The effect of caffeine on ambulatory blood pressure in hypertensive patients

Because the potential impact of habitual caffeine intake on blood pressure is a controversial issue, a study was carried out to explore the relationsh ip between caffeine and various humoral factors that could account for a co ffee-induced rise in blood pressure. Twenty-three hypertensive patients who refrained from caffeine far 2 to 3 weeks were given 250 mg oral caffeine p owder dissolved in water. Blood pressure was recorded every 15 min by blood pressure monitor. Caffeine blood level, renin and endothelin were measured before and 1, 2, 3, and 6 h after caffeine intake. Urinary electrolytes an d catecholamines were measured under caffeine influence (period I), and for the next 6 h (period II), A significant increase in systolic (P = .017) an d diastolic blood pressure (P = .023) occurred in 13 subjects who were 58 /- 10.4 years old. Nonresponders were younger (44.5 +/- 15.8 years). A stat istically significant decrease in heart rate was seen during the first hour after caffeine intake in both responders (P = .008) and nonresponders (P = .004). Marked diuresis and natriuresis were observed during period I in bo th groups. Renin and endothelin levels were unchanged. Although chronic stu dies point to development of tolerance to long-term caffeine ingestion, acu te studies like the one described are essential to obtain data on the immed iate effects that can be of practical importance, especially in the elderly . (C) 1998 American Journal of Hypertension, Ltd.