The influences of age and caffeine on psychomotor and cognitive function

Rationale: The response to caffeine is affected by a number of factors, including age. Older subjects may be more sensitive to the objective effects than younger but report fewer subjective effects. Objective: This study assessed the influence of age on the effects of caffeine on a variety of psychomotor, cognitive and subjective tests. Methods: Forty-eight healthy subjects, male and female, were recruited, 24 in the age range 20–25 and 24 in the range 50–65 years. All subjects were regular moderate caffeine drinkers and were not withdrawn from caffeine before entry to the study. A double-blind parallel group design was used with two groups of 12 subjects in each age range. One group in each age range received placebo and the other 250 mg caffeine B.P. A range of tests was used to assess psychomotor, cognitive and subjective functioning before and 1 h post-treatment. Results: Before treatment, young subjects generally performed better than older on psychomotor and cognitive tests. On the subjective tests, however, older subjects rated themselves as more alert and less tired than the younger ones. After placebo, performance and alertness improved in the younger group but declined in the older. After caffeine there were improvements in psychomotor performance and cognitive functioning in both groups, particularly in offsetting declining performance over time in the older subjects. It also produced subjective improvements in alertness. One factor to emerge was that on most assessments older subjects were better earlier in the day whereas in younger subjects performance did not show the same magnitude of decline throughout the day. Conclusions: Caffeine induced small but significant improvements in vigilance and psychomotor performance.