Abstract

HABITUAL CAFFEINE CONSUMPTION, GENDER AND SELECTIVITY IN ATTENTION AND MEMORY, MOOD, AND CARDIOVASCULAR FUNCTION

Andrew P. Smith*, PhD

ABSTRACT

Background: The acute effects of caffeine have been widely studied, but less is known about the effects of habitual consumption, with the limited literature showing conflicting results. Research has investigated associations between habitual caffeine consumption and physical and mental health. The present study examined whether the level of habitual caffeine consumption modified selectivity in memory and attention, mood and cardiovascular function. The effects of gender were also investigated, and the effects of smoking and alcohol consumption covaried. Method: One hundred and twenty university students (50% female) participated in the study. Measurements were taken in the morning between 9.30 and 11.30 am, and questionnaires measuring health-related behaviours were completed. Blood pressure and heart rate were recorded, mood was rated before and after the battery of performance tasks, and tests measuring selectivity memory and attention were performed. Results: The multivariate effects of gender and high/low caffeine consumption (based on a median split of 125mg) were significant. There were no significant multivariate effects of smoking and alcohol consumption, and the gender x caffeine interaction was not significant. Systolic blood pressure was greater in males. Females showed more Stroop colour-word interference. High caffeine consumption was also associated with a smaller recall priority effect. Conclusion: The present analyses showed that both gender and caffeine consumption had little effect on mood. Systolic blood pressure was greater in males, whereas females showed greater distraction from an irrelevant colour word. Caffeine consumption did not have a significant effect on most of the measures. The exception was the recall priority task, which measures resource allocation to high and low-priority components in memory. High caffeine consumption was associated with a reduced priority effect, which is often found in low alertness states. These results need to be extended by examining a more detailed profile of caffeine consumers and other measures of selective attention and memory.

Keywords: Caffeine; University students; Heart rate; Blood pressure; Mood; Selective Attention; Biased probability choice reaction time; Stroop Task; Task priority; Category Instances.