CAFFEINE IMPROVES MEMORY PERFORMANCE DURING DISTRACTION IN MIDDLE-AGED, BUT NOT IN YOUNG OR OLD SUBJECTS

The present study evaluated the effect of caffeine (225 mg) on cogniti ve performance in young, middle-aged, and old subjects in a placebo-co ntrolled parallel groups design (n = 60). Groups were matched for leve l of education and sex. Positive effects of caffeine, as compared to p lacebo, were found in middle-aged subjects in the first trial of the w ord learning test. In contrast, caffeine had negative effects on the s peed of searching short-term memory in young subjects. Caffeine had no effect on the intercept, which is an indicator for sensorimotor speed , of a memory scanning task. The middle-aged subjects appeared to regu larly consume twice as much caffeine as the young and old subjects. Th ese results were similar to earlier findings in a large population stu dy. Although statistical analyses with habitual caffeine consumption a s a covariate did not yield different results, a caffeine withdrawal e ffect was hypothesized to be responsible for the reduced cognitive per formance of middle-aged subjects receiving placebo. The habitual use o f large amounts of caffeine by middle-aged subjects may be a means to overcome the age-related decrease in cognitive functioning that is cau sed by changes in information processing. (C) 1998 John Wiley & Sons, Ltd.