OBJECTIVES: As concern over caffeine-containing pharmaceutical ingredients prompted a regulatory review in Australia, we investigate how response to caffeine varies by age-group.

METHODS: An opportunity sample of London, United Kingdom, residents was recruited for the experiment. Participants completed an online reaction time test at pre-determined intervals before and at 5 minutes, 30 minutes,1 hour, 2 hours and 5 hours after drinking a 300ml can of sugar-free caffeinated Pepsi Max. At each interval, the reaction time test was completed three times in quick succession and the mean time calculated by the reaction time software was recorded.

RESULTS: The 9-19 age-group had the fastest average reaction time overall and little change from baseline (279ms, 274ms, 275ms, 275ms, 276ms, 270ms). Average reaction time in the 20-29 age-group started to fall at 5 minutes and only began to rise at the 2-hour measurement after caffeine consumption. The 30-39 age-group on average experienced a decrease in reaction time only 30 minutes after caffeine intake and the effect began to wane after 1 hour. The 40-49 age-group had a steady decrease in reaction time until 1 hour after caffeine consumption (from 355ms to 298ms). Reaction time in the 50+ age-group declined from baseline only for the first 30 minutes, before starting to rise. All age-groups except 30-39-year-olds had a lower reaction test time at 5 hours compared to baseline.

CONCLUSIONS: Reaction time improved across age-groups after caffeine consumption, but the magnitude and longevity of impact varied. While further testing on larger randomized samples is needed, this experiment’s results could inform research into drug caffeine content requirements: younger people, with faster metabolisms and fewer years of pre-existing exposure to caffeine, were found to experience a positive caffeine impact on reaction times faster than other age groups, but the magnitude of improvement in reaction time was lower.