Caffeine Affects Cardiovascular and Neuroendocrine Activation at Work and Home JAMES D. LANE,PHD, CARL F. PIEPER,DRPH, BARBARA G. PHILLIPS-BUTE,PHD, JOHN E. BRYANT,PHD, AND CYNTHIA M. KUHN,PHD Objective: This study investigated the effects of moderate doses of caffeine on ambulatory blood pressure and heart rate, urinary excretion of epinephrine, norepinephrine, and cortisol, and subjective measures of stress during normal activities at work and at home in the evening. Methods: Healthy, nonsmoking, habitual coffee drinkers (N = 47) participated in 3 days of ambulatory study. After a day of ad lib caffeine consumption, caffeine (500 mg) and placebo were administered double-blind in counter-balanced order on separate workdays. Ambulatory blood pressure and heart rate were monitored from the start of the workday until bedtime. Urinary excretion of catecholamines and cortisol was assessed during the workday and evening. Results: Caffeine administration significantly raised average ambulatory blood pressure during the workday and evening by 4/3 mm Hg and reduced average heart rate by 2 bpm. Caffeine also increased by 32% the levels of free epinephrine excreted during the workday and the evening. In addition, caffeine amplified the increases in blood pressure and heart rate associated with higher levels of self-reported stress during the activities of the day. Effects were undi- minished through the evening until bedtime. Conclusions: Caffeine has significant hemodynamic and humoral effects in habitual coffee drinkers that persist for many hours during the activities of everyday life. Further- more, caffeine may exaggerate sympathetic adrenal-medullary responses to the stressful events of normal daily life. Repeated daily blood pressure elevations and increases in stress reactivity caused by caffeine consumption could contribute to an increased risk of coronary heart disease in the adult population. Key words: caffeine, ambulatory monitoring, blood pressure, catecholamines, cortisol, occupational stress. DASH = Dietary Approaches to Stop Hypertension; DBP = diastolic blood pressure; HR = heart rate; SBP = systolic blood pressure. INTRODUCTION Caffeine is consumed daily by an estimated 85% of adults in the United States in coffee, tea, and soft drinks (1). This widespread consumption persists de- spite accumulating evidence that caffeine has potent stimulatory effects on the cardiovascular and neuroen- docrine systems that could have implications for health and disease (2). Laboratory studies over the last 20 years have consis- tently demonstrated that a caffeine dose equivalent to 2 to 3 cups of brewed coffee will raise resting blood pres- sure by 7 to 10 mm Hg when administered either to “caffeine-naive” individuals or to habitual coffee drink- ers after overnight abstinence (3–14). The observed blood pressure elevations reach a maximum 30 to 60 minutes after caffeine administration and persist for several hours. A smaller number of experimental studies have shown that caffeine can raise plasma levels of the major stress hormones, including the catecholamines epineph- rine and norepinephrine (3, 8) and cortisol (8, 15). These humoral effects indicate the activation of both the sym- pathetic adrenal-medullary and the hypothalamic pitu- itary adrenal-cortical components of neuroendocrine stress responses. The stimulatory effects of caffeine are similar to the physiological responses that are associated with the experience of stress, and the experimental evi- dence suggests that caffeine itself might act like a stressor when coffee and other caffeinated beverages are con- sumed in everyday life (4). In addition, the laboratory studies have also demonstrated that caffeine can inten- sify both cardiovascular and humoral responses to exper- imental stressors, amplifying the increases in cardiac output and skeletal muscle blood flow and the increases in plasma levels of epinephrine and cortisol elicited by challenging or threatening tasks (5, 6, 8, 10). These re- sults suggest that caffeine consumption may exaggerate the deleterious effects of stress in daily life and aggravate the damage to health that stress can cause. The laboratory studies have clearly demonstrated the kinds of effects that caffeine can have, but they have generally been limited to relatively short periods of data collection under well-controlled laboratory conditions. As such, these studies are less conclusive about the ef- fects of caffeine in the natural environment of everyday life, where it is so widely consumed in coffee, tea, and other caffeinated beverages. Ambulatory studies provide the opportunity for eco- logical validation of the hemodynamic and neuroendo- crine effects observed in the laboratory. Several studies have investigated how caffeine affects ambulatory mea- From the Department of Psychiatry and Behavioral Sciences (J.D.L., B.G.P.-B., J.E.B.), Department of Community and Family Medicine and The Center for the Study of Aging and Human Devel- opment (C.F.P.), and Department of Pharmacology (C.M.K.), Duke University Medical Center, Durham, NC. Address reprint requests to: James D. Lane, PhD, Department of Psychiatry and Behavioral Sciences, Box 3830, Duke University Medical Center, Durham, NC 27710. Email: jdlane@acpub.duke.edu Received for publication April 2, 2001; revision received August 8, 2001. DOI: 10.1097/01.PSY.0000021946.90613.DB 595 Psychosomatic Medicine 64:595– 603 (2002) 0033-3174/02/6404-0595 Copyright © 2002 by the American Psychosomatic Society