Hypothalamic-pituitary-adrenocortical responses to psychological stress and caffeine in men at high and low risk for hypertension.

OBJECTIVE: This study examined pituitary-adrenocortical responses to dietary doses of caffeine (3.3 mg/kg, equivalent to 2 to 3 cups of coffee), alone and combined with behavioral stress, in men at high risk versus low risk for hypertension. A randomized, double-blind, caffeine-placebo crossover design was used. METHOD: Adrenocorticotropic hormone (ACTH) and cortisol levels in plasma were assessed at rest and in response to 60-minutes of continuous work on a mental stressor (arithmetic) and a psychomotor task (reaction time) on four test sessions held on separate days. RESULTS: Tasks alone caused greater ACTH and cortisol increases in high risk men than in the low risk group. Caffeine alone elevated ACTH and cortisol in both groups, with more immediate responses in the high risk group. Both groups showed significant ACTH and cortisol responses to caffeine plus tasks, with the high risk group showing more persistent elevations. The high risk group also showed the highest levels of ACTH and cortisol after caffeine plus tasks. CONCLUSIONS: These findings demonstrate for the first time the combined effects of caffeine plus stress on ACTH and demonstrate greater corticosteroid effects in hypertension-prone men. As such, they may have implications for the dietary use of caffeine during periods of stress and in those at risk for hypertension.

Acute blood pressure elevations with caffeine in men with borderline systemic hypertension.

Whether the vasoconstrictive actions of caffeine are enhanced in hypertensive persons has not been demonstrated. Thus, caffeine (3.3 mg/kg) versus placebo was tested in 48 healthy men (aged 20 to 35 years) selected after screening on 2 separate occasions. Borderline hypertensive men (n = 24) were selected with screening systolic blood pressure (BP) of 140 to 160 mm Hg and/or diastolic BP 90 to 99 mm Hg. Low-risk controls (n = 24) reported no parental history of hypertension and had screening BP < 130/85 mm Hg. Participants were then tested on 2 occasions after 12-hour abstinence from caffeine in each of 2 protocols; this required a total of 4 laboratory visits. Caffeine-induced changes in diastolic BP were 2 to 3 times larger in borderline subjects than in controls (+8.4 vs +3.8 mm Hg, p < 0.0001), and were attributable to larger changes in impedance-derived measures of systemic vascular resistance (+135 vs +45 dynes.s.cm-5, p < 0.004). These findings were consistent and reached significance in both protocols. The percentage of borderline subjects in whom diastolic BP changes exceeded the median control response was 96%. Consequently, whereas all participants exhibited normotensive levels during the resting predrug baseline, 33% of borderline subjects achieved hypertensive BP levels after caffeine ingestion. Thus, in borderline hypertensive men, exaggerated responses to caffeine were: selective for diastolic BP, consistent with greater vasoconstriction, replicated in 2 protocols, and representative of nearly all borderline hypertensives. We suspect that the potential for caffeine to stabilize high resistance states in susceptible persons suggests that its use may facilitate their disease progression, as well as hinder accurate diagnosis and treatment.

Effect of trait hostility on cardiovascular responses to harassment in young men.

Hostile individuals may experience more extreme and frequent episodes of anger than nonhostile persons and thus may have exaggerated physiological responses to their environments. Such responses may be associated with increased risk of cardiovascular disease. This study examined cardiovascular responses of 24 low- versus 21 high-hostile young men to a mental arithmetic task administered with and without provocation in 2 x 2 (groups x Tasks) repeated measure design. hostility classifications were based on weighted interview ratings of Potential for Hostility. As predicted, high-hostile men showed differentially greater heart rate, blood pressure, and rate-pressure product changes only in response to the task administered with harassment (ps < .05). Similarly, high-hostile men reported more distress, tenseness, irritation, and greater concentration during the harassing task, compared to low-hostile men (ps < .05). Also, the harassing task elicited greater increases in vascular resistance and greater increases in stroke volume for all subjects, relative to the neutral task (ps < .003). Results suggest that hostile persons faced with anger evoking situations may produce a constellation of exaggerated cognitive-emotional and cardiovascular responses consistent with increased risk of cardiovascular disease.

Borderline hypertensives produce exaggerated adrenocortical responses to mental stress.

Serum cortisol concentrations were compared in 18 borderline hypertensive (BH) and 20 normotensive (NT) men before and after mental stress. Two levels of demand, intermittent reaction time with brief rests and reaction time alternating continuously with mental arithmetic, were used in two consecutive protocols on different days in the laboratory. Continuous, but not intermittent, mental stress produced significant elevations in cortisol levels only in the BH subjects (p < .001). The continuous challenge produced slightly more self-reported distress in both groups than the intermittent condition, and performance on the mental arithmetic task was more strongly correlated with the cortisol response than was performance on the reaction time task, suggesting that the mental arithmetic task was a key contributor to the cortisol response. Therefore, adrenocortical activity appears sensitive to appropriate stressors in BH subjects. These results indicate the importance of including measures of adrenocortical function in studies of reactivity in subjects at high risk for hypertension.