Caffeine is considered the most widely used pharmacologic substance in the United States, yet little research has been done on its cardiovascular effects at rest and during psychological and exercise stress. The present proposal describes studies designed to examine how caffeine (3.5 mg/kg, equal to 2-3 cup of coffee) affects cardiovascular function in men at low risk of developing hypertension and those showing early-to-mild hypertension (EH, defined as resting blood pressures of 140-160/90-95). Our research has shown that this dose of caffeine elevates blood pressure at rest by increasing the state for constriction of the peripheral blood vessels. We have also shown that during work on a demanding psychomotor task (unsignalled, simple reaction time with monetary bonuses), caffeine synergistically enhances heart rate, cardiac output, myocardial contractility, and indices of cardiac work. In normotensive men at high risk of developing essential hypertension, caffeine pressor effect in additive with the already elevated blood pressure. As a result, during psychological and aerobic exercise stress, this high risk group shows enhanced levels of blood pressure. At some point during aerobic exercise, 55% of the high risk subjects showed pressures in excess of 230/100 mmHg, considered to be abnormally high during exercise. The proposed studies will extend our work from men at risk to those showing true EH. Study I concerns caffeine's effects on responses to repeated psychomotor challenges separated by brief rests insufficiently long to allow recovery of baseline to occur. Study II tests caffeine's effects on continuous psychomotor and mental challenge with no rests. Study III examines caffeine's potential for producing excessive (greater than or equal to 230/100 mmHg blood pressure responses during graded aerobic bicycle exercise up through maximum exercise. Our use of impedance and nuclear imaging techniques for determining stroke volume and cardiac output permits an extensive characterization of the hemodynamic responses occurring during states of stress under caffeine. This research is of practical significance in providing useful information on caffeine's risk potential in hypertensive men.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL032050-05
Application #
3343278
Study Section
Behavioral Medicine Study Section (BEM)
Project Start
1984-12-01
Project End
1990-06-30
Budget Start
1989-08-01
Budget End
1990-06-30
Support Year
5
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Oklahoma Health Sciences Center
Department
Type
Schools of Medicine
DUNS #
937727907
City
Oklahoma City
State
OK
Country
United States
Zip Code
73117
Lovallo, William R (2011) Do low levels of stress reactivity signal poor states of health? Biol Psychol 86:121-8
Farag, Noha H; Whitsett, Thomas L; McKey, Barbara S et al. (2010) Caffeine and blood pressure response: sex, age, and hormonal status. J Womens Health (Larchmt) 19:1171-6
Lovallo, William R (2010) Cardiovascular responses to stress and disease outcomes: a test of the reactivity hypothesis. Hypertension 55:842-3
Lovallo, William R; Farag, Noha H; Vincent, Andrea S et al. (2006) Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women. Pharmacol Biochem Behav 83:441-7
Lovallo, William R; Yechiam, Eldad; Sorocco, Kristen H et al. (2006) Working memory and decision-making biases in young adults with a family history of alcoholism: studies from the Oklahoma family health patterns project. Alcohol Clin Exp Res 30:763-73
Rashid, Abdul; Hines, Mujahid; Scherlag, Benjamin J et al. (2006) The effects of caffeine on the inducibility of atrial fibrillation. J Electrocardiol 39:421-5
Farag, Noha H; Vincent, Andrea S; McKey, Barbara S et al. (2006) Sex differences in the hemodynamic responses to mental stress: Effect of caffeine consumption. Psychophysiology 43:337-43
Lovallo, William R; Whitsett, Thomas L; al'Absi, Mustafa et al. (2005) Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosom Med 67:734-9
Farag, Noha H; Vincent, Andrea S; Sung, Bong Hee et al. (2005) Caffeine tolerance is incomplete: persistent blood pressure responses in the ambulatory setting. Am J Hypertens 18:714-9
Farag, Noha H; Vincent, Andrea S; McKey, Barbara S et al. (2005) Hemodynamic mechanisms underlying the incomplete tolerance to caffeine's pressor effects. Am J Cardiol 95:1389-92

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