Abstract

Seven men from twenty-one to twenty-five years of age received coffee, estimated to contain caffeine equivalent to a dose of 3 or 4 mgm. per kilogram body weight, or a like quantity of decaffeinated coffee (or bouillon), once daily for periods of three to eight weeks.

During the periods on coffee, the blood pressure was usually higher than that on decaffeinated coffee, the increase being distinct in some individuals and very slight or variable in others. The rise in blood pressure seldom exceeded 10 mm. Hg and was somewhat less in the latter weeks of the periods on coffee.

Motor function was changed throughout the periods on coffee. In one motor test (target), improvement in performance reached a maximum in the first two weeks on coffee, then decreased slightly, but was still apparent in the latter weeks (fifth to eighth) on coffee. In another motor test (acquired motor skill), performance was markedly impaired throughout the periods on coffee, the impairment of performance being almost as great in the latter weeks (fourth to seventh) as in the first part of the period.

When coffee was withdrawn, the blood pressure quickly returned to the level found after decaffeinated coffee, but in both motor tests, performance was impaired during the first week after withdrawal of coffee.

During the periods on decaffeinated coffee the blood pressure was not very different from that when a control beverage, bouillon, was administered. In the acquired motor skill (studies with the target test were not made), performance on decaffeinated coffee was essentially the same as that when bouillon was adminstered, or when no special beverages were taken.