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.
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.
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.
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.
From the Veterans Affairs Medical Center (M.al'A., W.R.L., B.McK.) and Departments of Psychiatry and Behavioral Sciences (M.al'A. W.R.L.), and Medicine (T.L.W.), University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, and Millard Fillmore Hospitals (B.H.S., M.F.W.), Buffalo, New York.
Address reprint requests to: Mustafa al'Absi, PhD, Department of Behavioral Sciences, University of Minnesota, Duluth School of Medicine, Duluth, MN 55812-2487. E:mail: email@example.com.
Received for publication May 7, 1997; revision received November 18, 1997.