Whitsett T L, Manion C V, Christensen H D
Am J Cardiol. 1984 Mar 15;53(7):918-22. doi: 10.1016/0002-9149(84)90525-3.
This study evaluated the cardiovascular effects and elimination kinetics of coffee and caffeine in 54 volunteers selected according to 3 gradations of daily caffeine consumption, cigarette smoking status and the presence of caffeine intolerance. After 24 hours of caffeine abstinence, subjects received coffee and 2.2 mg/kg of caffeine (equivalent to 2 cups of coffee). Blood pressure, heart rate, systolic time intervals and plasma concentrations of caffeine were measured before and at timed intervals after coffee and caffeine. There were no differences in response to coffee and caffeine. The average systolic/diastolic blood pressure increased 9/10 mm Hg. The maximal decrease in heart rate averaged 10 beats/min, and there were small increases in the systolic time intervals. There were no cardiovascular differences among the various groups. Caffeine in the smokers and heavy caffeine users had a shorter half-life (3.2 and 4.1 hours) than that in nonsmokers and nonusers (5.1 and 5.3 hours). In the caffeine-intolerant group it had a longer half-life, while the cardiovascular effects were similar to those of the other groups. Thus, irrespective of the amount of daily caffeine consumption, smoking status or caffeine intolerance, the cardiovascular responses were similar and tolerance, if present, was gone by 24 hours.
本研究评估了咖啡和咖啡因对54名志愿者的心血管影响及消除动力学，这些志愿者根据每日咖啡因摄入量、吸烟状况和咖啡因不耐受情况分为3个等级。在戒断咖啡因24小时后，受试者饮用咖啡并摄入2.2毫克/千克的咖啡因（相当于两杯咖啡）。在饮用咖啡和咖啡因之前及之后的特定时间间隔测量血压、心率、收缩期时间间期和咖啡因的血浆浓度。对咖啡和咖啡因的反应没有差异。平均收缩压/舒张压升高9/10毫米汞柱。心率最大降幅平均为每分钟10次，收缩期时间间期略有增加。不同组之间没有心血管差异。吸烟者和大量咖啡因使用者体内咖啡因的半衰期（分别为3.2小时和4.1小时）比不吸烟者和非大量使用者（分别为5.1小时和5.3小时）短。在咖啡因不耐受组中，其半衰期更长，而心血管效应与其他组相似。因此，无论每日咖啡因摄入量、吸烟状况或咖啡因不耐受情况如何，心血管反应相似，且如果存在耐受性，24小时后也会消失。
