CAFFEINE EFFECTS ON STRESS REACTIVITY

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Caffeine is the most widely consumed drug in the U.S., yet questions remain about the long-term health consequences of habitual consumption, especially with regard to cardiovascular diseases. Caffeine is known to raise blood pressure (BP), and research shows that it can potentiate cardiovascular and neuroendocrine stress reactivity. Both effects could increase the risks of developing cardiovascular diseases including hypertension and heart disease. The long-term objectives of this project are to investigate caffeine's effects, determine their implications for cardiovascular health and disease, and characterize the individuals who are most at risk. The specific aim of this application is to explore the potential cardiovascular health benefits that hypertensive individuals could obtain from the cessation of habitual caffeine consumption. Two hypotheses will be tested. (1) Caffeine cessation results in clinically significant reductions in BP in hypertensive individuals. (2) Caffeine cessation reduces activation of the neuroendocrine stress pathways that can mediate BP elevations. This clinical intervention trial includes groups of habitual coffee drinkers who have blood pressures in the high normal or mild hypertensive range and those who are currently receiving medication for established hypertension. Subjects will complete 7-day periods of ad lib caffeine consumption or experimental caffeine abstinence followed by a day of ambulatory monitoring. The effects of caffeine cessation on BP will be evaluated using both casual (office) and ambulatory measurements collected during the activities of the normal day. The effects of cessation on activation of neuroendocrine stress response pathways will be investigated in ambulatory measures of urinary catecholamine and cortisol excretion in the same environment. Hypertensive individuals could receive an immediate benefit if we learn that caffeine cessation reduces blood pressure. Those with high normal BP or mild hypertension might avoid or postpone the need for anti-hypertensive medications by adding caffeine cessation to a program of dietary and lifestyle management. Hypertensive patients already receiving pharmacological treatment might lower BP even more by caffeine cessation, further reducing their risk of long-term complications and perhaps reducing their need for medication. Although caffeine cessation may not be necessary for everyone, it may clearly contribute to BP management in hypertensive individuals and thereby reduce the risks for heart disease, stroke, and kidney disease that are the consequences of this disease.