and half did not. The effects of 250 mg of caffeine versus placebo (3 mg) in decaffeinated coffee were compared in a within-subject, double-blind, cross-over design. SBP and HR were measured at rest, after caffeine ingestion, during mental arithmetic stress, and during recovery. Results confirmed previous findings with White men that a moderate dose of caffeine produced significant increases in SBP and little effect on HR and that the pressor effects of caffeine and stress combined additively. Contrary to expectations, no overall race or family history differences in SBP levels or in SBP reactivity were observed. FH+ Blacks, however, evidenced slower SBP recovery than Whites. Whites evidenced higher overall HR levels than blacks, but this difference was not specific to caffeine or to mental stress. Mechanisms of racial differences in reactivity underlying differential risk for hypertension are discussed, as well as the utility of caffeine as a pharmacologic probe for such differences.