Caffeine may potentiate adrenocortical stress responses in hypertension-prone men.

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Abstract
The effect of caffeine on blood cortisol levels and blood pressures was examined during rest and in response to a challenging psychomotor task in men with a low versus high risk of essential hypertension. Thirty-four healthy men ages 21-35 years were selected such that 17 were at high risk for hypertension (positive parental history and screening blood pressures 135/85-155-95 mm Hg) and 17 were at low risk (negative parental history and no pressures above 132/84 mm Hg). Testing consisted of quiet rest (20 minutes); oral placebo (grapefruit juice) or caffeine administration (3.3 mg/kg in grapefruit juice); rest during a postdrug absorption period (40 minutes); work on an unsignalled simple reaction time task (15 minutes); and quiet rest (20 minutes). Blood pressures were recorded at 2-minute intervals, and blood samples were withdrawn via an indwelling catheter at the end of the baseline, drug absorption, task, and recovery periods. The combination of task plus caffeine produced the highest blood pressures in men at risk for hypertension. Cortisol levels were found to be sustained during rest in members of the high risk group after they has consumed caffeine, whereas members of the low risk group showed a modest decline. The high risk subjects also showed a significant rise in cortisol during (+3.7 .mu.g/dl) and after (+4.0 .mu.g/dl) work on the reaction time task after caffeine consumption. In the low risk group, cortisol responses to caffeine were smaller (+2.2 .mu.g/dl or less) when compared with responses to the task after caffeine consumption. The results suggest that these men at high risk for hypertension were sensitive to caffeine and that caffeine combined with a demanding psychomotor challenge produced neuroendocrine signs of stress. These findings point toward the need for studies of the role of caffeine in modifying stress responses of targeted groups such as those at risk for hypertension.