THE EFFECT OF CAFFEINE, COFFEE AND DECAFFEINATED COFFEE UPON BLOOD PRESSURE, PULSE RATE AND SIMPLE REACTION TIME OF MEN OF VARIOUS AGES

¹ From the Laboratory of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan

Sixteen men in the third, sixth, seventh and eighth decades of life received coffee or caffeine plus decaffeinated coffee on one or two days of each week and decaffeinated coffee on the intervening days for a period of from three to fourteen weeks.

Decaffeinated coffee did not affect reaction time, i.e., the response remained uniform from day to day and did not change when the size of the dose was varied. Coffee or caffeine in dosages equal to or exceeding 2 mgm. of caffeine per kgm. of body weight altered reaction time, each dose frequently exerting an influence for twenty-four hours. With doses equivalent to 3 or 4 mgm. of caffeine per kilogram the reaction time to 3 hours after the drugs was from 2 to 6 per cent shorter than that after decaffeinated coffee, but on the day following the dose it was frequently longer. The response did not change throughout one or two months of experimentation and was essentially the same in the elderly men as in the young men. With doses equivalent to 2 mgm. of caffeine per kilogram the reaction time was shorter than that after decaffeinated coffee in certain individuals and longer in others. The variability (standard deviation of the average reaction time) after coffee or caffeine was generally not as great as that after decaffeinated coffee.

One or two hours after coffee (doses equivalent to 3, 4 or 4.5 mgm. of caffeine per kilogram) the blood pressure was higher (5 to 10 mm. Hg) and the pulse rate, slower (5 per minute) in certain individuals and faster in others than the blood pressure and the pulse rate after decaffeinated coffee. The changes in blood pressure and pulse rate elicited by coffee were more distinct in the older men than in some of the young men.