Caffeine quick-study

Lee Ryan and his research group at the University of Arizona Department of Psychology recently studied the effects of coffee on 40 adults over age 65 who consider themselves to be people who work better in the morning. Each participant was accustomed to drinking a beverage containing caffeine on a daily basis but was randomly assigned to either a “regular” or “decaffeinated” group for the study.

Subjects from both groups attended morning and afternoon sessions, where they were tested using the California Verbal Learning Test protocol to obtain data on several measurements of memory. Before each session, participants were given either regular or decaffeinated coffee, depending on their group assignment, but were not told which group they had been assigned to. Sessions occurred 5–11 days apart, with some participants having the morning session first and some having the afternoon session first. All subjects received the same type of coffee at both sessions.

During each session, subjects were asked to recall a list of 16 words immediately after each of five consecutive presentations, an ability known as immediate free recall. They were then given an “interference list” of 16 other words and asked to recall the original list, an ability known as short-delay free recall. After a 20-minute delay, they were tested for long-delay recall and yes-no recognition of the learned words.

Both groups had about the same immediate free recall, but the caffeine group had an easier time with short-delay free recall. The caffeine group’s long-delay free recall did not vary with the time of day, but the control group’s performance declined significantly in the afternoon.

This study was not able to pin down an underlying mechanism for either the memory impairment effect or the stimulant’s mitigation of this effect, but the researchers speculate that caffeine or other stimulants may help older persons filter out distracting or irrelevant information or make it easier to encode new information.