Evaluation of the effects of acute caffeine supplementation on selected cognitive domains in older women : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand

Abstract

Caffeine is the most frequently consumed psychoactive substance globally and has been shown to enhance various aspects of cognition, particularly in younger adults. Previous research has demonstrated that acute intake of low to moderate doses of caffeine (e.g., 100 mg to 300 mg) significantly improves lower-order cognitive functions such as processing speed and attention in younger adults. The impact of caffeine on higher-order cognitive domains such as memory and executive function remains unclear. Since older women experience age- and hormonal-related changes that may negatively affect cognition, this age group may be more likely to experience greater functional improvements in cognitive performance following caffeine supplementation compared to younger adults. This pilot study aims to evaluate the effect of acute caffeine supplementation on selected cognitive domains including processing speed, sustained attention, memory, and executive function, in post-menopausal women, aged 55 to 79 years. Twelve female participants (mean age ± SD = 63.75 ± 6.81 years) took part in a randomised placebo-controlled, double-blind, crossover study. Participants were asked to abstain from caffeine for 24 hours before each of three repeated cognitive testing sessions (separated by two-week intervals): baseline, 45 minutes post-ingestion of 100 mg caffeine, and 45 minutes post-ingestion placebo. Repeated measures ANOVA (treatment × time) indicated that 100 mg of caffeine supplementation significantly improved movement time (p = 0.04) in a five-choice reaction time (RTI) task, compared to placebo. There was a significant improvement over time for Rapid Visual Information Processing (RVP) sensitivity score (p = 0.04) and correct responses (p = 0.02), and Spatial Working Memory strategy score (p = 0.03). However, post-hoc analysis indicated no significant differences between caffeine and placebo supplementation. The key finding of the current study is 100 mg of caffeine supplementation significantly enhanced processing speed in older post-menopausal women but did not improve other cognitive processes including attention, memory, and executive function. In line with other research, caffeine supplementation may only affect performance on simpler tests requiring lower-order cognitive functions. This pilot study contributes to the growing body of research on caffeine and cognition, through a unique examination of older healthy women across a range of cognitive functions. However, further studies are necessary on a larger population scale and perhaps, utilising different doses of caffeine, to corroborate these findings.