PHARMACOLOGY WITH A CUP OF COFFEE : DOUBLE-BLIND ANALYSIS FOR ARITHMETIC SKILL AND HEMODYNAMIC EFFECTS

Abstract

Effects of caffeine on aritlmetic skill test and hemodynamic effects were investigated after drinking caffeine-free or caffeine-containing (180mg) coffee. The development of tolerance in habitual coffee-drinkers was also examined. A double-blind study of 417 healthy medical university students (22.4±2.1 years old) was carried out. Ten rounds of the arithmetic tests were performed; the first four rounds before, and the subsequent six rounds after a coffee-break. Each round was composed of three 1-min arithmetic tests and two 1-min rests between the tests. The arittmetic skill per round was averaged. Simultaneously, heart rate and blood pressure were also measured once a round. The mean value of arithmetic skill at the 4th round before coffee-break was 86.7±3.9/ min (n=417). The heart rate and mean blood pressure were 73.7±3.3 beats/min and 85.7 ±3.8 mmHg. As compared with caffeine-free group (n=205), caffeine-containing groups had a significant enhancement of arithmetic skill at 45 to 60 min later. The mean blood pressure increased at 15 to 90 min, but the heart rate was unaffected. Simultaneously, the serum concentration of caffeine increased from 0.9±0.3 to 4.3±1.6 ptg/ml (n=12, P<0.01) at 45-60min after coffee (180mg caffeine)-drinking. Habitual coffee-drinkers reduced the stimulations of arithmetic skill and mean blood pressure, as compared with non- habitual coffee-drinkers. These results indicate that a cup of coffee (containing 180 mg caffeine) enhances the arithmetic skill and modulates the hemodynamic actions, presumably resulting from stimulation of the central and sympathomimetic nervous systems. A tolerance to caffeine's actions also develops in habitual coffee-drinkers.